When non-scientist friends and family ask me the dreaded question "What's the aim of your work?", I'm never quite sure how to frame my answer. This is particularly true when I'm asked "Aren't scientists looking for the ultimate truth?" (no, we're looking for grant money and pizza). Lately, I've come up with a reply that I think helps me explain my aims while remaining relatively agnostic about the realist vs. instrumentalist debate:
I tell them I'm a cartographer.
As to one of those obligations, I will be presenting a poster at the upcoming Midwest Theoretical Chemistry Conference (MTCC) at Northwestern University on Sunday, June 15th. I will be presenting poster number 14 in session B from 4:30 to 6:00 PM in Silverman Hall . The title of my poster is Interplay of Coupling Strength and Dephasing Noise in Excitonic Transfer in One- and Two-Dimensional Homogeneous Systems. The research is still very much ongoing, but when's the last time you heard of a complete and finished scientific work?
If you're attending the MTCC please do drop by. Since I'd imagine only a handful of readers will be attending, I will try to publish the content of my poster on the blog at some point, although unfortunately that may not be for a while.
In the paper, the evidence of the existence of E117 relies on observing a small number of decay events. There's plenty of interesting nuclear physics, including the discovery of a previously unknown isotope of lawrencium, but don't expect any chemistry for the foreseeable future.
Nevertheless, if I may be so bold allow me predict that E117 will be essentially entirely metallic with little to no halogen character. Its spin-orbit coupling will be so extreme that it will only be possible to describe it with a j-j like scheme, and as such it will have almost no similarity to the halogens fluorine through iodine. For more on this, see my posts on astatine, especially Astatine: Halogen or Metal? Part 3: Electronic Structure Calculations. Anything that applies to astatine will apply even more strongly to E117.
The scientists claim they discovered a four-quark particle, or tetraquark, composed of a charm, anti-charm, down, and an anti-up quark. The particle would appear to be roughly (or possibly even exactly) a bound state of two mesons, that is two pairs of color-anticolor quarks; for example red-antired and blue-antiblue. The charges of the charm and anti-charm obviously cancel, leaving -1⁄3 from the down and -2⁄3 from the anti-up, for a total charge of -1.
I can't speak to the quality of this research per se, but I do remember the excitement and subsequent let down over the pentaquark, so I'm going to wait to hear what the wider particle physics community concludes about this latest finding. Still, it's a pretty cool finding.
In the nonrelativistic quantum mechanics to which we are confining ourselves, electron spin must be introduced as an additional hypothesis.
Other undergraduate and graduate texts on quantum mechanics I have examined appear to take more or less the same view. But is it really true? Is it really impossible to justify spin without invoking relativity? In this post I plan to demonstrate that it is not. But first, a little background.
Background: The Discovery of Spin
In retrospect, spin was first discovered in 1922 by Otto Stern and Walther Gerlach, though they didn't realize it at the time. In the now famous Stern-Gerlach experiment, they found that an electron passing through a magnetic field will be deflected in one of two possible directions. (Historically, they found this to be true for gaseous silver atoms, but the reason was later established to be because of the spin of the single unpaired electron.)
RT @greatbritain: UK discovered more elements in periodic table than any other country pic.twitter.com/yjN2BQ3QWx #museumweek
— UKTI (@UKTI) March 27, 2014Overall I think it's a fascinating chart, but I do have a couple of problems with it. One, it lists element 117 as undiscovered, despite the fact that it was synthesized by a joint U.S.-Russian team in 2010. Still, element 117 hasn't been officially accepted by the IUPAC/IUPAP, so I suppose the creators are just playing it safe.
But more importantly, I feel the chart's creators err when they assign the discovery of oxygen to England and Sweden. For the historical record, Carl Wilhelm Scheele of Sweden in 1772 and Joseph Priestley of England in 1774 both independently isolated oxygen by heating HgO and the like. Although Scheele performed his experiment first, Priestley published first, so there's some question as to which one deserves more credit-this chart seems to split the difference.
The authors claim that "...there are, in fact, few parallels between lanthanide and actinide chemistry." The article continues that actinide chemistry (or californium-highly polarizable ligand chemistry, at any rate) in many respects is actually more similar to d-block behavior than expected f-block behavior.
What was particularly interesting was that the f-orbitals where also involved in bonding. The original article in Nature Chemistry discusses some DFT calculations on the californium borate, using a "60-electron core quasi-relativistic pseudopotential" for the californium. As far as I can tell, the authors where primarily concerned with scalar relativistic effects (i.e. s- and p-shell contraction and d- and f-shell expansion) rather than spin-orbit coupling. If so, the explanation for their results should be that the higher degree of s-orbital contraction in the actinides versus the lanthanides results in substantially larger f-orbitals, which are better able to form covalent bonds.
In any event, this article opens some interesting questions about heavy element chemistry, and I'm excited to seeing where it will lead.
For "Part 1: Background" click here. For "Part 2: Introduction to Relativistic Quantum Chemistry" click here.
In this post I will be applying the lessons of Part 2 on relativistic quantum chemistry to discuss papers which publish significant (relativistic) electronic structure calculations of astatine. To date, I have only found two which I would put in this category; they are referenced at the end of the paper. Articles of lesser direct significance will be referenced as they come up. I will attempt to keep this blog post updated as I become aware of other articles or as they are published. If anyone is aware of any relevant articles, I would greatly appreciate if you leave a reference or link in the comments below.
Note to readers: To date I have attempted to keep my posts approachable by non-chemists in an effort to provide chemical education to anyone interested. Due to the subject nature, this post will perforce be something of an exception and will contain parts that may be unaccessible to anyone without at least bachelor's level expertise in chemistry or physics. Nonetheless, I will attempt to make the conclusions accessible to a more general audience.
Before reviewing the book, a brief background on Primo Levi is necessary. Levi was born in 1919 into a relatively well-to-do Jewish family in the Piedmont region of northern Italy. His entry into university to study chemistry coincided with the increase in severity of the Fascist party's laws against Jews. As a result, Levi was among the last Jews able to earn a degree in Fascist Italy. Although racial laws should have prevented Levi from gaining employment as a chemist after graduation, through a combination of an Italian army officer who—in Levi's assessment—"took a bitter and subtle pleasure in breaking the laws of racial separation," and subsequent employment by a Swiss firm operating in Milan, Levi managed to work as a chemist through the partition of Italy in 1943.
The article discusses "psychonauts" who behave as human guinea pigs for novel, potentially physchotropic compounds (they aren't big believers in lab safety protocols). By slightly modifying known drugs and marketing them as not for human consumption, they can operate more or less inside the law for a few years until the government catches on. I won't attempt to rehash the entire article here, but I do want to point out the part that's of particular interest to me as a chemist.
The author invented a fake identity and UK based pharmaceutical company and set off searching for a contractor to synthesize a phenmetrazine like compound. After about a week he hired a Shanghai based company willing to synthesize the drug and ship in to the UK with minimal questions asked, all for only a few hundred dollars.
What really struck me was the degree of chemical expertise the Chinese company exhibited. They not only developed a synthesis route for the compound within two weeks, they then proceeded to use liquid chromatography to test its purity and even emailed an NMR spectrum of the drug before shipping. When the author received the compound, he sent it to a lab at Cardiff University, who confirmed its purity and the NMR spectrum. The Chinese company were legitimately highly trained and skilled chemists.
What's the take home message here? There will always be intelligent people willing to use their intelligence for bad (or at least morally grey) aims, and we as chemists have proven that we're no exception. Still, it hits home to see an example as blatant as this. I suppose this is how doctors feel when they read about other doctors selling narcotic prescriptions.
