Category: Experiment

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

Laser-Cooled Atoms: Sodium

L to R, sodim metal, sodium optical molasses, and an electron shell diagram of sodium. Images from Wikimedia/ NIST.

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… Continue reading Laser-Cooled Atoms: Sodium

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A somewhat outdated slide highlighting elements that have been laser cooled.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

The signature image of a cloud of rubidium atoms crossing the BEC transition, from the Nobel Prize site.

In our last installment of the cold-atom toolbox series, we talked about why you need magnetic traps to get to really ultra-cold samples– because the light scattering involved in laser cooling limits you to a temperature that’s too high for making Bose-Einstein condensation (BEC). This time out, we’ll talk about how you actually get to… Continue reading Tools of the Cold-Atom Trade: Evaporative Cooling

Tools of the Cold-Atom Trade: Magnetic Traps

Eric Cornell and Carl Wieman next to the original BEC apparatus, from http://www2.physics.utu.fi/projects/kurssit/FFYS4497/bec/H1-CarlWieman-EricCornell.gif

We’re getting toward the end of the cold-atom technologies in my original list, but that doesn’t mean we’re scraping the bottom of the barrel. On the contrary, the remaining tools are among the most important for producing and studying truly ultra-cold atoms. Wait, isn’t what we’ve been talking about cold enough? There is, as always,… Continue reading Tools of the Cold-Atom Trade: Magnetic Traps

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

Tools of the Cold-Atom Trade: Optical Pumping and Sisyphus Cooling

Sisyphus picture from http://ssifo.blogspot.com/

This topic is an addition to the original list in the introductory post for the series, because I had thought I could deal with it in one of the other entries. Really, though, it deserves its own installment because of its important role in the history of laser cooling. Laser cooling would not be as… Continue reading Tools of the Cold-Atom Trade: Optical Pumping and Sisyphus Cooling

Why Do Small Science?

Title slide from an overview talk about AMO physics, slides available at http://www.slideshare.net/orzelc/whats-so-interesting-about-amo-phyiscs

I spent an hour or so on Skype with a former student on Tuesday, talking about how physics is done in the CMS collaboration at the Large Hadron Collider. It’s always fascinating to get a look at a completely different way of doing science– as I said when I explained my questions, the longest author… Continue reading Why Do Small Science?

Tools of the Cold-Atom Trade: Optical Lattices

The famous optical lattice potential picture, from the Rolston group web site (http://www.physics.umd.edu/rgroups/amo/rolstonwebsite/bec.htm )

Last time in our trip through the cold-atom toolbox, we talked about light shifts, where the interaction with a laser changes the internal energy states of an atom in a way that can produce forces on those atoms. This allows the creation of “dipole traps” where cold atoms are held in the focus of a… Continue reading Tools of the Cold-Atom Trade: Optical Lattices