Chad’s been busy blogging about his recent lab visits to NIST and U. Maryland, and the writeups are, as usual, top-notch. Cavity QED (a subfield I find fascinating and something I might have pursued had the right opportunities arisen when I was looking for a postdoc), Cold Plasmas, Biophysics (you might have a “what the?” reaction, but it uses optical tweezers, which is why this doesn’t really fall under “one of these things is not like the other,” Four-Wave Mixing (another field I find interesting, and the summary is definitely worth a read if you’ve ever wondered if things you learned in QM were ever actually applied to anything. You’ve got electrons moving between states without ever exciting the atom, and squeezed states, which is an exploitation of the Heisenberg Uncertainty Principle)
Last but not least one on this list (so far, anyway) is about trapping Francium. As I mentioned in the U.P. comments, I was a postdoc in the group that tried to trap Francium at TRIUMF several years back, and when we started discussing plans to do it, we were hoping to trap before the Stony Brook lab did so. Well, they succeeded while we … met some obstacles. As I recall, we weren’t the first in line to use the target; there was another experiment that went first, and so we only had a short time to try. And trying to trap something that has no stable isotopes is a special challenge. You have to reference your laser to something, so that you know he frequency of the light you are generating. With an existing stable isotope that’s straightforward, since you can use an absorption line, and the frequency of the radioactive isotope would be close by. Otherwise you do something like locking to an iodine transition, or some other reference cell used in spectroscopy. And you have to know the frequency you want to generate — with no stable or at least naturally-occurring isotopes the spectroscopy information would be very sparse in comparison to other alkalis, so your calculation of where you expect the transition to be has some uncertainties, meaning you have to search frequency-space until you find something. And we ran out of beam time before we saw anything.
And, as I had mentioned, we (well, someone at TRIUMF) got a call from a watchdog station that tries to detect nuclear fallout, wanting to double-check on things. They knew the signature they were reading wasn’t from a bomb, but they knew something was up and guessed our target material: Thorium. When you blast that with energetic protons, you get lots of heavy isotopes.