Category: Optics

Laser-Cooled Atoms: Chromium

L to R: Shiny chromium bits, laser tables for the chromium trap in Paris, and an electron shell diagram.

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.… Continue reading Laser-Cooled Atoms: Chromium

Laser-Cooled Atoms: Lithium

L to R, lithium metal in paraffin, the red light for cooling lithium (from the LaserFest web site), and an electron shell diagram from wikimedia.

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… Continue reading Laser-Cooled Atoms: Lithium

Laser-Cooled Atoms: Francium

L to R, a schematic of the accelerator used to make francium, a cartoons of a system with an anapole moment (both take from the William and Mary group), and an electron shell diagram for francium from Wikimedia.

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… Continue reading Laser-Cooled Atoms: Francium

Laser-Cooled Atoms: Strontium

L to R, strontium crystals, images of BEC in strontium, and an electron shell diagram (which, like the crystals, is from Wikimedia).

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… Continue reading Laser-Cooled Atoms: Strontium

Laser-Cooled Atoms: Xenon

L to R, a comic cover from the comic bok periodic table, a graph from my Ph. D. thesis, and an electron shell diagram from Wikipedia.

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… Continue reading Laser-Cooled Atoms: Xenon

Laser-Cooled Atoms: Helium

L to R, an image from Up (taken from this blog post), the helium trap at the University of Amsterdam, and an electron shell diagram of He from Wikimedia.

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… Continue reading Laser-Cooled Atoms: Helium

Laser-Cooled Atoms: Rubidium

L to R: Rubidium metal, the first Rb BEC, and an electron shell diagram of Rb. Images from wikimedia and NIST.

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… Continue reading Laser-Cooled Atoms: Rubidium

Know Your Laser-Cooled Atoms

A somewhat outdated slide highlighting elements that have been laser cooled.

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… Continue reading Know Your Laser-Cooled Atoms

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

Sample images with and without atoms, and the subtracted image used to study BEC. From an old talk.

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… Continue reading Tools of the Cold-Atom Trade: Atom Detection and Imaging

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

Kris Helmerson of NIST looking into the vacuum chamber at a sodium MOT.

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?… Continue reading Tools of the Cold-Atom Trade: Magneto-Optical Traps