Laser-Cooled Atoms: Chromium

Element: Chromium (Cr) Atomic Number: 24 Mass: Four “stable” isotopes between 50 and 54 amu. Chromium-50 is technically radioactive, with a half-life considerably longer than the age of the universe, so… Laser cooling wavelength: 425nm, but see below. Doppler cooling limit: 120 μK. Chemical classification: Transition metal, smack in the middle of the periodic table. […]

Laser-Cooled Atoms: Lithium

Element: Lithium (Li) Atomic Number: 3 Mass: Two stable isotopes, masses 6 and 7 amu Laser cooling wavelength: 671 nm Doppler cooling limit: 140 μK. Chemical classification: Alkali metal, column I in the periodic table. Yet another greyish metal. We’re almost done with alkalis, I promise. Less reactive than any of the others, so the […]

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 […]

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 […]

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 […]

Tools of the Cold-Atom Trade: Atom Detection and Imaging

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 […]

Tools of the Cold-Atom Trade: Magneto-Optical Traps

Today’s dip into the cold-atom toolbox is to explain the real workhorse of cold-atom physics, the magneto-optical trap. This is the technology that really makes laser cooling useful, by letting you collect massive numbers of atoms at very low temperatures and moderate density. Wait a minute, I thought we already had that, with optical molasses? […]