Tag Archives: atom

What are the strong chemical bonds?

Everything around you is made of chemicals. And that’s only possible because those chemicals interact and bind together. Exactly how and why they do this depends on their nature but, in general, there are two kinds of interactions that keep them close: “primary” (or ‘strong’) and “secondary” (or weak) interactions.

Image credits Thor Deichmann.

These further break down into more subcategories, meaning there’s quite a lot of ground to cover. Today, we’ll be looking at the strong ones, which are formed through the transfer of electrons or electrostatic attraction between atoms.

As we go forward, keep in mind that atoms interact in order to reduce their energy levels. That’s what they get out of bonding to other chemicals, and they will do so until they find a bond-mate which will bring perfect balance to their lives; kinda like people do.

An atom’s stable configuration, the state all atoms tend towards, is known as its noble gas configuration. Noble gases make up the last column on the periodic table’s rightmost side, and they’re extremely or completely non-reactive chemically (they don’t need to interact because they have internal equilibrium).

Strong bonds are the most resilient ties atoms or molecules can forge with their peers. The secret to their strength comes from the fact that primary interactions are based on an atom’s valence. The valence number signifies how many electrons zipping around an atom’s core can be ‘shared’ with others. The overwhelming majority of a substance’s chemical behavior is a direct product of these electrons.

Covalent bonds

The first type of strong interactions we’ll look at, and the most common one, is the covalent bond. The name, “co-valence” sums up the process pretty well: two atoms share some or all of their valence electrons, which helps both get closer to equilibrium. This type of bond is represented with a line between two atoms. They can be single (one line), double (two lines), or triple (three lines).

File:Covalent Organic Frameworks (space-filling diagram).jpg
Covalent bonds are especially important in organic chemistry. Image via Wikimedia.

In essence, what happens inside a covalent bond is that you have an atom starved of electrons (positively charged) and one who has too many electrons (negatively charged). Neither of them wants to keep going on like that because their internal imbalance of electrical charges makes them unstable. When put close to each other, they will start behaving like a single ‘macroatom’ — their electrons will start orbiting around both.

These shared orbits are what physically keeps the atoms together. The atom with too many electrons only ‘has’ them for half the time, and the one with too few gets to have enough half the time. It’s not ideal, but it’s good enough and it requires no changes to the structure of the atom (which is just dandy if you ask nature).

Things get a bit more complicated in reality. Electrons don’t zip around willy-nilly, but need to follow certain laws. These laws dictate what shape their orbits will take (forming ‘orbitals’), how many layers of orbitals there will be and how many electrons each can carry, what distance these orbitals will be from the nucleus, and so on. In general, because of their layered structure, only the top-most orbitals are involved in bonding (and as such, they’re the only ones giving elements their chemical properties). Keep in mind that orbitals can and do overlap, so exactly what ‘top-most’ means here is relative to the atom we’re discussing.

Orbitali, Lipire, Atom, Moleculă, Legarea Covalentă
A 3D rendering of electron orbitals. Image via Pixabay.

But to keep it short, covalent bonding involves atoms pooling together their free electrons and having them orbit around both, using each other’s weakness to make the pair stronger.

Covalent bonds are especially prevalent in organic chemistry, as it is the preferred way carbon bonds to other elements. The products they form can exist in a gas, liquid, or solid state, whereas the following two types can only produce solid substances.

Ionic bonds

Next are ionic bonds. Where covalent bonds involve two or more atoms sharing electrons, ionic bonds are more similar to donations. This type of chemical link is mediated by an electrostatic charge between atoms (negatively charged particles attract positively-charged ones). The link is formed by one or more electrons going from the donor to the receiver in a redox (oxidation-reduction) reaction; during this type of reaction, the atoms’ properties are changed, unlike in covalent bonds. Ionic bonds generally involve a metal and a nonmetal atom.

File:Sodium chloride - crystals.jpg
Table salt crystals. Salts are formed from ionic bonds. Image via Wikimedia.

Table salt is a great example of a compound formed with ionic bonds. Salt is a combination of sodium and chlorine. The sodium atom will cede one of its electrons to the chlorine, which will make them hold different electrical charges; due to this charge, the atoms are then strongly drawn together.

It again ties into equilibrium. Due to the laws governing electron orbitals, there are certain configurations that are stable, and many others that are not. At the same time, atoms want to achieve electrostatic neutrality, as well. In an ionic bond, an atom will take an increase in its electrostatic energy (it will give or take negative charge) to lower its overall internal imbalance (by reaching a stable electron configuration) because that’s what lowers its energy the most.

Covalent bonds for the most part take place between atoms with the same electrostatic properties, and there’s no direct transfer of electrons because that would increase the overall energy levels of the system.

Ionic bonds are most common in inorganic chemistry, as they tend to form between atoms with very different electrostatic properties and (perhaps most importantly) ionic compounds are always soluble in water. However, ionic compounds such as salts do have a very important part to play in biology.

The main difference between ionic and covalent bonds is how the atoms involved act after they link up. In a covalent bond, they are specifically tied to their reaction mates. In an ionic bond, each atom is surrounded by swarms of atoms of opposite charge, but not linked to one of them in particular. Atoms with a positive charge are known as cations, while those with a negative charge are anions.

Another thing to note about ionic bonds is that they break if enough heat is applied — in molten salts, the ions are free to move away from each other. They also quickly break down in water, as the ions are more strongly attracted to these molecules than each other (this is why salt dissolves in water).

Metallic bonds

Microstructure of VT22 steel (titanium wrought alloy) after quenching. Image via Wikimedia.

If the name didn’t give it away, this type of chemical bond is the hallmark of metal and metallic alloys. It’s not the only type of bond that they can form, even between pure metals, but it’s almost always seen in metals.

Chemically speaking, metals are electron donors — they need to shed electrons to reach equilibrium. Because of the nature of these atoms, their electrons can move around between atoms, forming ‘clouds’ of electrons. These detached electrons are referred to as being ‘delocalized’.

This type of bond shares properties of both ionic and covalent bonds. In essence, every metal atom needs to give away electrons to be stable (thus behaving like a cation). But because it’s surrounded by other metal atoms (meaning other cations), there’s nobody who wants to accept that electrical charge. So the electrons get pooled together and everyone gets to have them some of the time (thus forming a covalent bond). You can think of it as an ionic bond where the atomic nuclei form the cations and the electrons themselves the anions. Another way to look at it, although this is more of an abstraction used to illustrate a point, is that all the atoms involved in a metallic bond share an orbital.

Keep in mind that this ‘sea of electrons’ theory is a model of the process — it’s oversimplified and not a perfect representation of what’s actually going on, but it’s good enough to give you a general idea of how metallic bonds work.

Because metallic bonds share properties of both ionic and covalent bonds they create crystalline bonds (like salts) while still remaining malleable and ductile (unlike most other crystals). Most of the physical properties we seek in metals are a direct product of this structure. The cloud of delocalized electrons acts as a binder, holding the atoms together. It also acts as a cushion, preventing mechanical shock from fracturing the structure. When blacksmiths hammer iron or steel, they rearrange the atomic cores. Electrons can still move around them, like water around the rocks in a stream, and help hold everything together during the process.

Metallic bonds have the lowest bond energy of the types we’ve seen today — in other words, they’re the most stable.

Chemistry often gets a bad rep for being that boring subject with math and mixing of liquids. So it’s easy to forget that it literally holds the world together. The objects around us are a product of the way their atoms and molecules interact. Our knives can cut the food on our plates because billions of atoms inside that knife hold onto each other for dear life, and those in food don’t. Diamonds cut through solid stone because carbon atoms can bind to other carbon atoms in structures that are stronger than almost anything else we’ve ever seen. Our cells and tissues are held together by the same interactions. We’re alive because water molecules are shaped in such a way as to make them universal solvents.

We’re still very much working with models here — our understanding of the ties that bind is still imperfect. But even these models can help us appreciate the immense complexity hidden in the most mundane objects around us.

The Plum Pudding Model: how a flawed idea was instrumental in our understanding of the atom

In 1904, British physicist J. J. Thomson proposed his idea of what the atom looked like. It was an unusual, but plausible construction that was well-received in the scientific community — for a time.

A few years earlier, Thomson had discovered the electron and he was trying to reconcile two of the known properties of the atom: that electrons have a negative charge, and the overall atom is neutral. If electrons are negative and the atom is neutral, then something must be positive. So Thomson came up with a distribution that made sense at the time — in quaint British fashion, he called it the Plum Pudding Model.

The Plum Pudding Model has electrons surrounded by a volume of positive charge in which negative-charge electrons are embedded. It was relatively short-lived: in 1911, Ernest Rutherford published results showing a small nucleus of positive charge, instead of a large mass around the electrons.

Small things that make up everything

The idea that matter is made of atoms goes back a long time, but was abandoned for two thousand years.

The Greek philosopher Democritus, born around the year 460 BC, promoted what was regarded by many as a crazy idea: everything we see around us is made of small, individual constituents. He called these constituents “atomos”, or atoms, as we’d call them in English.

Some of the ideas Democritus had turned out to be remarkably intuitive. He believed that atoms are invisible to the human eye, but they do have a geometry. They are always in motion, are separated by void, and individual atoms are indestructible — very close to what we know to be true today.

Although some philosophers still considered it, the atomic idea of Democritus was largely abandoned for centuries, particularly as it was disregarded by his followers Plato and Aristotle. Plato, who believed that all matter is made of the four elements (earth, fire, wind, and water), reportedly hated Democritus so much that he wished all his books were burned. Nevertheless, Democritus is considered by some the “father of modern science“, his approach being closer to science than to philosophy, as was the case of Plato.

For many centuries, few people paid much attention to the atomic theory of Democritus. However, that changed dramatically in the 20th century, as new scientific discoveries were being made. At some point, philosopher and polymath Bertrand Russel wrote that this atomic theory “was remarkably like that of modern science, and avoided most of the faults to which Greek speculation was prone.”

The atomic theory had once again come into attention.

All lights on atoms

Near the end of the 18th century, English researcher John Dalton was struggling to explain some experimental results. Dalton, who also studied color blindness (hence the term “daltonism“), found that no matter how you combine chemical elements, the total mass in the reaction remains the same. He and other chemists also noted that water absorbs different gases in different proportions — for example, water absorbs carbon dioxide far better than it absorbs nitrogen.

He proposed that each chemical element is composed of atoms of a single, unique type. These atoms cannot be altered or destroyed by chemical means, but they can combine to form more complex structures — strikingly similar to what Democritus had proposed.

This was the dominant school of thought for about one century, until one J. J. Thomson came along.

Various atoms and molecules as depicted in John Dalton’s A New System of Chemical Philosophy (1808).

Raisins, not plums

Rather ironically, the ‘Plum Pudding Model’ is actually a misnomer. It uses an archaic meaning of the British ‘plum pudding’, which is actually a cake made with raisins (in pre-Victorian time, ‘plum’ was used for raisins). But this old-school cake would take yet another meaning.

By the early 1900s, famous researchers such as Amadeo Avogadro, Robert Brown, and even Albert Einstein had explored the flaws of the Dalton model — but atoms were still thought to be the smallest possible division of matter until Thomson’s experiments in 1897.

Through experimentation, Thomson found that a cathode ray can be deflected by an electric field. This means that instead of being light, this cathode ray had to be something else, which Thomson correctly deduced to be a flow of electrons. In other words, he had found one of the building blocks of atoms: a negatively charged electron. It was a particle unlike any previously known, and Thomson took this time before he could prove his discovery beyond the shadow of a doubt.

He even measured the mass-to-charge ratio of electrons, finding that they are 1800 times smaller than hydrogen, the smallest atom. There was no doubt about it: atoms were divisible, and these electrons were negative in charge. Which means something must also be positive in atoms.

A replica of J. J. Thomson’s cathode rays which helped discover the electron. Image credits: Cambridge University.

If you want to bake a plum cake, you must first invent the universe

Atoms are neutral in electric charge. Sure, there are ions which are positively or negatively charged, but technically speaking, atoms are neutral. So if electrons are negative, they must have a positive counterpart.

Since Thomson found electrons to be so small, whatever that positive thing must be should be relatively big. So he considered three scenarios:

  • Each negatively charged electron has a positively charged particle that follows it everywhere;
  • Electrons orbit a region of positive charge with the same magnitude as the total charge of all electrons;
  • The negative electrons occupy a space that is uniformly and positively charged.
A plum pudding — delicious from the first atom to the last.

He selected the latter as the most likely of the three. He submitted his ideas to the 1904 edition of the Philosophical Magazine, where Thomson wrote:

… the atoms of the elements consist of a number of negatively electrified corpuscles enclosed in a sphere of uniform positive electrification, …

This theory was embraced by physicists, who started devising experiments to learn even more about atoms, based on this configuration.

Ironically, it was these exact experiments that ended up disproving the Plum Pudding model.

Disproving the cake, and raisin’ a new theory

Neutrons hadn’t been discovered at the time, but the fundamental structure of the model has remained largely similar.

Funny enough, Thomson’s model was disproved by one of his students, Ernest Rutherford. This just goes to show how influential Thomson’s work and lab were at the time.

Rutherford’s experiments showed that the positive charge is concentrated towards the center of the atom, in what seemed to be an atomic nucleus. Rutherford immediately suspected a planetary model of the atom, where the nucleus is like a star, and the electrons orbit around it like planets.

But there was a problem, and a big one at that: it contradicted classical mechanics.

In Rutherford’s envisioned model, the electron would release electromagnetic radiation while orbiting a nucleus. This means it would lose energy in the process, spiraling closer to the nucleus, and collapsing on the atom in picoseconds. This model is a disaster because it would suggest that all atoms are unstable, which is clearly not the case. It was only when Niels Bohr’s explanation came along that this model could find its ground.

According to Both, the electron is able to revolve in certain stable orbits around the nucleus without radiating any energy, contrary to what classical electromagnetism suggests. Rutherford and Bohr presented their model together, and although our understanding of the atom has changed several times and we’ve learned far more about atomic and subatomic particles, this model is still widely used, at least in non-academic circles.

Why bother learning about the Plum Pudding model

It’s easy to disregard the Plum Pudding model as flawed and never look at it again. But there’s a reason why physics classes still feature this model, and it’s not just for historical reference.

The idea is that if we want to truly learn something, and not just memorize it, it helps to build a process. If we go through the stages of how physicists first learned about the atoms, what theories they had, and how these theories were proven or disproven, we gain a much better understanding. That’s why we learn about the Plum Pudding model, because there can be value even in discredited ideas.

Rest assured: as science and technology progress, no doubt some of the models we use today will turn out to be flawed, and people will still learn about them.

We’re still learning new things about the atoms’ constituents and their structure, and we’ll be learning more for the foreseeable future. Science is rarely about finding an ultimate, finite truth — instead, science is about adding more and more layers of understanding and building approximate models. Thomson’s model was one of these approximations: it was far from perfect, in fact it was thoroughly disproven — and yet, it played an important role, as it paved the way for more, better discoveries to be made.

This is what science is all about.


An AI recreated the periodic table from scratch — in a couple of hours

A new artificial intelligence (AI) program developed at Stanford recreated the periodic table from scratch — and it only needed a couple of hours to do so.


If you’ve ever wondered how machines learn, this is it — in picture form. (A) shows atom vectors of 34 main-group elements and their hierarchical clustering based on distance. The color in each cell stands for value of the vector on that dimension.
Image credits Zhou et al., 2018, PNAS.

Running under the alluring name of Atom2Vec, the software learned to distinguish between different atoms starting from a database of chemical compounds. After it learned the basics, the researchers left Atom2Vec to its own devices. Using methods and processes related to those in the field of natural language processing — chiefly among them, the idea that the nature of words can be understood by looking at other words around it — the AI successfully clustered the elements by their chemical properties.

It only took Atom2Vec a couple of hours to perform the feat; roughly speaking, it re-created the periodic table of elements, one of the greatest achievements in chemistry. It took us hairless apes nearly a century of trial-and-error to do the same.

I’m you, but better

The Periodic Table of elements was initially conceived by Dmitri Mendeleev in the mid-19th century, well before many of the elements we know today had been discovered, and certainly before there was even an inkling of quantum mechanics and relativity lurking beyond the boundaries of classical physics. Mendeleev recognized that certain elements fell into groups with similar chemical features, and this established a periodic pattern (hence the name) to the elements as they went from lightweight elements like hydrogen and helium, to progressively heavier ones. In fact, Mendeleev could predict the very specific properties and features of, as yet, undiscovered elements due to blank spaces in his unfinished table. Many of these predictions turned out to be correct when the elements filling the blank spots were finally discovered.

“We wanted to know whether an AI can be smart enough to discover the periodic table on its own, and our team showed that it can,” said study leader Shou-Cheng Zhang, the J. G. Jackson and C. J. Wood Professor of Physics at Stanford’s School of Humanities and Sciences.

Zhang’s team designed Atom2Vec starting from an AI platform (Word2Vec) that Google built to parse natural language. The software converts individual words into vectors (numerical codes). It then analyzes these vectors to estimate the probability of a particular word appearing in a text based on the presence of other words.

The word “king” for example is often accompanied by “queen”, and the words “man” and “woman” often appear together. Word2Vec works with these co-appearances and learns that, mathematically, “king = a queen minus a woman plus a man,” Zhang explains. Working along the same lines, the team fed Atom2Vec all known chemical compounds (such as NaCl, KCl, and so on) in lieu of text samples.

It worked surprisingly well. Even from this relatively tiny sample size, the program figured out that potassium (K) and sodium (Na) must be chemically-similar, as both bind to chlorine (Cl). Through a similar process, Atom2Vec established chemical relationships between all the species in the periodic table. It was so successful and fast in performing the task that Zhang hopes that in the future, researchers will use Atom2Vec to discover and design new materials.

Future plans

“For this project, the AI program was unsupervised, but you could imagine giving it a goal and directing it to find, for example, a material that is highly efficient at converting sunlight to energy,” he said.

As impressive as the achievement is, Zhang says it’s only the first step. The endgame is more ambitious — Zhang hopes to design a replacement for the Turing test, the golden standard for gauging machine intelligence. To pass the Turing test, a machine must be capable of responding to written questions in such a way that users won’t suspect they’re chatting with a machine; in other words, a machine will be considered as intelligent as a human if it seems human to us.

However, Zhang thinks the test is flawed, as it is too subjective.

“Humans are the product of evolution and our minds are cluttered with all sorts of irrationalities. For an AI to pass the Turing test, it would need to reproduce all of our human irrationalities,” he says. “That’s very difficult to do, and not a particularly good use of programmers’ time.”

He hopes to take the human factor out of the equation, by having machine intelligence try to discover new laws of nature. Nobody’s born educated, however, not even machines, so Zhang is first checking to see if AIs can reach of the most important discoveries we made without help. By recreating the periodic table, Atom2Vec has achieved this goal.

The team is now working on the second version of the AI. This one will focus on cracking a frustratingly-complex problem in medical research: it will try to design antibodies to attack the antigens of cancer cells. Such a breakthrough would offer us a new and very powerful weapon against cancer. Currently, we treat the disease with immunotherapy, which relies on such antibodies already produced by the body; however, our bodies can produce over 10 million unique antibodies, Zhang says, by mixing and matching between some 50 separate genes.

“If we can map these building block genes onto a mathematical vector, then we can organize all antibodies into something similar to a periodic table,” Zhang says.

“Then, if you discover that one antibody is effective against an antigen but is toxic, you can look within the same family for another antibody that is just as effective but less toxic.”

The paper “Atom2Vec: Learning atoms for materials discovery,” has been published in the journal PNAS.

Atomium ball.

What are isotopes

Atoms are the building blocks of matter. The screen you’re reading this on, the brain you’re reading with, they’re all very organized groups of atoms. They interact in specific ways, obeying specific rules, to maintain the shape and function of objects.

None of it works, however, unless the right atoms are involved. If you try to put the wrong ones into a protein or water molecule, it breaks apart. It’s like trying to cobble together a picture using pixels of the wrong colors.

Atomium ball.

Image in Public Domain.

Given how rigorous chemistry is on this, it’s surprising to see how much variety these ‘right’ atoms can get away with. Each element on the periodic table encompasses whole families of atoms who behave the same despite some important differences — isotopes.

What are isotopes?

Isotopes are atom families that have the same number of protons, but different numbers of neutrons. The term is drawn from ancient Greek words isos and topos, meaning ‘equal place’, to signify that they belong to the same elements on the periodic table.

Atoms are made of a dense core (nucleus) orbited by a swarm of electrons. The protons and neutrons that form the core represent virtually all of an atom’s mass and are largely identical except for their electrical charges — protons carry a positive charge, while neutrons don’t have any charge. The (negatively charged) electron envelope around the core dictates how atoms behave chemically.

The kicker here is that since neutrons carry no charge, they don’t need an electron nearby to balance them out. This renders their presence meaningless in most chemical processes.

To get a bit more technical, the number of protons within an atom’s nucleus is its ‘atomic number’ (aka the ‘proton number‘, usually notated ‘Z‘). Since protons are positively charged, each atom worth its salt will try to keep the same number of electrons in orbit to balance out its overall electric charge. If not, they’ll try to find other charge-impaired atoms and form ionic compounds, like literal salt, or covalent bonds — but that’s another story for another time.


Electron shells are made of several layers/orbitals. Although depicted round here, that’s only for simplicity’s sake. These orbitals can form very complicated shapes.
Image via Pixabay.

What’s important right now is to keep in mind that these atomic numbers identify individual elements. The atomic number is roughly equivalent to an element’s numeric place in the periodic table, and in broad lines dictates how an element tends to behave. All isotopes of an element have the same atomic number. What they differ in is their ‘mass number‘ (usually abbreviated ‘A‘), which denotes the total number of protons and neutrons in an atom’s core.

In other words, isotopes are atoms of the same element — but some just weigh more.

For example, two isotopes of Uranium, U-235 and U-238, have the same atomic number (92), but mass numbers of 235 and 238, respectively. You can have two isotopes of the same mass, like C-14 and N-14, that aren’t the same element at all, with atomic numbers 6 and 7, respectively. To find out how many neutrons an isotope harbors, subtract its atomic number from its mass number.

Do isotopes actually do anything?

For the most part, no. Generally speaking, there’s little to no difference in how various isotopes of the same element behave. This is partly a function of how we decide what each element ‘is’: roughly three-quarters of naturally-occurring elements are a mixture of isotopes. The average mass of a bunch of these isotopes put together is how we determine those elements’ standard atomic weights.

But, chiefly, it comes down to the point we’ve made previously: without differences in their electron shell, isotopes simply lack the means to change their chemical behavior. Which is just peachy for us. Taken together, the 81 stable elements known to us can boast some 275 stable isotopes. There are over 800 more radioactive (unstable) isotopes out there — some natural, and some we’ve created in the lab. Imagine the headache it would cause if they all behaved in a different way. Carbon itself has 3 stable isotopes — would we even exist today if each had its own quirks?

One element whose isotopes do differ meaningfully, however, is the runt of the periodic table: hydrogen. This exception is based on the atom’s particular nature. Hydrogen is the simplest chemical element, one proton orbited by one electron. Therefore, one extra neutron in the core can significantly alter the atom’s properties.

Hydrogen Isotopes.

Hydrogen’s isotopes are important enough for industrial and scientific applications that they received their own names.
Image credits BruceBlaus / Wikimedia.

For example, two of hydrogen’s natural isotopes, H-2 and H-3, have 1 and 2 neutrons respectively. Carbon (Z=6) has 2 stable isotopes: C-12 and C-13, with 6 and 7 neutrons respectively. In relative terms, there isn’t a huge difference in the neutrons’ share in their cores: they represent 50%, and 66.6% of the atoms’ weight in H-2, H-3, and 50% and 54-ish% of the total mass in C-12 and C-13. In absolute terms, though, the difference is immense: one neutron will double the mass of a hydrogen atom — two neutrons will triple it. For comparison, a single neutron is just 16.6% of a carbon atom’s mass.

While isotopes are highly similar chemically, they do differ physically. All that weight can alter how isotopes of light elements, hydrogen especially, behave. One example of such differences is the kinetic isotope effect — basically, heavier isotopes of the same element tend to be more sluggish during chemical reactions than lighter isotopes. For heavier elements, this effect is negligible.

Another quirky property of isotopes is that they tend to behave differently when exposed to infrared range than the ‘default’ elemental atoms. So, molecules that contain isotopes will look different to the same molecule sans isotopes when seen through an infrared camera. This, agian, is caused by their extra mass — the shape and masses of atoms in a molecule change how it vibrates, which in turn, changes how they interact with photons in the infrared range.

Where do isotopes come from?

Long story short, isotopes are simply atoms with more neutrons — they were either formed that way, enriched with neutrons sometime during their life, or are originated from nuclear processes that alter atomic nuclei. So, they form like all other atoms.

Lighter isotopes likely came together a bit after the Big Bang, while heavier ones were synthesized in the cores of stars. Isotopes can also form following the interaction between cosmic rays and energetic nuclei in the top layers of the atmosphere.

CNO cycle.

The carbon-nitrogen-oxygen (CNO) cycle, one of the two known sets of fusion reactions by which stars convert hydrogen to helium. P or ‘proton’ here is a positive hydrogen ion (aka hydrogen stripped of its electron).
Image credits Antonio Ciccolella / Wikimedia.

Isotopes can also be formed from other atoms or isotopes that have undergone changes over time. One example of such a process is radioactive decay: basically, unstable isotopes tend to shift towards a stable configuration over time. This can cause one unstable isotope to change into a stable one of the same element, or into isotopes of other elements with similar nucleic structures. U-238, for example, decays into Th-234.

This process, known as beta decay, occurs when there are too many protons compared to neutrons in a nucleus (or vice-versa), so one of them transforms into the other. In the example above, the uranium atom is the parent isotope, while the thorium atom is the daughter isotope. During this process, the nucleus emits radiation in the form of an electron and an antineutrino.

What are isotopes good for?

One of the prime uses for isotopes is dating (like carbon dating). One particular trait of unstable isotopes is that they decay into stable ones — but they always do so with the exact same speed. For example, C-14’s half-life (the amount of time needed for half of all isotopes in a sample to decay) is 5,730 years.

C-14 is formed in the atmosphere, and while an organism is alive, it ingests about one C-14 atom for every trillion stable C-12 isotopes through the food it eats. This keeps the C-12 to C-14 ratio roughly stable while it is alive. Once it dies, intake of C-14 stops — so by looking at how many C-14 atoms a sample has, we can calculate how far down C-14’s half-life it’s gone, meaning we can calculate its age.

At least, in theory. All our use of fossil fuels is pumping more C-14 isotopes into the atmosphere than normal, and it’s starting to mess up the accuracy of carbon dating.

To see how many C-14 atoms something has, we use accelerator mass spectrometry — a method that separates isotopes via mass.

PET (Positron-emission tomography) scans use the decay of so-called ‘medical isotopes‘ to peer inside the body. These isotopes are produced in nuclear reactors or accelerators called cyclotrons.

Finally, we sometimes create ‘enriched’ materials, such as enriched Uranium, to be used in nuclear reactors. This process basically involves us weeding through naturally-occurring uranium atoms via various methods for heavier isotopes, then separating those. The metal that we’ve already removed the heavier isotopes from (which are more unstable and thus more radioactive than ‘regular’ uranium) is known as ‘depleted uranium’.

Big atom schematic.

Researchers create gigantic atom filled with 100 other atoms

Like a bag of chips, atoms are mostly empty space. However, a highly exotic state of matter that was recently created by a team from the  Vienna University of Technology, the Harvard University, and Rice University, Texas, flips that notion on its head — dubbed a Rydberg polaron, this giant atom is filled with other atoms.

Big atom schematic.

The excided electron (blue) orbits its nucleus (red), and encloses other atoms of the Bose-Einstein-condensate (green).
Image credits TU Wien.

Atoms are made up of big bits, called protons and neutrons, that coalesce at its core to make the nucleus, and tiny bits named electrons, which orbit the core at great speeds. What holds them together is electromagnetics — the protons hold a positive charge, the electrons are negatively charged, so they attract one another. Neutrons don’t carry a charge so nobody much minds them.

Between the nucleus and the electrons, there’s a wide, thick helping of nothing. Literally. As far as we know, there is only empty space between the two, which means atoms are pretty much empty space. However, an international team of researchers wants to change that.

The biggest of the small

They started out from two different, and very extreme, fields of atomic physics: Bose-Einstein condensates and Rydberg atoms. A Bose-Einstein condensate is a state of matter created from ultracold bosons — close to absolute zero, or 0° Kelvin (which is -273.15° Celsius, or -459.67° Fahrenheit). That’s cold enough that quantum processes would find it hard to continue, meaning everything is more stable, denser, and certain aspects of quantum physics become observable. Rydberg atoms are also mostly empty space, but with a twist. One of their electrons is highly excited (to read: pumped full of energy) and orbits the nucleus at a very great distance:

“The average distance between the electron and its nucleus can be as large as several hundred nanometres – that is more than a thousand times the radius of a hydrogen atom,” said Professor Joachim Burgdörfer of Vienna University, co-author of the paper, in a statement.

The team put the two together by supercooling strontium and then using a laser to transfer energy to one atom and transform it into a Rydberg atom. Because the excited electron orbited at a much longer radius than in a typical atom, and because everything was clumped in so tightly, it ended up orbiting not just its nucleus, but as many as 170 other strontium atoms that were stuck between the two.

“The atoms do not carry any electric charge, therefore they only exert a minimal force on the electron,” said co-author Shuhei Yoshida.

Even these tiny tugs can steer the electron very slightly, however, without pushing it out of its orbit. This interaction consumes part of the total energy in the system, and that’s something chemistry likes and tries to perpetuate — so a bond forms between the Rydberg atom and those caught in its orbit.

“It is a highly unusual situation,” Yoshida explained. “Normally, we are dealing with charged nuclei, binding electrons around them. Here, we have an electron, binding neutral atoms.”

This exotic state of matter, dubbed a Ryberg polaron, is only stable while everything stays close to 0° K. If things get too heated, the particles start moving faster and the bond shatters.

“For us, this new, weakly bound state of matter is an exciting new possibility of investigating the physics of ultracold atoms,” said Burgdörfer. “That way one can probe the properties of a Bose-Einstein condensate on very small scales with very high precision.”

The paper “Creation of Rydberg Polarons in a Bose Gas” has been published in the journal Physical Review Letters.

Scientists win photo contest with image of a single, trapped atom

A mind-bending image of a single strontium atom, held near motionless by electric fields, has won the overall prize in a national science photography competition, organized by the Engineering and Physical Sciences Research Council (EPSRC). Here it is:

“In the center of the picture, a small bright dot is visible – a single positively-charged strontium atom. It is held nearly motionless by electric fields emanating from the metal electrodes surrounding it. […] When illuminated by a laser of the right blue-violet color, the atom absorbs and re-emits light particles sufficiently quickly for an ordinary camera to capture it in a long exposure photograph. [..] Laser-cooled atomic ions provide a pristine platform for exploring and harnessing the unique properties of quantum physics. They are used to construct extremely accurate clocks or, as in this research, as building blocks for future quantum computers, which could tackle problems that stymie even today’s largest supercomputers.”

The EPSRC content allows researchers and doctoral students to share another side of their work. It’s fitting that this year, it was won by an image of a single atom, as it shows just how much you can say through a single image.

David Nadlinger, says that the photo idea came as a way to bridge the invisible, microscopic world of the quantum world with our macroscopic, everyday life.

“The idea of being able to see a single atom with the naked eye had struck me as a wonderfully direct and visceral bridge between the miniscule quantum world and our macroscopic reality. A back-of-the-envelope calculation showed the numbers to be on my side, and when I set off to the lab with camera and tripods one quiet Sunday afternoon, I was rewarded with this particular picture of a small, pale blue dot.” What a beautiful homage to Carl Sagan!

Nadlinger’s wasn’t the only breathtaking image in the competition. Here are a few more stunning entries.

Photograph: Estelle Beguin/University of Oxford/EPSRC Photography Competition 2017.

Microbubbles are currently used to enhance the contrast of ultrasound diagnostic images. They are also explored as a way to deliver drugs to targeted areas such as tumors. Here, an electron microscopy image shows a micron-sized bubble coated with nano-sized liposomes containing the drug.

Photograph: Dr Mahetab Amer/University of Nottingham/EPSRC Photography Competition 2017.

High throughput screening is used to screen polymers and investigate their material properties, as well as their biocompatibility. This, in turn, enables researchers to understand how these polymers can turn human mesenchymal stem cells’ into bone cells. The attached cells show different morphologies on different polymer surfaces, shown here.

Photograph: Alastair Marsh/University of Bath/EPSRC Photography Competition 2017.

Just Mud, or the Future Sustainable Concrete by Alastair Marsh, University of Bath Soil, has potential as a next generation, low-carbon construction material, and could replace concrete blocks. But to unlock its potential, researchers must first understand how they can turn different clays into water-resistant, strong and durable materials.

You can see all the entries here.

We really are made of star stuff: half of the atoms inside us come from intergalactic space

Simulations reveal a poetic side to our inner atoms.

I guess we’re all intergalactic immigrants. Image credits: Spitzer / NASA.

A sense of scale

Even the size of the Earth can be hard to fathom. Nowadays, it can be so easy to get from place to place by driving or flying that our sense of distance gets distorted. But let’s translate things into something more familiar.

If you could magically walk on water, it would take 140 days of heavy walking to pass the almost 6,000 km from New York to London. You might think that’s incredibly far, but when it comes to outer space, that’s just peanuts. The Moon, our satellite, is 384.400 km away from the Earth. We got to the Moon in 1969, but to this day, we haven’t been able to plan a mission to Mars — which is much farther away. If you think that’s far, just consider how big the solar system is: the distance between the Sun and Neptune is 4.49 billion km. Then, let’s consider the next solar system, which is 4.22 light years away — a whopping 40,000 billion kilometers away from Earth. Are you getting the sense of scale? We’re not done yet.

There are an estimated 100 billion solar systems in our galaxy, with comparable distances between them. The immensity of the galaxy truly is humbling, and the distance between galaxies? That’s at over 11 million light years, and I just don’t want to put that in kilometers.

You might wonder why we did all that contorted imagination exercise. Well, we went from a very large but conceivable distance (New York to London) to an unfathomable distance outside our galaxy. Everything outside our galaxy is so far away that seems like it couldn’t possibly affect us. Except, as scientists learned, half of the matter in our own galaxy comes from outside.

Star stuff

Carl Sagan famously said we are made of star stuff, and his words ring truer today more than ever. According to modern physics, the first atomic nuclei were formed three minutes after the Big Bang — before that, things were just too hot for the atoms to be stable. This is the so-called nucleosynthesis era.

But at that time, only hydrogen, helium, and some trace quantities of lithium were formed, so where does all the other stuff come from? Well, things like carbon, oxygen, or heavier elements such as gold and silver, were formed in the primordial supernovae: incredibly huge and relatively short-lived stars. These supernovae exploded with such incredible power that they scattered matter all over the universe.

Faucher-Giguère and his co-author Daniel Anglés-Alcázar wanted to see to what extent is matter in the Milky Way a far traveler. They found that matter travel has been greatly underrated.

Galactic winds as a mode of transfer has been underappreciated,” says Jessica Werk at the University of Washington in Seattle. “Daniel Anglés-Alcázar uses one of the best simulations to do a detailed particle tracking analysis and really laid it all out for us.”

In a report in the Monthly Notices of the Royal Astronomical Society, they write that the Milky Way absorbs about one sun’s worth of extragalactic material every year, and that half of the matter inside the galaxy was actually “imported.” In a way, we’re all intergalactic travelers.

“The surprising thing is that galactic winds contribute significantly more material than we thought,” said Anglés-Alcázar. “In terms of research in galaxy evolution, we’re very excited about these results. It’s a new mode of galaxy growth we’ve not considered before.”

Aside from the romantic aspect, the study also offers an important scientific perspective. Knowing where matter comes from and how it evolves is one of the cornerstones of modern cosmology.

“It’s one of the holy grails of extra galactic cosmology,” Werk says. “Now, we’ve found that half these atoms come from outside our galaxy.”

Journal reference: Monthly Notices of the Royal Astronomical SocietyDOI: 10.1093/mnras/stx1517

Single-atom magnets used to create data storage one million times more dense than regular hard disks

A team of researchers has created the smallest and most efficient hard drive in existence using only two atoms. This technology is currently extremely limited in the amount of data it can store, but the technique could provide much better storage when scaled up.

Image credits Michael Schwarzenberger.

Hard drives store data as magnetic fields along a disk housed inside the drive. It’s split into tiny pieces and each acts like a bar magnet, with the field pointing either up or down (1 or 0) to store binary information. The smaller you can make these areas, the more data you can cram onto the disk — but you can’t make them too small, or you risk making them unstable so the 1’s and 0’s they store can and will switch around.

What if you used magnets that remained stable even when made to be really tiny? Well, those of you that remember physics 101 will know that cutting a magnet in two makes two smaller magnets. Cut them again in half and you get four, then eight and so on smaller magnets — but they also become less stable.

But a team of researchers has now created something which seems to defy all odds: stable magnets from single atoms. In a new paper, they describe how using these tiny things they created an atomic hard drive, with the same functionality as a traditional drive, but limited to 2 bits of data storage.

Current commercially-available technology allows for one bit of data to be stored in roughly one million atoms — although this number has been reduced to 1 in 12 in experimental settings. This single-atom approach allows for one bit of data to be stored in one single atom. A scaled-up version of this system will likely be less efficient, but could increase current storage density by a factor of 1,000, says Swiss Federal Institute of Technology (EPFL) physicist and first author Fabian Natterer.

Holmium bits

Looks hairy.
Image source Images of Elements / Wikipedia.

Natterer and his team used holmium atoms, a rare-earth metal, placed on a sheet of magnesium oxide and cooled to below 5 degrees Kelvin. Holmium was selected because it has many unpaired electrons (which creates a strong magnetic field) sitting in a close orbit to the atom’s nucleus (so they’re relatively well protected from outside factors). These two properties taken together give holmium a strong and stable magnetic field, Natter explains, but it also makes the element frustratingly difficult to interact with.


The team used a pulse of electric current released from the magnetized tip of scanning tunneling microscope to flip the atoms’ field orientation — essentially writing data into the atoms. Testing showed that these atomic magnets could retain their state for several hours, and showed no case of spontaneous flip. The same microscope was used to then read the bits stored in the atoms. To double-check that the data could be reliably read, the team also devised a second read-out method. By placing an iron atom close to the magnets and tuning it so that its electronic properties depended on the orientations of the 2-bit systems. This approach allowed the team to read out multiple bits at the same time, making for a faster and less invasive method than the microscope reading technique, Otte said.

It works, but the system is far from being practical. Two bits is an extremely low level of data storage compared to every other storage method. Natterer says that he and his colleagues are working on ways to make large arrays of single-atom magnets to scale-up the amount of data which can be encoded into the drives.

But the merits and possibilities of single-atom magnets shouldn’t be overlooked, either. In the future, Natterer plans to observe three mini-magnets that are oriented so their fields are in competition with each other, making each other continually flip.

“You can now play around with these single-atom magnets, using them like Legos, to build up magnetic structures from scratch,” he says.


Other physicists are sure to continue research into these magnets as well.

The full paper “Reading and writing single-atom magnets” has been published in the journal Nature.

A molecular knot with eight crossings. Credit: YouYube/University of Manchester.

Tightest molecular knot could lead to better, stronger materials

Researchers from the University of Manchester, the birthplace of graphene, have made their own molecular Gordian Knot. They used a strand of 192 atoms coiled around a triple loop which crosses itself eight times. It’s the most complex molecular knot ever created and might usher in a new class of super-strong materials.

A molecular knot with eight crossings. Credit: YouYube/University of Manchester.

A molecular knot with eight crossings. Credit: YouYube/University of Manchester.

Knotting and weaving were revolutionary for early humans. This technology brought us clothes, shelter, and new tools which dramatically improved life. David Leigh, a professor of chemistry at the University of Manchester and lead researcher of the new study says molecular knotting could potentially render returns in the same order of magnitude.

“Some polymers, such as spider silk, can be twice as strong as steel so braiding polymer strands may lead to new generations of light, super-strong and flexible materials for fabrication and construction,” Leigh said in a statement.

Molecular braiding

Leigh says tying a knot is similar to weaving, so molecular knots could pave the way for the weaving of molecular strands. Kevlar, the familiar and very tough material used in bullet-proof vests, is actually a plastic whose molecular rods are arrayed in a parallel structure. By interweaving molecular strands we should come up with even tougher, stronger materials. Molecular knots of ever increasing complexity represent baby steps in this direction.

Molecules tie themselves in knots naturally. There are six billion prime knots that we know of which, like prime numbers, can’t be broken down into simpler constituents. As such, you can’t make a new prime knot by stitching other prime knots together.

The first synthesized molecular knot looked like a three-leaf clover. Its configuration, known as a trefoil, was made in 1989 by a team led by eminent chemist Jean-Pierre Sauvage who would go on to win the Nobel Prize for chemistry in 2016 for earlier work that used the same principles. Since then, other small molecules have been arranged in prime knots but the process proved challenging.

In 2012, Leigh’s lab took things an order of magnitude farther after the researchers synthesized a type of molecular knot arranged in a star-shaped structure made up of 160 atoms whose strands crossed five times. Their latest knot has eight crossing points making it even more intricate, as reported in the journal Science.

Not as easy as tying your shoelace

To tie the knot, the molecular building blocks containing carbon, hydrogen, oxygen and nitrogen atoms, along with iron and chloride ions, are all mixed together. The chemical interactions between the atoms and the ions cause them to self-assemble. The metal ions hold the building blocks in the right position while a single chloride ion which sets at the center anchors the whole structure together. Finally, a chemical catalyst links all these building blocks to ‘tie’ the knot.

Right now it’s not clear yet how we can use this knots to make new materials but the potential is there. Leigh and other labs around the world are now faced with the challenge of synthesizing new knots of different configuration until someone makes a structure that proves practically useful.



In this artist's illustration, the NaK molecule is represented with frozen spheres of ice merged together: the smaller sphere on the left represents a sodium atom, and the larger sphere on the right is a potassium atom. Illustration: Jose-Luis Olivares/MIT

Scientists cool molecules just a hair over absolute zero (1,000,000 times colder than space)

In a breakthrough moment, researchers at MIT successfully cooled sodium potassium gas molecules (NaK) near absolute zero. At this temperature, matter behaves significantly different and starts exhibiting quantum effects. This is the coldest any molecule has been measured so far.

In this artist's illustration, the NaK molecule is represented with frozen spheres of ice merged together: the smaller sphere on the left represents a sodium atom, and the larger sphere on the right is a potassium atom.  Illustration: Jose-Luis Olivares/MIT

In this artist’s illustration, the NaK molecule is represented with frozen spheres of ice merged together: the smaller sphere on the left represents a sodium atom, and the larger sphere on the right is a potassium atom.
Illustration: Jose-Luis Olivares/MIT

Normally, at ambient temperature, molecules zip by at colossal speeds, colliding and reacting with each other. There probably are millions of such collisions happening every moment in the air you breath. When matter gets really cold though, its movements near to a halt as it’s chilled closer and closer to absolute zero (0 Kelvin or -273.15 degrees Celsius). Other strange things start happening as well. For instance, when Helium is cooled down to near zero the substance (a gas at room temperature) turns into a liquid with no viscosity – a superfluid. But it’s a lot easier to cool single atoms, like He, than molecules, which comprise two or more atoms linked by electromagnetic forces.

Molecules are a lot more complicated since they exhibit more complex degrees of freedom:  translation, vibration, and rotation. So, cooling the molecules directly is challenging, if not impossible with current means. To cool the sodium potassium gas, the researchers had to employ multiple steps. First, the MIT team used lasers and evaporative cooling to cool clouds of individual sodium and potassium atoms to near absolute zero. Typically, sodium and potassium don’t form compounds because they repel each other. However, the researchers “glued” them together by prompting the atoms to bond with an electromagnetic field. This mechanism is known as “Feshbach resonance.”

The resulting bond, however, is very weak – a “fluffy molecule”, as the researchers call it. To bring the atoms closer together, and strengthen the bond as a consequence, the researchers employed a novel technique used previously  in 2008 by groups from the University of Colorado, for potassium rubidium (KRb) molecules, and the University of Innsbruck, for non-polar cesium­ (Ce) molecules. Yet again, the weak molecules were exposed to a pair of laser pulses, the large frequency difference of which exactly matched the energy difference between the molecule’s initial, highly vibrating state, and its lowest possible vibrational state. The sodium potassium molecule absorbed the lower energy from one laser and emitted energy to the higher-frequency laser. So, what the MIT researchers got at the end were very low energy state, ultra-cold molecules sitting as low as 500 nanoKelvins or just billionths of a degree above absolute zero.

The resulting ultra-cool molecules were quite stable, with a relatively long lifetime, lasting about 2.5 seconds. The molecules also exhibited very strong dipole moments — strong imbalances in electric charge within molecules that mediate magnet-like forces between molecules over large distances. Concerning their speed, at such a cool temperature, the molecules average speeds of centimeters per second and are almost at their absolute lowest vibrational and rotational states.

“In the case where molecules are chemically reactive, one simply doesn’t have time to study them in bulk samples: They decay away before they can be cooled further to observe interesting states,” says Martin Zwierlein, professor of physics at MIT and a principal investigator in MIT’s Research Laboratory of Electronics. “In our case, we hope our lifetime is long enough to see these novel states of matter.”

The next step is cooling the molecule even further to maybe catch a glimpse of the quantum mechanical effects that are predicted should happen.  Findings appeared in the journal Physical Review Letters.

“We are very close to the temperature at which quantum mechanics plays a big role in the motion of molecules,” Zwierlein says. “So these molecules would no longer run around like billiard balls, but move as quantum mechanical matter waves. And with ultracold molecules, you can get a huge variety of different states of matter, like superfluid crystals, which are crystalline, yet feel no friction, which is totally bizarre. This has not been observed so far, but predicted. We might not be far from seeing these effects, so we’re all excited.”

edit: missed a very important “minus” sign for the absolute zero temperature value in Celsius (-273.15 degrees Celsius)

A cloud of ultracold atoms (red) is used to cool the mechanical vibrations of a millimeter-sized membrane (brown, in black frame). The mechanical interaction between atoms and membrane is generated by a laser beam and an optical resonator (blue mirror). Credit: Tobias Kampschulte, University of Basel

Coldest atom cloud in the world chills other matter close to absolute zero

For the first time, researchers at the University of Basel used an ultracool atomic gas to cool a very thin membrane to less than one degree Kelvin. The new technique might enable novel investigations of quantum mechanics phenomena and precision measuring devices.

Coldest matter in the world lends its freeze

A cloud of ultracold atoms (red) is used to cool the mechanical vibrations of a millimeter-sized membrane (brown, in black frame). The mechanical interaction between atoms and membrane is generated by a laser beam and an optical resonator (blue mirror). Credit: Tobias Kampschulte, University of Basel

A cloud of ultracold atoms (red) is used to cool the mechanical vibrations of a millimeter-sized membrane (brown, in black frame). The mechanical interaction between atoms and membrane is generated by a laser beam and an optical resonator (blue mirror). Credit: Tobias Kampschulte, University of Basel

In the ultracold world, produced by methods of laser cooling and trapping, atoms move at a snail’s pace and behave like matter waves. Typically, lasers are used to trap atoms inside a vacuum chamber, almost grounding all atomic vibrations to a halt and thus lower temperature close to less than 1 millionth of a degree above absolute zero. In this state, atoms behave differently – governed by laws of spooky quantum mechanics – and move in small wave packets. This means superposition or being in several places at once.

Ultracooled atoms are usually used in so called atomic clocks that only lose a second every couple hundred millions of years. These are very useful for syncing GPS satellites, for instance, but can ultracool atoms be used to refrigerate some other matter? It’s a very interesting idea, but only if one can surpass the challenges. Even the largest ultracool atom clouds, which can number billions of particles, aren’t larger than a grain of sand. Because the surface area is so small, it’s very difficult to transfer heat and cool objects.

There are workarounds, however. Swiss researchers successfully cooled the vibrations of a millimeter-sized membrane using ultracool atoms. The membrane, a silicon nitride film of 50 nm thickness, oscillates up and down like a small square drumhead. Such mechanical oscillators are never fully at rest but show thermal vibrations that depend on their temperature. Although the membrane contains about a billion times more particles than the atomic cloud, a strong cooling effect was observed, which cooled the membrane vibrations to less than 1 degree above absolute zero, as reported in Nature Nanotechnology.

“The trick here is to concentrate the entire cooling power of the atoms on the desired vibrational mode of the membrane,” explains Dr. Andreas Jöckel, a member of the project team.

A laser light was shone which changed the vibration of the membrane and transmitted the cooling effect over a distance of several meters. The effect was amplified by an optical resonator made of two mirrors, with the membrane sandwiched in between. Previously, systems that use light to couple ultracold atoms and mechanical oscillator had been proposed theoretically, but this is the first time it’s been demonstrated experimentally.

The take away is that such a system might be employed to experience quantum mechanical system in macrosized objects – the kind that you can see with the naked eye.

It may also be possible to generate what are known as entangled states between atoms and membrane. A membrane’s vibrations could be measured with unprecedented detail, and along with the improvement would follow a new class of highly sensitive sensors for small forces and masses.

“The well-controlled quantum nature of the atoms combined with the light-induced interaction is opening up new possibilities for quantum control of the membrane,” says Treutlein.



On the right, an artificial atom generates sound waves consisting of ripples on the surface of a solid. The sound, known as a surface acoustic wave (SAW) is picked up on the left by a "microphone" composed of interlaced metal fingers. According to theory, the sound consists of a stream of quantum particles, the weakest whisper physically possible. The illustration is not to scale. Image: Philip Krantz, Krantz NanoArt.

Researchers capture sound from atoms, opening new doors to quantum research

On the right, an artificial atom generates sound waves consisting of ripples on the surface of a solid. The sound, known as a surface acoustic wave (SAW) is picked up on the left by a "microphone" composed of interlaced metal fingers. According to theory, the sound consists of a stream of quantum particles, the weakest whisper physically possible. The illustration is not to scale. Image: Philip Krantz, Krantz NanoArt.

On the right, an artificial atom generates sound waves consisting of ripples on the surface of a solid. The sound, known as a surface acoustic wave (SAW) is picked up on the left by a “microphone” composed of interlaced metal fingers. According to theory, the sound consists of a stream of quantum particles, the weakest whisper physically possible. The illustration is not to scale. Image: Philip Krantz, Krantz NanoArt.

Most quantum research is focused on studying interactions between light and atoms, a field known as quantum optics. Researchers at Chalmers University of Technology in Sweden took an alternate route and demonstrated for the first time that acoustic waves could be used to communicate with an atom. The findings could provide an important stepping stone for harnessing quantum effects in the ‘real’, macro world with potential applications in quantum computing and more.

“We have opened a new door into the quantum world by talking and listening to atoms”, said Per Delsing, head of the experimental research group, in a press release. “Our long term goal is to harness quantum physics so that we can benefit from its laws, for example in extremely fast computers. We do this by making electrical circuits which obey quantum laws, that we can control and study.”

The sound of an atom

The quantum electrical circuit that the Swedish scientists built essentially acts like an artificial atom – it can become charged with electricity and release particles, just like a regular atom, as described in the journal Science. While other projects have successfully demonstrated artificial atoms that release photons (particles of light), this is the first time that such a quantum system was shown to emit and absorb energy in the form of sound particles.

Microscope image: This is a zoom-in of the artificial atom, with its integrated Superconducting Quantum Interference Device (SQUID) in violet. The SQUID gives the atom its quantum properties, and the fingers sticking up to the left provide the coupling to sound waves.

Microscope image: This is a zoom-in of the artificial atom, with its integrated Superconducting Quantum Interference Device (SQUID) in violet. The SQUID gives the atom its quantum properties, and the fingers sticking up to the left provide the coupling to sound waves. Image: Martin Gustafsson and Maria Ekström

The device they employed is made of a substrate of gallium arsenide (GaAs) and contains two vital components: a superconducting circuit that constitutes the artificial atom and an interdigital transducer (IDT), which converts electrical microwaves to sound and vice versa. The sound waves used in the experiment were surface acoustic waves (SAWs), which can be visualised on the surface of a solid, while the whole demonstration was performed at very low temperatures, near absolute zero (20 millikelvin), so that energy in the form of heat does not disturb the atom. The low temperature is also essential to make materials exhibit superconductive properties.  Superconducting materials can conduct electricity with no resistance, which means that they can carry a current indefinitely without losing any energy. Such materials are considered to be part of the new suit of electrical technology set to change the world in the future – that if scientists can find a way to make them work at near room temperature without them losing their properties.

Because the particular sound waves used in the experiment travel a lot slower than light (100,000 times slower), scientists can better control the quantum phenomena involved. This is because an atom that interacts with light waves is always much smaller than the wavelength. However, compared to the wavelength of sound, the atom can be much larger, hence it can be controlled easier.

: Heat map showing the production of exotic isotopes at the RIKEN Radioactive Isotope Beam Factory (RIBF). This facility can produce nickel-78 (78Ni) in yields sufficient for highly precise decay measurements. Credit: The American Physical Society

Nickel-78: a ‘doubly magic’ isotope

Some atoms are more stable than others, and the same goes for their isotopes – elements that have the same number of protons in the nucleus, but different number of neutrons. For instance, some decay in a trillionth of a second, while others can live on for billions of years. Actually, using isotopes (thorium and uranium decay) scientists were able to refine the dating for our planet’s age. The Earth is 4.54 billion years old.

The most exceptional isotopes are those that contain a ‘magic number’, as defined by scientists.The seven most widely recognized magic numbers are 2, 8, 20, 28, 50, 82 and 126, corresponding to the total number of protons and neutrons needed to completely fill the nuclear shells. Nickel-78 is perhaps the oddest of isotopes, and has been giving physicists headaches for ages because it is a ‘doubly magic’ isotope.

The nickel-78 (78-Ni) isotope contains 28 protons and 50 neutrons, making it doubly magic according to this series, but isotopes that exhibit such an excess of neutrons over protons are predicted to have a different magic number, according to models. This has prompted some scientists to say Nickel-78 isn’t magic at all.

: Heat map showing the production of exotic isotopes at the RIKEN Radioactive Isotope Beam Factory (RIBF). This facility can produce nickel-78 (78Ni) in yields sufficient for highly precise decay measurements. Credit: The American Physical Society

: Heat map showing the production of exotic isotopes at the RIKEN Radioactive Isotope Beam Factory (RIBF). This facility can produce nickel-78 (78Ni) in yields sufficient for highly precise decay measurements. Credit: The American Physical Society

Helping put an end to the debate are Shunji Nishimura and colleagues from the RIKEN Nishina Center for Accelerator-Based Science who have performed extensive experiments on Nickel-78.

“Many experiments have been carried out to identify systematic trends in nuclear properties near 78Ni,” says Nishimura. “Yet there has been no clear evidence on whether 78Ni is a double-magic nuclei due to the extremely low production yield of this isotope.”

The team used RIKEN’s Radioactive Isotope Beam Factory, which is capable of generating high yields of exotic and rare isotopes like 78Ni, as show in the figure above. Using this facility, in combination with the newly developed WAS3ABi detector, the research team was able to perform measurements of 78Ni decay with unprecedented precision. The experiments confirmed the doubly magic status of 78Ni, providing valuable insights into the behavior of exotic nuclei with large neutron excess. Such neutron-rich nuclei play an important role in the production of elements heavier than the most stable element iron, such as gold and uranium.

“We hope to solve one of the biggest mysteries of this century—where and how were the  created in the Universe?” explains Nishimura.

Findings were detailed in a paper published in the journal Physical Review Letters.

20 bromine atoms positioned on a sodium chloride surface using the tip of an atomic force microscope at room temperature, creating a Swiss cross with the size of 5.6nm. The structure is stable at room temperature and was achieved by exchanging chlorine with bromine atoms. Photo: Department of Physics, University of Basel

Smallest Swiss cross made of only 20 atoms demonstrates atom manipulation at room temp

Some applications require such a degree of precision that everything needs to be in exact order at the atom-scale. In an awesome feat of atomic manipulation,  physicists from the University of Basel,  in cooperation with team from Japan and Finland, have placed 20 atoms atop an insulated surface in the shape of a Swiss cross. Such experiments have been achieved with success before, but the real highlight is that this is the first time anything like this was made at room temperature.

20 bromine atoms positioned on a sodium chloride surface using the tip of an atomic force microscope at room temperature, creating a Swiss cross with the size of 5.6nm. The structure is stable at room temperature and was achieved by exchanging chlorine with bromine atoms. Photo: Department of Physics, University of Basel

20 bromine atoms positioned on a sodium chloride surface using the tip of an atomic force microscope at room temperature, creating a Swiss cross with the size of 5.6nm. The structure is stable at room temperature and was achieved by exchanging chlorine with bromine atoms. Photo: Department of Physics, University of Basel

Since the 1990s, scientists have been able to manipulate surface structures by individually moving and positioning atoms. This sort of demonstrations, however, were made mainly atop conducting or semi-conducting surfaces and only under very low temperatures. Fabricating artificial structures on fully insulated surfaces and at room temperature has always proven to be a challenge, but the international effort proved it is possible.

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The team led by Shigeki Kawai and Ernst Meyer from the Department of Physics at the University of Basel used an atomic force microscope to place single bromine atoms on a sodium chloride surface. Upon reacting with the surface, the bromine atoms would exchange position with chloride and the researchers carefully repeated each step until they formed a lovely Swiss cross made up of 20 such atoms. It’s so small that the surface area measures only a whooping 5.6 nanometers square. Effectively, the demonstration represents  the largest number of atomic manipulations ever achieved at room temperature.

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By proving atomic manipulation at this scale is achievable under room temperature, the scientists help pave the way for the next generation of electromechanical systems, advanced atomic-scale data storage devices and logic circuits that will most likely use a scaled version of their process.

The paper appeared in the journal Nature Communications.

Scientists inspecting the compressor of the Vulcan Petawatt laser.

High power laser hallows atom from the inside out

An international team of physicists have used one of the world’s most powerful lasers to create an unusual kind of plasma made out of hollow atoms, by using a breakthrough technique which involved emptying atoms of electrons from the inside out, instead of working from the outer shells inwards.  This bizarre physics experiment shows once again just how important X-rays are in physics interaction and deepens our understanding of fusion.

Scientists inspecting the compressor of the Vulcan Petawatt laser.

Scientists inspecting the compressor of the Vulcan Petawatt laser.

A hallow atom is created when electrons nested deep inside the atom are removed, typically by colliding the said electrons with other electrons, creating a “hole” inside the atom, while leaving the other electrons in place. Through this process, a distinct form of plasma is formed, and if the hole is filled X-rays are released. Plasma is a form of ionized gas, which mainly differentiates itself through its highly conductive electrical properties. In nature, a great example of plasma at work is lightning. Neon lights also make for a familiar display of plasma since its the latter which produces the light.

For their experiment, the researchers used the petawatt laser at the Central Laser Facility at the Science and Technology Facilities Council (STFC) Rutherford Appleton Laboratory to zap individual atoms. For context, the  petawatt laser delivers approximately 10,000 times the entire UK national grid, all in one zap lasting a thousand-billionth of a second, onto an area smaller than the end of a human hair. Impressed yet?

“At such extraordinary intensities electrons move at close to the speed of light and as they move they create perhaps the most intense X-rays ever observed on Earth. These X-rays empty the atoms from the inside out; a most extraordinary observation and one that suggests the physics of these interactions is likely to change, as lasers become more powerful,” said Dr Nigel Woolsey, from the York Plasma Institute, Department of Physics, at the University of York was the Principal Investigator for the experimental work.

A hallow atom from the inside out

So, unlike previous attempts to create hallow atoms, the current work doesn’t rely on electron or photon collision to create atom holes, instead it uses the resulting radiation field from the interaction to achieve the same effect; only from the inside out.

“This experiment has demonstrated a situation where X-ray radiation dominates the atomic physics in a laser-plasma interaction; this indicates the importance of X-ray radiation generation in our physics description. Future experiments are likely to show yet more dramatic effects which will have substantial implications for diverse fields such as laboratory-based astrophysics,” said Co-author Dr Alexei Zhidkov, from Osaka University.

The experiments provides further insight into fusion research, which offers the potential for  for an effectively limitless supply of safe, environmentally friendly energy.

Co-author Dr Sergey Pikuz, from the Joint Institute for High Temperatures RAS, said: “The measurements, simulations, and developing physics picture are consistent with a scenario in which high-intensity laser technology can be used to generate extremely intense X-ray fields. This demonstrates the potential to study properties of matter under the impact of intense X-ray radiation.”

Co-author Rachel Dance, a University of York PhD physics student, said: “This was a very dynamic experiment which led to an unexpected outcome and new physics.  The hollow atom diagnostic was set to measure the hot electron beam current generated by the laser, and the results that came out of this in the end, showed us that the mechanism for hollow atom generation, was not collisional or driven by the laser photons, but by the resulting radiation field from the interaction.”

Findings were reported in the journal Physical Review Letters.

Scientists split an atom in two and then fuse it back together

Atom = at·om, noun \ˈa-təm\, from the greek  ἄτομος (atomos) meaning “indivisible”.

Apparently the atom isn’t that indivisible after all. Scientists at University of Bonn have managed to split an atom into two with a special laser, in special conditions, before merging it back together. Just like in the case of light, quantum mechanics allowed an atom to be split and then fused back.

But how is this possible? In quantum mechanics, matter, say an atom, can exist in several different states at once – this formed the absolute basis of the so called “double-slit” experiment for the researchers. For their experiment the scientists successfully manged to keep a single atom in two place at once more than 10 microns apart from one another, an astronomical distance at the atomic scale.

This occurred only because the researchers imposed the right, necessary conditions for the quantum effect to take place. A cesium atom was cooled very close to absolute zero temperature using lasers, and was then moved with the help of another laser. The lasers were absolutely critical to the experiment, being employed to correct the atom’s spin. An atom can spin in both direction – clockwise or counterclockwise; for their current work, the researchers made the atom spin in both directions at the same time.

“The atom has kind of a split personality, half of it is to the right, and half to the left, and yet, it is still whole,” explained Andreas Steffen, the publication’s lead author.

If imaged, the atom sometimes shows on the left, the right, or in the center, but the split can be proved by putting the atom back together

“Thus an interferometer can be built from individual atoms that can, e.g., be used to measure external impacts precisely. Here, the atoms are split, moved apart and joined again. What will become visible, e.g., are differences between the magnetic fields of the two positions or accelerations since they become imprinted in the quantum mechanical state of the atom. This principle has already been used to very precisely survey forces such as Earth’s acceleration.”

Of course, this wasn’t all for show and tell. The researchers hope to better learn not only how to control individual atoms, but how multiple atoms  are linked together using quantum mechanics. This insight can be then used to develop quantum systems, to simulate intricate phenomena, like photosynthesis, which can’t be simulated by today’s supercomputers.

“For us, an atom is a well-controlled and oiled cog,” said Dr. Andrea Alberti, the team lead for the Bonn experiment. “You can build a calculator with remarkable performance using these cogs, but in order for it to work, they have to engage.”

“This is where the actual significance of splitting atoms lies: Because the two halves are put back together again, they can make contact with adjacent atoms to their left and right and then share it. This allows a small network of atoms to form that can be used — like in the memory of a computer — to simulate and control real systems, which would make their secrets more accessible.”

The findings were published in the journal Proceedings of the National Academy of Sciences.

Source: University of Bonn via Planetsave

Captured: first ever images of atom moving inside a molecule

A Romanian scientist working at the University of Ohio captured the first-ever images of atoms moving within a molecule by applying a novel technique which basically turns the electrons of a molecule into flashbulbs; while this is currently only a new way to visualize molecules, researchers believe that one day it will be the key to controlling chemical reactions at an atomic scale.

The photos were taken using a hi-tech laser, which fired 50 femtosecond pulses at the molecule, in a successful attempt to knock down electrons outside the outer shell; the strayed electron then comes crashing down to the molecule, and in doing so provides the kind of illumination scientists need to illuminate the setting. A femtosecond is a quadrillionth of a second.

By measuring the scattered signal of the knocked out electron as it collides with the molecule, they were able to reconstruct the molecule’s elements, including the positions of the atom nuclei. What’s just as spectacular is that due to a short lag between when the electron is knocked out and when it crashed into the molecule, researchers were able to capture the atom’s movement during that short period – practically creating a frame-by-frame motion picture of the nuclei and electrons.

For their experiments they used simple, oxygen (O2) and nitrogen (N2) molecules, especially because their molecular structures are so well understood. The next steps involve using more and more complex atoms, eventually improving what we know of the molecular structure from these studies, and ultimately being able to control chemical reactions at an atomic level

Atom nuclei can store information

In case you’re wondering, what you’re looking at is a silicon chip, only 1 millimeter square that was used by researchers to prove how data can be stored in the magnetic spin of atoms – and how it can then be accessed electronically. Physicists from the University of Utah have managed to store information in the magnetic spin of a phosphorus atom, which is a major step in developing new types of memory for both traditional and quantum computers.

“The length of spin memory we observed is more than adequate to create memories for computers,” says Christoph Boehme (pronounced Boo-meh), an associate professor of physics and senior author of the new study, published Friday, Dec. 17 in the journal Science. “It’s a completely new way of storing and reading information.”

The technical difficulties they had to face were huge; the apparatus they used only works at 3.2 Kelvin grades, which is just slightly above absolute zero – the temperature at which all atoms reach a standstill ! Also, it had to be surrounded by an electric field roughly 200.000 greater than that of the Earth.

“Yes, you could immediately build a memory chip this way, but do you want a computer that has to be operated at 454 degrees below zero Fahrenheit and in a big national magnetic laboratory environment?” Boehme says. “First we want to learn how to do it at higher temperatures, which are more practical for a device, and without these strong magnetic fields to align the spins.”
As for obtaining an electrical readout of data held within atomic nuclei, “nobody has done this before,” he adds.

Large Hadron Collider creates mini big bangs and incredible heat

The Large Hadron Collider at CERN has taken another step towards its goal of finding the so called ‘god particle‘: it recently produced the highest temperatures ever obtained through a science experiment. The day before yesterday, 7 November was a big one at the LHC, as the particle collider started smashing lead ions head-on instead of the proton – proton collisions that usually take place there.

Representation of a quark-gluon plasma

The result was a series of what is called mini big bangs: dense fireballs with temperatures of over 10 trillion Celsius degrees! At this kind of temperatures and energies, the nuclei of atoms start to melt in their constituend parts, quarks and gluons, and the result is called a quark-gluon plasma.

One of the primary goals of the Large Hadron Collider is to go back further and further in time, closer to the ‘birth’ of the Universe. The theory of quantum chromodynamics tells us that as we ‘travel’ in the past more and more, the strength of strong interactions drops fast and reaches zero; the process is called “asymptotic freedom”, and it brought David Politzer, Frank Wilczek and David Gross a Nobel Prize in 2004.

The quark-gluon plasma has been studied in great detail at the Relativistic Heavy Ion Collider (RHIC) at Upton, New York, which produced temperatures of 4 trillion degrees Celsius. These collisions will allow scientists to look at the world in a way they never could have before, showing how the Universe was about a millionth of a second after the big bang. One can only wonder what answers this plasma has to offer, and it already produced a huge surprise, acting like a perfect liquid instead of a gas, as expected. Still, one thing’s for sure: the Large Hadron Collider is producing more and more results each month, and whether it confirms current theories or proves them wrong, science will benefit greatly from this particle collider

LHC produces first results

Since the Large Hadron Collider went back in business, all sort of rumors have been circling the scientific circles (and not only). However, until these rumors are proven wrong or right, the first official paper on proton collisions from the Large Hadron Collider has been published in this week’s edition of Springer’s European Physical Journal C. .


Designed to reach the highest energy ever explored in particle accelerators, it features a circular tunnel with the circumference of 27 km. Since it’s been recommissioned, a total of 284 collisions have been recorded, all of which have been analyzed and interpreted. The researchers have been able to determine what is called ‘pseudorapidity density’ (the average number of charged particles that are emitted perpendicular to the beam direction. The goal of this was to compare the results with those obtained in the case of proton-antiproton collisions that took place in the same conditions.

The paper was published by ALICE (a Large Ion Collider Experiment that brings together authors from 113 institutions). As well as the actual results, the paper also explains how their detecting and analyzing system works. The results are not only consistent with earlier measurements, but they also fit the theoretical model produced by researchers.

Dr. Jürgen Schukraft from CERN and ALICE spokesperson said: “This important benchmark test illustrates the excellent functioning and rapid progress of the LHC accelerator, and of both the hardware and software of the ALICE experiment, in this early start-up phase. LHC and its experiments have finally entered the phase of physics exploitation.”