Tag Archives: atoms

Scientists image atoms with record resolution close to absolute physical limits

An electron ptychographic reconstruction of a praseodymium orthoscandate (PrScO3) crystal, zoomed in 100 million times. Credit: Cornell University.

Physicists at Cornell University have pushed the boundaries of atomic imaging by pushing the resolution of an electron microscope by a factor of two. While many modern smartphones have high-resolution cameras that allow you to zoom in a lot, they’re no match for this setup that can reconstruct ultraprecise images with one-trillionth of a meter precision. You can see individual atoms and the chemical bonds in molecules.

The researchers, led by Professor David Muller, devised an electron microscope pixel array detector and state-of-the-art 3D reconstruction algorithms to take laser-precise images of atoms. The resolution is so sharp that the only blurred element is the thermal jiggling of the atoms themselves.

“This doesn’t just set a new record,” Muller said. “It’s reached a regime which is effectively going to be an ultimate limit for resolution. We basically can now figure out where the atoms are in a very easy way. This opens up a whole lot of new measurement possibilities of things we’ve wanted to do for a very long time,” Muller said.

The breakthrough hinges on a computer-algorithm-driven technique known as ptychography, which works by scanning overlapping scattering patterns from a sample and then looking for changes in the overlapping region.

“We’re chasing speckle patterns that look a lot like those laser-pointer patterns that cats are equally fascinated by,” Muller said. “By seeing how the pattern changes, we are able to compute the shape of the object that caused the pattern.”

The detector used by the electron microscope is very slightly defocused on purpose. This way the blurred beam can capture the widest range of data possible. The data is then used to reconstruct a sharp image of the sample via complex algorithms.

“With these new algorithms, we’re now able to correct for all the blurring of our microscope to the point that the largest blurring factor we have left is the fact that the atoms themselves are wobbling, because that’s what happens to atoms at finite temperature,” Muller said. “When we talk about temperature, what we’re actually measuring is the average speed of how much the atoms are jiggling.”

Due to the jiggling of the atoms, the researchers claim that their achievement is almost at the physical lower bound of atomic imaging. Theoretically, they could break their own record and achieve an even higher resolution by freezing the sample close to absolute zero temperature. However, even at close to zero, there are still quantum fluctuations and the improvements would only be marginal at best anyway. 

Electron ptychography will allow scientists to identify individual atoms in 3-D space that may be obscured by other imaging methods. Immediate applications include detecting impurities in samples, as well as imaging them and their vibrations. For the industry, this is particularly useful when assessing the quality of semiconductors, catalysts, and sensitive quantum materials meant for quantum computers.

“We want to apply this to everything we do,” said Muller.”Until now, we’ve all been wearing really bad glasses. And now we actually have a really good pair. Why wouldn’t you want to take off the old glasses, put on the new ones, and use them all the time?”

The findings appeared in the journal Science.

This article originally appeared in May 2021.

What Can Quartz Crystals Really Do?

Image in public domain.

Crystals and quartz

Crystals have caught the eye of humans since the dawn of time. Some scientists have even speculated that the origins of life on Earth may trace its origins to crystals. It shouldn’t come as a surprise that these gleaming mineral formations appear frequently in pop culture often as having supernatural powers (even though they don’t). A few examples of this reoccurring theme are the Silmarils in the Lord of the Rings universe and the sunstones in James Gurney’s Dinotopia.

The atoms which make up a crystal lie in a lattice which repeats itself over and over. There are several methods for generating crystals artificially in a lab, with superheating being the most common process. Likewise, in nature, a hot liquid (eg: magma) cools down, and as this happens, the molecules are attracted to each other, bunching up and forming that repeating pattern which leads to crystal formation.

Quartz is one of the most abundant minerals found on the planet. This mineral is known to be transparent or have the hues of white, yellow, pink, green, blue, or even black. It is also the most common form of crystalline silica which has a rather high melting point and can be extremely dangerous if inhaled in its powdered form. This mineral compound is present in the majority of igneous rocks. Some quartzes are considered semiprecious stones. Aside from mere bedazzlement, they have been used in countless industries.

Industrial, not magical uses

If a pressure is applied to the surface of a quartz crystal, it can give off a small electrical charge. This effect is the result of the electrically charged atoms (the ions) dispersing and spreading away from the area to which the pressure is being applied. This can be done in a number of ways, including simply squeezing the crystal. It also dispenses an electric current if a precise cut is made at an angle to the axis.

Since it possesses this property, quartz has been a component of devices such as radios, TV’s, and radar systems. Some quartz crystals are capable of transmitting ultraviolet light better than glass (by the way, quartz sand is used in making glass). Because of this, low-quality quartz is often used for making specific lenses; optical quartz is made exclusively from quartz crystals. Quartz which is somewhat clouded or which is not as transparent as the stuff used for optics is frequently incorporated into lab instrumentation.

Scientists have employed quartz for many things, and they have considered its role in the Earth sciences a crucial one. Some have stated it directly brings about the reaction which forms mountains and causes earthquakes! It continues to be used in association with modern technology, and it likely will lead us to more discoveries in the future.

fusion vs fission

What’s the difference between nuclear fission and fusion

fusion vs fission

Fission vs fusion reaction. Credit: Duke Energy.

In both fusion and fission, nuclear processes alter atoms to generate energy. Despite having some things in common, the two can be considered polar opposites.

For the sake of simplicity, nuclear fusion is the combination of two lighter atoms into a heavier one. Nuclear fission is the exact opposite process whereby a heavier atom is split into two lighter ones.

Fission vs fusion at a glance

Nuclear Fission Nuclear Fusion
  • A heavy nucleus breaks up to form two lighter ones.
  • It involves a chain reaction, which can lead to dangerous meltdowns.
  • The heavy nucleus is bombarded with neutrons.
  • There is established, decades-old technology to control fission.
  • Nuclear waste, a byproduct of fission, is an environmental challenge.
  • Raw material like plutonium or uranium is scarce and costly.
  • Two nuclei combine to form a heavier nucleus.
  • There is no chain reaction involved.
  • Light nuclei have to be heated to extremely high temperature.
  • Scientists are still working on a controlled fusion reactor that offers more energy than it consumes.
  • There is no nuclear waste.
  • Raw materials are very easily sourced.
  • Fusion reactions have energy densities many times greater than nuclear fission.

From Einstein to nuclear weapons

On November 21, 1905, physicist Albert Einstein published a paper in Annalen der Physik calledDoes the Inertia of a Body Depend Upon Its Energy Content? This was one of Einstein’s four Annus Mirabilis papers (from Latin, annus mīrābilis, “Extraordinary Year”) in which he described what has become the most famous physical equation:  E = mc2 (energy equals mass times the velocity of light squared).

This deceivingly simple equation can be found everywhere, even in pop culture. It’s printed on coffee mugs and T-shirts. It’s been featured in countless novels and movies. Millions of people recognize it and can write it down by heart even though they might not understand anything about the physics involved.

Before Einstein, mass was considered a mere material property that described how much resistance the object opposes to movement. For Einstein, however, relativistic mass — which now takes into account the fact that mass increases with speed — and energy are simply two different names for one and the same physical quantity. We now had a new way to measure a system’s total energy simply by looking at mass, which is a super-concentrated form of energy.

It didn’t take scientists too long to realize there was a massive amount of energy waiting to be exploited. By the process through which fission splits uranium atoms, for instance, a huge amount of energy, along with neutrons, is released. Interestingly, when you count all the particles before and after the process, you’ll find the total mass of the latter is slightly smaller than the former. This difference is called the ‘mass defect’ and it’s precisely this missing matter that’s been converted into energy, the exact amount computable using Einstein’s famous equation. This mass discrepancy might be tiny but once you multiply it by c2 (the speed of light squared), the equivalent energy can be huge.

Of course, this conservation of energy holds true across all domains, both in relativistic and classical physics. A common example is spontaneous oxidation or, more familiarly, combustion. The same formula applies, so if you measure the difference between the rest mass of unburned material and the rest mass the burned object and gaseous byproducts, you’ll also get a tiny mass difference. Multiply it by  c2 and you’ll wind up with the energy set free during the chemical reaction.

We’ve all burned a match and there was no mushroom cloud, though. It can only follow that the square of the speed of light only partly explains the huge difference in energy released between nuclear and chemical reactions. Markus Pössel, the managing scientist of the Center for Astronomy Education and Outreach at the Max Planck Institute for Astronomy in Heidelberg, Germany, provides us with a great explanation for why nuclear reactions can be violent.

“To see where the difference lies, one must take a closer look. Atomic nuclei aren’t elementary and indivisible. They have component parts, namely protons and neutrons. In order to understand nuclear fission (or fusion), it is necessary to examine the bonds between these components. First of all, there are the nuclear forces binding protons and neutrons together. Then, there are further forces, for instance the electric force with which all the protons repel each other due to the fact they all carry the same electric charge. Associated with all of these forces are what is called binding energies – the energies you need to supply to pry apart an assemblage of protons and neutrons, or to overcome the electric repulsion between two protons.”

Nuclear binding energy curve. Credit: hyperphysics.phy-astr.gsu.edu

Nuclear binding energy curve. Credit: hyperphysics.phy-astr.gsu.edu

“The main contribution is due to binding energy being converted to other forms of energy – a consequence not of Einstein’s formula, but of the fact that nuclear forces are comparatively strong, and that certain lighter nuclei are much more strongly bound than certain more massive nuclei.”

Pössel goes on mentioning that the strength of the nuclear bond depends on the number of neutrons and protons involved in the reaction. What’s more, the binding energy is released both when splitting up a heavy nucleus into smaller parts (fission) and when merging lighter nuclei into heavier ones (fusion). This explains, along with chain reactions, why nuclear bombs can be so devastating.

How nuclear fission works

Nuclear fission is a process in nuclear physics in which the nucleus of an atom splits into two or more smaller nuclei as fission products, and usually some by-product particles.

Based on Albert Einstein’s eye-opening prediction that mass could be changed into energy and vice-versa, Enrico Fermi built the first nuclear fission reactor in 1940.

When a nucleus fissions either spontaneously (very rare) or following controlled neutron bombardment, it splits into several smaller fragments or fission products, which are about equal to half the original mass. In the process, two or three neutrons are also emitted. The resting mass difference, about 0.1 percent of the original mass, is converted into energy.

Nuclear fission of Uranium-235. Credit: Wikimedia Commons.

Nuclear fission of Uranium-235. Credit: Wikimedia Commons.

The energy released by a nuclear fission reaction can be tremendous. For instance, one kilogram of uranium can release as much energy as combusting 4 billion kilograms of coal.

To trigger nuclear fission, you have to fire a neutron at the heavy nucleus to make it unstable. Notice in the example above, fragmenting U-235, the most important fissile isotope of uranium, produces three neutrons.  These three neutrons, if they encounter other U-235 atoms, can and will initiate other fissions, producing even more neutrons. Like falling dominos, the neutrons unleash a continuing cascade of nuclear fissions called a chain reaction.

In order to trigger the chain reaction, it’s critical to release more neutrons than were used during the nuclear reaction. It follows that only isotopes that can release an excess of neutrons in their fission support a chain reaction. The isotope U-238, for instance, can’t sustain the reaction. Most nuclear power plants in operation today use uranium-235 and plutonium-239.

Another prerequisite for the fission chain reaction is a minimum amount of fissionable matter. If there is too little material, neutrons can shoot out of the sample before having the chance to interact with a U-235 isotope, causing the reaction to fizzle. This minimum amount of fissionable matter is referred to as critical mass by nuclear scientists. Anything below this minimum threshold is called subcritical mass. 

nuclear chain reaction

U-235 fission chain reaction. Credit: Wikimedia Commons.

How nuclear fusion works

Fusion occurs when two smaller atoms collide at very high energies to merge, creating a larger, heavier atom. This is the nuclear process that powers the sun’s core, which in turn drives life on Earth.

Like in the case of fission, there’s a mass defect — the fused mass will be less than the sum of the masses of the individual nuclei — which is the source of energy released by the reaction. That’s the secret of the fusion reaction. Fusion reactions have an energy density many times greater than nuclear fission and fusion reactions are themselves millions of times more energetic than chemical reactions.

Nuclear fusion is what powers the sun's core. Credit: NASA.

Nuclear fusion is what powers the sun’s core. Credit: NASA.

Nuclear fusion could one day provide humanity with inexhaustible amounts of energy. When that day may come is not clear at this point since progress is slow, but that’s understandable. Harnessing the same nuclear forces that drive the sun presents significant scientific and engineering challenges.

Normally, light atoms such as hydrogen or helium don’t fuse spontaneously because the charge of their nuclei causes them to repel each other. Inside hot stars such as the sun, however, extremely high temperature and pressure rip the atoms to their constituting protons, electrons, and neutrons.  Inside the core, the pressure is millions of times higher than the surface of the Earth, and the temperature reaches more than 15 million Kelvin. These conditions remain stable because the core witnesses a never-ending tug of war of expansion-contraction between the self-gravity of the sun and the thermal pressure generated by fusion in the core.

Due to quantum-tunneling effects, protons crash into one another at high energy to fuse into helium nuclei after a number of intermediate steps. Fusion inside the star, a process called the proton-proton chain, follows this sequence:

The proton-proton fusion process that is the source of energy from the Sun. Credit: Wikimedia Commons.

The proton-proton fusion process that is the source of energy from the Sun. Credit: Wikimedia Commons.

  1. Two pairs of protons fuse, forming two deuterons. Deuterium is a stable isotope of hydrogen, consisting of 1 proton, 1 neutron, and 1 electron.
  2. Each deuteron fuses with an additional proton to form helium-3;
  3. Two helium-3 nuclei fuse to create beryllium-6, but this is unstable and disintegrates into two protons and a helium-4;
  4. The reaction also releases two neutrinos, two positrons, and gamma rays.

Since the helium-4 atom has less energy or resting mass than the 4 protons which initially came together, energy is radiated outside the core and across the solar system.

To shine brightly, the sun gobbles about 600 million tons of hydrogen nuclei (protons) every second which it turns into helium releasing 384.6 trillion trillion Joules of energy per second. This is equivalent to the energy released in the explosion of 91.92 billion megatons of TNT per second. Of all of the mass that undergoes this fusion process, only about 0.7% of it is turned into energy, though.

Though scientists have been trying to harness fusion for decades, we’ve yet to fulfill the fusion dream that promises unlimited clean energy.

While it’s relatively easy to split an atom to produce energy, fusing hydrogen nuclei is a couple of orders of magnitude more challenging. To replicate the fusion process at the core of the sun, we have to reach a temperature of at least 100 million degrees Celsius. That’s a lot more than observed in nature — about six times hotter than the sun’s core — since we don’t have the intense pressure created by the gravity of the sun’s interior.

That’s not to say that we haven’t achieved fusion yet. It’s just that all experiments to date put more energy in enabling the required temperature and pressure to trigger significant fusion reactions than the energy generated by these reactions.

Promising new technologies like magnetic confinement and laser-based inertial confinement could one day surprise all of us with a breakthrough moment. One of the most important projects in the field is the  International Thermonuclear Experimental Reactor (ITER) joint fusion experiment in France which is still being built. Its doughnut-shaped fusion machine called tokamak is expected to start fusing atoms in 2025.

Elsewhere, in Germany, the Wendelstein 7-X reactor, which uses a complex design called a stellarator, was turned on for the first time late 2016. It worked as expected, though still inefficient like all other fusion reactors. The Wendelstein reactor, however, was built as a proof of concept for the stellarator design which adds several twists to the tokamak ring to increase stability. The UK and China have their own experimental fusion reactors as well. 

The United States, on the other hand, wants to significantly revamp the classical fusion reactor. Physicists at the Department of Energy’s Princeton Plasma Physics Laboratory (PPPL) are proposing a more efficient shape that employs spherical tokamaks, more akin to a cored apple.  The team writes that this spherical design halves the size of the hole in the doughnut, meaning we can use much lower energy magnetic fields to keep the plasma in place.

It seems like we’re still decades away from seeing an efficient fusion reactor. When we do get our own sun in a jar, though, be ready embrace the unexpected for nothing will be the same again.

Black Hole.

We’re made of stardust, but heavier elements are made of black-hole-and-neutron-star dust

Heavier chemical elements could be the love child of two very spectacular and exotic lovers — neutron stars and tiny black holes.

Black Hole.

“Papa?”
Image via Digitaltrends.

We are, as Carl Sagan once put it, “made of star stuff.” Considering that what we call a star is actually a ginormous reactor mashing hydrogen and helium atoms into more complex elements, such as carbon, oxygen, or iron, that’s pretty true. But we needn’t look very hard around us for elements that outshine our particularly starry heritage. R-process elements (which are much heavier than iron — such as gold or uranium) could be sired by nature’s two most extreme creations.

Stellar birth

So let’s take a step back and look at how elements form. The lightest, simplest atom, hydrogen, was created during of the Big Bang, with some helium and traces of lithium and beryllium peppered in. This mix started to clump together in areas of higher density (accrete), which eventually led to the formation of the first stars. Stars that formed more complex elements. But there is a caveat. A living star simply isn’t powerful enough to fuse stuff past iron. Even supermassive stars, the biggest out there, can’t do it.

Think of a star as an explosion so massive, its sheer weight and gravitational pull causes it to fall back on itself. So a star can only exist while there’s a balance between two forces — the energy of fusion reactions trying to blast it apart, and gravity straining to keep it together. This works quite well for our granddaddy’os up to the point where they build up a respectable silicon core.

Because, as aging stars everywhere find out, fusing silicon into iron doesn’t return on investment. Even in the ultra-hot, uber-dense conditions of a star’s core, making atoms merge takes a lot of energy — needed to overcome protons’ (positively charged particles) tendency to push other positively charged particles away. However, once you do make them merge, protons and neutrons get along just great thanks to the nuclear force, which makes them stick together.

The simpler the atom, the stronger this nuclear force. So when you go from hydrogen (1 proton) to helium (2 protons), and then on to lithium (3 protons) it gets progressively weaker — it has ‘less power’ so to speak. At the same time, all that leftover power needs to go somewhere and it does so by degrading into the heat and light of stars. But there is a turning point where you end up needing to pump more energy into the atom to make it fuse than you get from its final nuclear force.

The flip-side is that this turning point works both ways — that’s why fusion reactors work with hydrogen but fission reactors work with uranium. You can extract the extra energy by lowering the nuclear force of simple elements (hydrogen), or you can get it by splitting heavier atoms (uranium) and cashing back on the energy it took to fuse them together. But that’s a story for another time.

What matters right now is that this turning point is iron.

Ms and Mr Dense

Neutron star.

“Maman?!
Image credits Kevin Gill / Flickr.

Up to now, supernovas and binary star mergers were believed to be the only environments that could supply the conditions needed for higher fusion. But now, a team of three theoretical astrophysicists at UCLA — George Fuller, Alex Kusenko and Volodymyr Takhistov — offer another event that could produce these elements: the merger between a tiny black hole and a neutron star.

“A different kind of furnace was needed to forge gold, platinum, uranium and most other elements heavier than iron,” Fuller, a theoretical astrophysicist and professor of physics who directs UC San Diego’s Center for Astrophysics and Space Sciences and first author of the paper, explained in a statement.

“These elements most likely formed in an environment rich with neutrons.”

Neutron stars are immensely dense. They’re what’s left in the wake of stellar collapses and supernovae, a kernel of ultra-packed matter. A ‘normal’ atom has a nucleus, an electron shell, and a lot of empty space between the two. Neutron stars are like a huge atomic nucleus, made of back-to-back neutrons held together by gravity. To get an idea of what “immensely dense” means, it’s estimated that a spoonful of the stuff neutron stars’ surfaces are made of weighs about three billion tons.

The other half of this lovely couple is even denser — a tiny black hole, weighing between 10-14 and 10-8 solar masses. Unlike neutron stars, we’re not really sure that they really exist. But a lot of researchers (including Stephen Hawking) do believe they’re out there, a byproduct of the Big Bang, and could make up part of the dark matter — which has been proven to exist. If these micro black holes follow the distribution of dark matter in space, they’ll often co-exist with neutron stars. And this, the team argues, sets the stage for heavier elements to form.

Their calculations show that if a neutron star captures such a black hole and get devoured from the inside out by it, some of the dense neutron star matter can get thrown out into space by the ferocity of the event. Even a tiny bit of this matter is enough to seed the formation of a huge quantity of heavy elements, since it’s so dense.

“As the neutron stars are devoured,” Fuller explains, “they spin up and eject cold neutron matter, which decompresses, heats up and make these elements.”

“In the last milliseconds of the neutron star’s demise, the amount of ejected neutron-rich material is sufficient to explain the observed abundances of heavy elements.”

The team’s theory is especially intriguing since it also helps explain a few other unanswered questions about the universe. For example, it explains why there aren’t that many neutron stars in the galactic core, where there are a lot of black holes to hunt them down. Even more, the team says that the ejection of nuclear matter from tiny black holes chowing on neutron stars would explain three mysterious astronomical phenomena.

“They are a distinctive display of infrared light [‘kilonovas’], a radio emission that may explain the mysterious Fast Radio Bursts from unknown sources deep in the cosmos, and the positrons detected in the galactic center by X-ray observations,” Fuller concludes.

“Each of these represent long-standing mysteries. It is indeed surprising that the solutions of these seemingly unrelated phenomena may be connected with the violent end of neutron stars at the hands of tiny black holes.”

The paper “Primordial Black Holes and r-Process Nucleosynthesis” has been published in the preprint archive arXiv.

New measurement of a proton leaves us with more questions than answers

Six years ago, physicists announced the results of a new measurement of the proton — and the particle turned out to be too short. Since then, a lot of effort has been put into checking their results — and again, the latest measurements have revealed smaller than expected results. Physicists are now left scratching their collective heads trying to pin down the elusive measurements of this particle.

Image via Pixabay

Protons are positively charged particles that, together with neutrons, form the nuclei of atoms. They’re really, really tiny — for years, the proton’s radius was set at about 0.877 femtometers. One femtometer being equal to 10−15 meters, slightly over a quadrillionth of a meter in diameter. This number, however, was changed in 2010, when Randolf Pohl from the Max Planck Institute of Quantum Optics in Germany used a novel measuring technique and got a better measurement for a proton’s size.

His team started from a simple hydrogen atom — which has one proton and one electron — and substituted its electron for a heavier particle called a muon. They then fired a laser at the altered atom, measuring the resulting change in its energy levels to calculate the size of the nucleus — which in the case of hydrogen is a single proton. They reported that their measurement of the particle came out 4% smaller than what other methods showed.

Measurements performed in 2013 confirmed the findings, setting the world of particle physics ablaze trying to find the answer to the “proton radius puzzle.”

Pohl also applied this technique to deuterium, a hydrogen isotope with one proton and one neutron — also known as a deutron in this case — in the nucleus. Accurately calculating the size of the deutron took plenty of time. Today, the team published the long-awaited result and, you’ll never guess it, it came up short again, this time by 0.8%.

Evangeline J. Downie at the George Washington University in Washington DC says that these numbers show the proton radius puzzle is here to stay.

“It tells us that there’s still a puzzle,” says Downie. “It’s still very open, and the only thing that’s going to allow us to solve it is new data.”

Several other similar experiments, both at Pohl’s and other labs around the world, are already underway. One such experiment will re-use the muon technique to measure the nucleus size of heavier atoms, such as helium.

Pohl believes the issue may not be with the proton itself, but rather with an incorrect measurement of the Rydberg constant which describes the wavelengths of light emitted by an excited atom. This constant’s value has been established very precisely in other experiments however, so something has to have gone really wrong for it to be inaccurate.

One other explanation proposes new particles that cause unexpected interactions between the proton and the muon, without changing its relationship with the electron. That could mean that the key to the puzzle lies beyond the standard model of particle physics.

“If at some point in the future, somebody will discover something beyond the standard model, it would be like this,” says Pohl.

How Albert Einstein broke the Periodic Table

In a study published in the January 19, 2016 issue of the Journal of the American Chemical Society (JACS), scientists at Tsinghua University in China confirmed that something very unusual is happening inside extremely heavy atoms, causing them to deviate from their expect chemical behavior predicted by their place on the Periodic Table of Elements. Due to the velocity of electrons in these heavy elements getting so close to the speed of light, the effects of special relativity begin to kick-in, altering the chemical features observed.

The study shows that the behavior of the element Seaborgium (Sg) does not follow the same pattern as the other members of its group, which also contain Chromium (Cr), Molybdenum (Mo), and Tungsten (W). Where these other group members can form diatomic molecules such as Cr2, Mo2, or W2, using 6 chemical bonds, diatomic Sg2 forms using only 4 chemical bonds, going unexpectedly from a bond order of 6 to a bond order of only 4. This is not predicted by the periodic nature of the table, which itself arises from quantum mechanical considerations of electrons in energy shells around the nucleus. So what’s happening here? How does relativity throw off the periodic pattern seen in our beloved table of elements?

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 to the elements as they went from light weight 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. See figure 1.

 

Mendeleev's 1871 version of the periodic table. Blank spaced were provided where predicted new elements would be found.

Figure 1.   Mendeleev’s 1871 version of the periodic table. Blank spaced were provided where predicted new elements would be found.

 

Once quantum theory was developed in the early 20th century, the explanation for the periodic behavior of the table became apparent. The electrons in the atom are arranged in orbital shells around the nucleus. There are several different orbital types, again based on predictions from quantum mechanics, and each type of orbital can hold only a specified number of electrons before the next orbital has to be used. As you go from top to bottom in the Periodic Table, you use orbitals of progressively higher energy levels. Periodic behavior arrises because, although the energy levels keep getting higher, the number of electrons in each orbital type are the same for each group, going from top to bottom. See figure 2.

 

Figure 2. Group 1 as an example of a group in the Periodic Table. As the group goes from top to bottom the energy levels get higher and the elements get heavier.

Figure 2.   Group 1 as an example of a group in the Periodic Table. As the group goes from top to bottom the energy levels get higher and the elements get heavier.

 

The other great area of physics developed in the early 20th century was relativity, which didn’t seem to have much importance on the scale of the very small. Albert Einstein published his ground breaking paper on Special Relativity (SR) in 1905, which described the effects on an object moving close to the speed of light. In 1915 he developed the General Theory of Relativity (GTR), describing the effects due to a massive gravitational field. It is SR that becomes an important consideration in the very heavy elements due their electrons reaching velocities at a significant percentage of the speed of light.

Einstein showed that as the velocity of an object approaches the speed of light its mass increases. This effect is too small to be noticeable at everyday speeds, but becomes pronounced near light speed. It can also be shown that the velocity of an electron in orbit around an atom, is directly proportional to the atomic number of the atom. In other words, the heavier the atom, the faster its outer electrons are moving. For the element hydrogen, with atomic number 1, the electron is calculated to be moving at 1/137 the speed of light, or 0.73% of light speed. For the element gold (Au) with atomic number 79, the electrons are moving at 79/137 the speed of light, or 58% of light speed, and for Seaborgium (Sg) with atomic number 106, the electron is going at an impressive 77% of light speed. At these speeds the crazy effects of special relativity kick-in making the electron mass significantly heavier than it is at rest. For gold this makes the electron 1.22 times more massive than at rest, and for Seaborgium the electron’s mass comes out to be 1.57 times the electron rest mass. This, in turn, has an effect on the radius of the electron’s orbit, squeezing it down closer to the nucleus.

Some relativistic effects have already been known for certain heavy elements. The color of gold, for instance, arises due to the effects of relativity acting on it’s outer electrons, altering the energy spacing between two of it’s orbitals where visible light is being absorbed, and giving gold it’s characteristic color. If not for these relativistic effects, gold would be predicted to appear whitish.

For the elements in Group 6 of the Periodic Table (Cr, Mo, and W) (see Figure 3.) that were studied in the JACS article, they each have five d-orbitals and one s-orbital capable of forming bonds with another atom. Sg breaks the periodic pattern because it’s highest energy s-orbital is so stabilized by the effects of it’s relativistically moving electron, it doesn’t contribute to bonding. Due to the intricacies inherent in molecular orbital theory, this drops the number of bonding orbitals from 6 in Cr, Mo, and W, to only 4 in Sg (even though Sg is a group 6 member). It also means that the bond between Sg and Sg in the Sg2 molecule is 0.3 angstroms longer than expected, even though the Sg radius is only 0.06 angstroms bigger than W. If relativity didn’t have an effect, then the Sg2 molecule would be joined together by 6 orbital bonds, like any respectable Group 6 element should be! The same effect was also found in the Group 7 elements, with Hassium (Hs) showing the drop in bond order due to relativistic effects, just as Sg.

 

Figure 3. A modern version of the Periodic Table of Elements. Notice the Group 6 elements Cr, Mo, W, and Sg.

Figure 3.   A modern version of the Periodic Table of Elements. Notice the Group 6 elements Cr, Mo, W, and Sg.

 

The periodic table of elements is an impressive scientific achievement, who’s periodicity reveals an underlying order in nature. While this periodicity works remarkably well, the few exceptions to the rule also uncover important principles at work. Einstein’s theory of relativity breaks the periodic table in some interesting and unexpected ways. It’s the very heavy elements on the chart that don’t show good “table” manners, thanks to Einstein.

 

Journal Reference and other reading:
1. Relativistic Effects Break Periodicity in Group 6 Diatomic Molecules Yi-Lei Wang, Han-Shi Hu*, Wan-Lu Li, Fan Wei, and Jun Li*
Department of Chemistry & Key Laboratory of Organic Optoelectronics and Molecular Engineering of Ministry of Education, Tsinghua University, Beijing 100084, China  J. Am. Chem. Soc., 2016, 138 (4), pp 1126–1129 DOI: 10.1021/jacs.5b11793 Publication Date (Web): January 19, 2016

2. Relativistic effects in structural chemistry Pekka Pyykko Chem. Rev., 1988, 88 (3), pp 563–594 DOI: 10.1021/cr00085a006 Publication Date: May 1988

3. Why is mercury liquid? Or, why do relativistic effects not get into chemistry textbooks? Lars J. Norrby J. Chem. Educ., 1991, 68 (2), p 110
DOI: 10.1021/ed068p110 Publication Date: February 1991

An atomically assembled array of 96 iron atoms containing one byte of magnetic information in antiferromagnetic states. (c) IBM Research-Almaden

IBM develops smallest storage device: 12 atoms for a single bit!

Each little green bump is an atom of ferromagnetic material. All these 12 atoms captioned above form an array capable of storing on bit of information. (c) IBM

Each little green bump is an atom of ferromagnetic material. All these 12 atoms captioned above form an array capable of storing on bit of information. (c) IBM

Moore’s law states that the level of technology and computing power should double every two years, and so far the postulate hasn’t been wrong in more than 50 years. A group of IBM scientists have now managed to develop a data storage technique which allows for information to be stored with as little as 12 atoms, thousands of times less atoms than it is currently required for a single bite. Gordon Moore, the Intel co-founder, would have been proud.

Storing a single bit of data on a disk drive requires one million atoms of magnetized storage medium, and this is valid only for the most advanced storage devices currently available today. The new research from IBM suggests that, eventually, in the not so distant future storage devices could be developed at 1/83,000th the scale of today’s disk drives.

“Magnetic materials are extremely useful and strategically important to many major economies, but there aren’t that many of them,” said Shan X. Wang, director of the Center for Magnetic Nanotechnology at Stanford University. “To make a brand new material is very intriguing and scientifically very important.”

The current magnetic storage devices, like the hard-drive currently in use by your computer which basically allows for information like the one on this website to be read and stored, are made out of ferromagnetic materials like iron or nickel. When these materials are exposed to a magnetic field, their magnetic poles line up in the same direction. These materials have worked very well until now, as far as conventional hard drives or micro chips are concerned, however when miniaturization is concerned, at a certain scale bits start to interfe with each other. Antiferromagnetism works in the opposite direction, with a highly important distinction – the orbits of unpaired electrons don’t align to the same direction. Thus atoms in manganese oxide, a material that works well for this, atoms align head to foot such that the North magnetic pole of each atom seeks the South magnetic pole of the other.

Using antiferrogmanetism, the team of researchers from IBM’s Almaden Research Center, led by Andreas Heinrich, managed to create a swathe of material with a much denser magnetic pallet than conventional ferromagnetic devices.  The researchers used a scanning tunneling microscope, a device the size of a washing machine, not only to pin point at an atomic scale, but also accurately position individual atoms together, and engineer 12 antiferromagnetically coupled atoms. This is the the smallest number of atoms with which one can create a magnetic bit in which it is possible to store information.

Heading towards a golden computing age

An atomically assembled array of 96 iron atoms containing one byte of magnetic information in antiferromagnetic states. (c) IBM Research-Almaden

An atomically assembled array of 96 iron atoms containing one byte of magnetic information in antiferromagnetic states. (c) IBM Research-Almaden

To demonstrate the antiferrogmantic storage effect, the IBM researchers created a computer byte, the equivalent of one character, out of an individually placed array of 96 atoms.   They then used the array to encode the I.B.M. motto “Think” by repeatedly programming the memory block to store representations of its five letters.  Also, as if the sheer scale of this technology wasn’t amazing enough, the IBM researchers observed that, albeit in very small numbers the atoms display some quantum mechanical characteristics – simultaneously existing in both “spin” states, in effect 1 and 0 at the same time. This could have remarkable implications for quantum computing development.

This technology might take many years for regular consumers to experience

Now, although this latest gem from IBM will allow for storage devices to be built at a fraction of the current size and power consumption, don’t expect it to become commercially available to the general public for a pretty long while. The researchers were capable of holding on to a data bit for several hours at a temperature close to absolute zero, along with other conditions remarkably difficult to reach. Also, manufacturing-wise it will take some time probably before an automatic method of arranging, placing and manipulating individual atoms in the proper array.

“It took a room full of equipment worth about 1 million dollars and a whole lot of sweat,” to get the 96-atom configuration to work, Heinrich said. “The atoms are in a very regular pattern because we put them there. “Nobody knows how to make that cost effective in manufacturing…that’s the core issue of nanotechnology.

via NYT

CERN is back in business with the first collisions

lhc

The researchers and engineers operating the Large Hadron Collider have smashed together for the first time protons, in what is considered a huge step forward by pretty much everybody working at the huge physics experiment.

The particles were accelerated on Monday, through the LHC’s 27 km and then ‘drove’ into each other, in an attempt to recreate the conditions that took place a few moments after the Big Bang. This attempt is crucial for our understanding of physics, and here’s why.

Researchers are trying to find signs of what has been called the Higgs boson. This subatomic particle lies at the foundation of our understanding of particle physics, but despite the fact that it’s so important, we have yet to actually discover it. It’s expected that the LHC will provide the sought after particle and confirm our current theories. However, if not, we may be forced to rethink pretty much all of our particle physics.

The people operating this amazing particle accelerator seem quite ecstatic, as you can see below.

cern

“It’s a great achievement to have come this far in so short a time,” said Cern’s director-general Rolf Heuer. But we need to keep a sense of perspective – there’s still much to do before we can start the LHC physics programme.”

Fabiola Gianotti, spokesperson for the Atlas scientific team, commented: “This is great news, the start of a fantastic era of physics and hopefully discoveries after 20 years’ work by the international community.”

We’ll keep you posted with what’s going on at the LHC, and we’re pretty psyched to see how things are going. There’s definitely more to come.

First Universal Two-Qubit quantum processor created

qbitPhysicists from NIST (National Institute of Standards and Technology) have demonstrated what they claim to be the first universal programmable quantum information processor that will be able to run any program allowed by quantum mechanics (the set of principles that describe the atomic and subatomic matter). They managed to accomplish this using two quantum bits (qubits) of information.

This processor could prove to be a major breakthrough for a future quantum computer, that could very well be the ‘evolutionary leap’ in the computers’ life thus resulting the possible solve of problems that are untouchable today. The discovery was presented in the latest edition of Nature Physics and this marks the first time anybody has moved beyond asking a single task from a quantum computer.

“This is the first time anyone has demonstrated a programmable quantum processor for more than one qubit,” says NIST postdoctoral researcher David Hanneke, first author of the paper. “It’s a step toward the big goal of doing calculations with lots and lots of qubits. The idea is you’d have lots of these processors, and you’d link them together.”

The processor basically stores binary information in just two beryllium ions held in an electromagnetic ‘trap’, and then handled with ultraviolet lasers. With these in hand, the NIST team managed to perform 160 different processing routines using just the two qubits. Although practically there is an infinite number of programs you can perform with the two qubits, the 160 are pretty much totally relevant, and they prove that the processor is “universal”, Hanneke says.

Of course there will be many more qubits and logic operations to solve bigger problems, but when you come to think about it, all this was done with just two atoms, basically; and the operations they performed were no easy task. Each program consisted of 31 logic operations, 15 of which were varied during programming.

Meet the world’s most powerful X-Ray laser

homerThe first experiments with this laser (Linac Coherent Light Source) have been given the green light at the Department of Energy’s SLAC National Accelerator Laboratory. The illuminating of objects and processing speed will take place at an unprecedented scale, promising groundbreaking research in physics, chemistry, biology and numerous other fields.

“No one has ever had access to this kind of light before,” said LCLS Director Jo Stöhr. “The realization of the LCLS isn’t only a huge achievement for SLAC, but an achievement for the global science community. It will allow us to study the atomic world in ways never before possible.”

Early experiments are already showing some promise, providing insight on fundaments of atoms and molecules, underlying their properties. The short term goal is to create stop action frames for molecules in motion. By putting together many of these images to create a film, scientists will create for the first time a film with actual molecules in motion, being able to see chemical molecules bond and break, as well as actually see how atoms interact at a quantum level.

“It’s hard to overstate how successful these first experiments have been,” said AMO Instrument Scientist John Bozek. “We look forward to even better things to come.”

Meet the magnetic superatoms

dadaVirginia Commonwealth University managed to discover what they have called a ‘magnetic superatom‘, a stable cluster of atoms that can ‘impersonate’ various elements from the periodic table, that could be put to use in numerous fields, especially for biomedical purposes and to create molecular devices for the next generation of computer memory.A team from the

This cluster consists of one atom of vanadium and eight cesium. Together, they act like a tiny magnet that mimics a single manganese atom in magnetic strength but allows electrons with certain spin orientations to flow through the surrounding shell atoms.

The team was led by Shiv N. Khanna, Ph.D., professor in the VCU Department of Physics, together with VCU postdoctoral associates J. Ulises Reveles, A.C. Reber, and graduate student P. Clayborne, and collaborators at the Naval Research Laboratory in D.C., and the Harish-Chandra Research Institute in Allahabad, India; they teamed up together to go against what can only be called a titanic quest, namely examining the magnetic and electronic properties of the clusters.

They found out that the eight cesium atoms provide extra stability due to a filled electronic state. Also, when one atom combines with others, it tends to lose or gain valence until it reaches stable configuration. As Khanna points out:

“An important objective of the discovery was to find what combination of atoms will lead to a species that is stable as we put multiple units together. The combination of magnetic and conducting attributes was also desirable. Cesium is a good conductor of electricity and hence the superatom combines the benefit of magnetic character along with ease of conduction through its outer skin,” Khanna said. A combination such as the one we have created here can lead to significant developments in the area of “molecular electronics,” a field where researchers study electric currents through small molecules. These molecular devices are expected to help make non-volatile data storage, denser integrated devices, higher data processing and other benefits,” he said.