Atoms and Molecules

Category archives for Atoms and Molecules

Laser-Cooled Atoms: Francium

Element: Francium (Fr) Atomic Number: 87 Mass: Numerous isotopes ranging in mass from 199 amu to 232 amu, none of them stable. The only ones laser cooled are the five between 208 amu and 212 amu, plus the one at 221 amu. Laser cooling wavelength: 718 nm Doppler cooling limit: 182 μK. Chemical classification: Alkali…

Laser-Cooled Atoms: Strontium

Element: Strontium (Sr) Atomic Number: 38 Mass: Four stable isotopes, ranging from 84 to 88 amu Laser cooling wavelength: Two different transitions are used in the laser cooling of strontium: a blue line at 461 nm that’s an ordinary sort of transition, and an exceptionally narrow “intercombination” line at 689 nm. Doppler cooling limit: 770…

Spooky Action at What Distance?

When I wrote up the giant interferometer experiment at Stanford, I noted that they’ve managed to create a situation where the wavefunction of the atoms passing through their interferometer contains two peaks separated by almost a centimeter and a half. This isn’t two clouds of atoms each definitely in a particular position, mind, this is…

Laser-Cooled Atoms: Xenon

Element: Xenon (Xe) Atomic Number: 54 Mass: nine “stable” isotopes, masses from 124 to 136 amu. Xenon-136 is technically radioactive, but with a half-life of a hundred billion billion years, so, you know, it’s pretty much stable. Laser cooling wavelength: 882 nm Doppler cooling limit: 120 μK Chemical classification: Noble gas, part of column VIII…

Laser-Cooled Atoms: Helium

Element: Helium (He) Atomic Number: 2 Mass: two stable isotopes, 3 and 4 amu. Laser cooling wavelength: 1083 nm Doppler cooling limit: 38 μK (It should be noted, though, that despite the low temperature, laser-cooled helium has a relatively high velocity– that Doppler limit corresponds to an average velocity that’s just about the same as…

A little over a year ago, I visited Mark Kasevich’s labs at Stanford, and wrote up a paper proposing to use a 10-m atom interferometer to test general relativity. Now, that sounds crazy, but I saw the actual tower when I visited, so it wasn’t complete nonsense. And this week, they have a new paper…

Laser-Cooled Atoms: Rubidium

Element: Rubidium (Rb) Atomic Number: 37 Mass: two “stable” isotopes, 85 and 87 amu (rubidium-87 is technically radioactive, but it’s half-life is 48 billion years, so it might as well be stable for atomic physics purposes. Laser cooling wavelength: 780 nm Doppler cooling limit: 140 μK Chemical classification: Alkali metal, column I of the periodic…

Laser-Cooled Atoms: Sodium

Element: Sodium (Na) Atomic Number: 11 Mass: one stable isotope, 23 amu Laser cooling wavelength: 589 nm Doppler cooling limit: 240 μK Chemical classification: Alkali metal, column I of the periodic table. Like the majority of elements, it’s a greyish metal at room temperature. Like the other alkalis, it’s highly reactive, and bursts into flame…

Know Your Laser-Cooled Atoms

At the tail end of the cold-atom toolbox series, I joked about doing a “trading card” version shortening the posts to a more web-friendly length. In idly thinking about this, though, it occurred to me that if one were going to have cold-atom trading cards, it might make more sense to have them for the…

This is probably the last trip into the cold atom toolbox, unless I think of something else while I’m writing it. But don’t make the mistake of assuming it’s an afterthought– far from it. In some ways, today’s topic is the most important, because it covers the ways that we study the atoms once we…