Seeing A Single Atom With The Naked Eye?

This is not a critique of the winning photo. Rather, it is an example of a "click bait", where the news report tries to entice you to read it because the title is so astounding. I guess it worked on me.

This news report, purportedly from Popular Mechanics, is highlighting a winning science/engineering photo of a single strontium atom being held in an ion trap. But what it says is a bit misleading:

Now, we have a photograph that shows a single atom floating in an electric field, and it's large enough to see without any kind of microscope.

This is wrong. It is not "large enough" to be seen.

They corrected this somehow later in the article, but it still does not dispel the error that this has nothing to do with size, and it requires a bit of elementary knowledge of atomic energy level to realize that the earlier description is a mistake.

The strontium atom in the photo is hit by a high-powered laser, which causes the electrons orbiting the strontium atom to become more energized. Occasionally, these energized electrons will give off light. With enough energized electrons giving off enough light, it's possible for an ordinary camera to image the atom.

In other words, the strontium atom was excited and this then causes it to emit light. This process is no different than the light that you see from neon signs or your fluorescent light bulb that has mercury vapor. The unique part about this setup is that you are seeing light from a single atom, whereas in your neon signs, you are seeing the light from many, many atoms. But the process is identical! Yet, we don't go ga-ga and proclaim that we can see an atom with our naked eye.

Just be clear, you are not seeing the atom in the normal sense. You are seeing the light from an atomic transition of this strontium atom. The fact that this is made by a captured single atom is remarkable. The fact that we can detect light from this atom with our "naked eye" does not mean that we are "seeing" the atom in the normal sense that most people understand it.

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Light From A Single Strontium Atom

The image of light from a single strontium atom in an atom trap has won the Engineering and Physical Sciences Research Council photography competition.

You can see a more detailed photo of it on Science Alert.

Unfortunately, there is a bit of misconception going on here. You are not actually seeing the single strontium atom, because it highly depends on what you mean by "seeing". The laser excites the single strontium atom, and then the strontium atom relaxes and releases energy in the form of light. This is the light that you are seeing, and it is probably a result of one or more atomic transition in the atom, but certainly not all of it.

So you're seeing light due to the atomic transition of the atom. You are not actually seeing the atom itself, as proclaimed by some website. This is the nasty obstacle that the general public has to wade through when reading something like this. We need to make it very clear when we report this to the media on what it really is in no uncertain terms, because they WILL try to sensationalize it as much as they can.

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Hot Atoms Interferometer

This work will not catch media attention because it isn't "sexy", but damn, it is astonishing nevertheless.

Quantum behavior are clearly seen at the macroscopic level because of the problem in maintaining coherence over a substantial length and time scales. One of the ways one can extend such scales is by cooling things down to extremely low temperatures so that decoherence due to thermal scattering is minimized.

So it is with great interest that I read this new paper on atoms interferometer that has been accomplished with "warm" atomic vapor[1]! You also have access to the actual paper from that link.

While the sensitivity of this technique is significantly and unsurprisingly low when compared to cold atoms, it has 2 major advantages:

However, sensitivity is not the only parameter of relevance for applications, and the new scheme offers two important advantages over cold schemes. The first is that it can acquire data at a rate of 10 kHz, in contrast to the typical 1-Hz rate of cold-atom LPAIs. The second advantage is the broader range of accelerations that can be measured with the same setup. This vapor-cell sensor remains operational over an acceleration range of 88g, several times larger than the typical range of cold LPAIs.

The large bandwidth and dynamic range of the instrument built by Biedermann and co-workers may enable applications like inertial navigation in highly vibrating environments, such as spacecraft or airplanes. What’s more, the new scheme, like all LPAIs, has an important advantage over devices like laser or electromechanical gyroscopes: it delivers acceleration measurements that are absolute, without requiring a reference signal. This opens new possibilities for drift-free inertial navigation devices that work even when signals provided by global satellite positioning systems are not available, such as in underwater navigation.

And again, let me highlight the direct and clear application of something that started out as simply appearing to be a purely academic and knowledge-driven curiosity. This really is an application of the principle of superposition in quantum mechanics, i.e. the Schrodinger Cat.

This is an amazing experimental accomplishment.

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[1] G. W. Biedermann et al., Phys. Rev. Lett. 118, 163601 (2017).

Newton Lecture 2014

The 2014 Newton Lecture given by Deborah Jin, who to me, already deserves a Nobel Prize in physics.



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Don't Miss Looking At The Trees Due To The Forest

This is a report on a proposal to enable us to view a "movie" of a Rydberg atom:

In addition to having a large electron cloud, an unusual feature of a Rydberg atom is that its highly excited electron can exist as a coherent superposition of several different atomic orbitals. These orbitals interfere with each other, which means that the electron cloud changes shape with time. These fluctuations are much slower than the movement of electrons nearer the atomic nucleus, which is why Kirrander and Suominen argue that the fluctuations could be tracked by firing intense and coherent pulses of X-rays at the atoms.

Such pulses can be produced at accelerator-based free-electron lasers such as the Linac Coherent Light Source (LCLS) at the SLAC National Accelerator Laboratory in California or the X-ray Free Electron Laser (XFEL), which is set to come online at DESY in Hamburg, Germany in 2016. Kirrander and Suominen have also calculated that the motion of the corresponding "electron hole" in the atom – the superposition of inner orbitals that the electron has left behind – can be visualized as well. As the inner electrons are involved in chemical reactions, the new technique could therefore be a powerful tool for chemists.

When I said not to miss looking at the trees, most people reading the article will be enamored by the proposal that we can actually view such a thing in real time, that we can see the evolution of such an atom, and the potential that we can view the dynamics of a lot more system having such short time-scale. These are the "forest".

The trees here, which *I* am more interested in, and what most people will have missed, is the advancement made in accelerator physics that allows the ability to make such a measurement. The instrument being used is within the realm of accelerator physics, and specifically, the study of beam physics and engineering. This field of physics is often the unsung hero that enables the advancement in many other fields of physics. Think of what the LHC and the Tevatron could do without advanced knowledge of accelerator physics.

And this brings us to a very important point here. Many areas of science can only advance in knowledge when they have the ability to perform the experiments that they want. Inevitably, this means that that they have the equipment and tools to be able to do these experiments. This ranges from high-spatial-resolution instrument to high-temporal resolution detectors. In other words, they depend on others to provide them with the instruments to advance their knowledge.

It also means that if you kill research in these grass-roots areas, you are killing more than just one area. When a lion killed the nursing mother of deer, for example, that lion took not one, but two lives with that kill. When funding for many of these areas of physics is severely reduced, the chain reaction and impact can trickle very quickly down stream. It affects the advancements in many other fields that would have gotten the benefit from it. Think of how many different usage of facilities such as a synchrotron light source or a free-electron laser.

So when you read an article such as this, don't miss paying attention to the fact that these proposed abilities to do such-and-such are benefiting from the advancement and investment in another field that you might have not realized. The interconnectedness of science is never more apparent than in an example such as this.

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First Direct Measurement of Van der Waals Force

In an amazing feat of experimental ingenuity, the first direct measurement of Van der Waals force between two atoms has been accomplished.

This latest research was done by researchers at the Laboratoire Charles Fabry (LCF) in Palaiseau and the University of Lille. "What we have done here, for the first time to our knowledge, is to measure directly the Van der Waals interaction between two single atoms that are located at a controlled distance, chosen by the experimenter," says Thierry Lahaye, who is part of the LCF team.

Controlling the distance between normal atoms – while measuring the force between them – is extremely difficult because the relevant distances are tiny. To get round this problem the team used Rydberg atoms, which are much larger than normal atoms. Such atoms have one electron in a highly excited state. This means that they have a very large instantaneous dipole moment – and therefore should have very strong Van der Waals interactions over relatively long distances. They also have unique properties that allow them to be controlled with great precision in the lab.

You can also read more review of this work at APS Physics, and, get a free copy of the paper.

Nice piece of work.

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Neils Bohr Between Physics And Chemistry

If you had missed this free article from month's issue of Physics Today, well then, don't miss it. It deals with Neils Bohr model of the atom, and how that contributes to chemistry and physics.

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Catch And Release Of Photons

I'm always amazed by the nature of these experiments, and continue to be awed by what have been accomplished.

Two different groups published two different papers in this week's PRL, all reporting on the ability to store photons and then releasing them. What is even fascinating is that each group used different schemes to accomplish the same thing. I already reported on one of these results earlier. So check out the first link for a review of these two experiments, and you also get a link to free access to both papers.

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Store Photons. Then Make Them Intract With Each Other

It's amazing to see the development in this area. Just a few years ago, we were amazed at the accomplishments coming out of Lene Hau's lab in being able to not only store photons, but also to "replay" them back. Now comes this, which is another step in refining and improving the capability of storing photons.

What Charles Adams and colleagues at Durham University have now done is come up with a way of storing individual optical photons in highly excited states of an atomic gas. Once stored, the photons can be made to interact strongly, before being released again. An important feature of the technique is that it uses microwaves, which are also used to control some types of stationary qubit. 

 http://arxiv.org/pdf/1207.6007v3.pdf

Apparently, this is to be published in PRL.

Definitely a commendable accomplishment here in the evolution of our capability of using photons for quantum communications.

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The Origins of the Elements

If you have an hour to spare, here's something you might either want to watch, or just listen in the background.



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Why Is Li Atom Ground State In a 1s2 2s Configuration?

You would think that something that is well-established in both physics and chemistry textbooks would not reveal any more surprises, but you (and we) are wrong.

This is an interesting preprint, and it got me captivated for several minutes. First of all, let's set the scenario.

In the periodic table, as one go from H to higher numbered atoms, one start filling up various atomic orbitals. So you have H having 1s^1, He with 1s^2, Li with 1s^2 2s^1, etc.. etc. The interesting thing here is that with just the electron-ion interaction being accounted for, the 2s and 2p states in Li are degenerate, meaning they both have the same energy. So why would the 2s state gets filled first ahead of the 2p?

The standard textbook explanation here is that the 2p states, due to the geometry of the orbitals, tend to get shielded more by the 1s electrons than the 2s states. Thus, the 2p states have a higher energy than the 2s states.

This preprint claim that that explanation is flawed. They showed that what is really at play here is the electron-electron interaction, which is often neglected in many of these multi-electron systems with low atomic number. In their calculation, the interaction between 1s - 2s electrons produced a lower energy state than the interaction between 1s - 2p electrons. This is the main reason for Li ground state to be what it is, and not due to "shielding".

I'm sure this is being submitted for publication somewhere. The paper is not that difficult to follow for advanced undergraduate physics students.

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Optical Atomic Clock Outperforms Cesium Clock

Our expertise in Metrology seems to be improving quite dramatically nowadays. This is one such example.

Now, in Physical Review Letters, Alan Madej and colleagues at the National Research Council in Canada report they have greatly increased the accuracy with which another atomic frequency standard, the optical transition in an isolated strontium ion, can be measured. Furthermore, the precision of their frequency measurement now supersedes that of the existing cesium standard, which could lead to the adoption of a new frequency standard for defining the second as the basic unit of time.

You can get a free copy of this paper at the link provided above.

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X-Ray Laser From Atoms

Another stunning accomplishment. We now have a first documented evidence of the generation of x-rays from atoms, with the help of x-rays generated from an accelerator.

The new atomic x-ray laser won't replace the LCLS and other accelerator-based systems. In fact, to make the atomic laser work, researchers blasted neon atoms with x-rays from the LCLS itself. Still, the results mark a conceptual triumph, fulfilling a 45-year-old prediction that such an atomic x-ray laser is possible. "Nobody had done this before, and everybody knew that somebody had to go out and do this," says Philip Bucksbaum, director of SLAC's PULSE Institute for Ultrafast Energy Science in Menlo Park, California, who was not involved in the work. "So this is great."

It'll be interesting to see if they can turn this into a useful device, at least before an x-ray FEL catches up on producing similar quality x-ray beams.

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The Road To Discovery Of Atom's Nucleus

This is an interesting and brief historical account Ernest Rutherford's discovery of the nucleus.

The one interesting part that I read is how shrewd he was.

With blossoming international scientific fame, Rutherford was regularly offered posts in America and elsewhere. He accepted none because McGill had superb laboratories and support for research, but he was wise enough to let the McGill authorities know of each approach; they increased his salary each time. However, Rutherford also wished to be nearer the centre of science, which was England, where he would have access to excellent research students and closer contact with notable scientists. His desire was noted. Arthur Schuster, being from a wealthy family, said he would step down from his chair at Manchester University provided that it was offered to Rutherford, and in 1907 Rutherford moved to Manchester.

As always, in reading historical account such as this, it continues to amaze me how many "household names" are involved, either directly or indirectly. We see the involvement of Geiger, Marsden, Bohr, etc...

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309 Antihydrogen Trapped for 1000 Seconds

This made the news at least a week ago, but only now has the story appeared on PhysicsWorld, so here it is.

The ALPHA team produced the antihydrogen by merging two clouds of cold plasmas: one containing positrons and the other antiprotons. By improving their trapping techniques, the researchers managed to hold the antihydrogen for more than 1000 s. These advances also meant that five times as many atoms were trapped per attempt. Calculations based on data from the experiment suggest that after about 0.5 s, most of the trapped antihydrogen atoms reach their lowest energy or ground state. As a result, the team says that its trapped sample is the first antihydrogen obtained in the ground state.

As in this group's earlier attempt, this is such an amazing accomplishment. The fact that they can hold these that long opens up a whole slew of tests that one can conducts on very fundamental aspects of physics. So this isn't just an astounding accomplishment, but also a tool to investigate other things. That is why this is so important.

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A Brief Review of Atoms .... After A Flirt At A Supermarket

I initially didn't know what to make of this. It started out with a story of an 8-year old calling the woman behind him "old". I think most men would get a slap on the face for doing that. Still, it turned into a rather humorous flirting.

And if you can get past that, there's a rather concise description of atoms, especially the role of neutrons in atoms! I suppose the "connection" here is that both the boy and neutrons are "social butterfly".

Er..... oookaayyy.....

I'm guessing that this is part of a series, and this is one of the middle article.

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Storing Light For 1.5 Seconds

Lene Hau and her group at Harvard has done it again! After demonstrating the ability to "stop light" several years ago, they now have shown that they can store that light for longer than milliseconds - this time, up to 1.5 seconds, which is LONG at the time scale that we are typically used to when dealing with light. You can also read more about this work here.

Now, one has to realize that we can "stop light" very trivially. Shine your flashlight onto a black surface, and voila! You've stopped light. However, what is done here isn't that. Stopping light, in this case, means that the light's energy AND PHASE, are somehow captured temporarily, and then it is then retransmitted later on. This can't be done when you stop light with a piece of paper, let's say, because you can't 'replay' what you had captured - most of the energy is lost in the vibrational energy of the stopping material. So that's why this "stopping light" experiment is different and not easy, and such a big deal. The ability to store and then replay exactly what came in is what makes it such an amazing feat.

Edit: This paper is available, "free-to-read" at the PRL website.

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First Detailed Photos of Atoms

You'd be amazed that, to this day, there are "people" (I put that word in quotes because I often wonder if crackpots are really people) who still dispute the QM description of the atom. It's the same disease as those people who still think we didn't land on the moon or that the earth is flat, I suppose.

Well, chalk this up to another one of those "the more they test it, the more convincing it becomes". Using field-emission electron microscope, we can now really map the electronic orbitals. And SURPRISE! It clearly matches QM's description!

Quantum mechanics states that an electron doesn't exist as a single point, but spreads around the nucleus in a cloud known as an orbital. The soft blue spheres and split clouds seen in the images show two arrangements of the electrons in their orbitals in a carbon atom. The structures verify illustrations seen in thousands of chemistry books because they match established quantum mechanical predictions.

I'll edit this and put in the exact reference when the paper is out.

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An Astronomical Solution to an Old Quantum Problem

This is a fascinating review of a very interesting paper. It is using an established concept that is "common" in astronomy, i.e. a satellite orbit around the earth-sun system exhibiting Lagrange points, and applying it to the electron orbits around the nucleus.

Now, in results reported in Physical Review Letters, H. Maeda (Japan Science and Technology Agency, Tokyo), J. H. Gurian, and T. F. Gallagher (University of Virginia) have beautifully demonstrated in the laboratory a solution to this problem of the spreading atomic electron wave packet using a trick that was discovered in astronomy long before the problem arose in quantum theory [3]. When a small satellite moves in a sun-earth system there are five stable points at which the satellite remains fixed with respect to the rotating sun-earth system (Fig. 1). These are the famous Lagrange L points. In 1994 Bialynicki-Birula et al. showed that stable Lagrange points could be produced in the atomic electron problem by applying a circularly polarized microwave field rotating in synchrony with an electron wave packet in a highly excited state (a so-called Rydberg atom) [4]. The electron wave packet then remains localized near the Lagrange point while circling the nucleus indefinitely. Effectively the atom is made to behave quite classically.

Don't forget that you can get a free copy of the original paper from that link.

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Steven Chu Is Still Not Too Busy To Do Science

I certainly missed this one, which is understandable because it was uploaded in a section of ArXiv that I don't normally read.

On the day that Steven Chu was undergoing his confirmation hearing for the Secretary of the Dept. of Energy position, his research paper was posted on ArXiv by one of his co-author. Not that this is a surprise considering everything we know about him already. Besides, this was done when he is the Director of Lawrence Berkeley Lab, and it is not unusual for a Nat'l Lab director to still continue doing physics research work.

Still, I wonder how much of this can he still do after he becomes the head of DOE. Will he have time to continue doing or be involved in research work, even on the peripheral? Can it also be a conflict of interest? Or maybe he'll work alone and produce papers more on ABOUT physics, rather than physics itself, such as the one done by the out-going Presidential Science Advisor John Marburger.

In any case, he will have his hands full, that's for sure.

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