« Class review — 1/27 | Main | Class Review — 2/3 »

February 01, 2005

Class Review — 2/1

Hi Class,

I was talking trash at the end of class today. In fact, the hyperfine ground state splitting is small compared with room temperature, so the two states will be equally occupied. We see this any time we do spectroscopy in a room temperature vapor cell! Most AMO experiments begin at temperatures below 1 mK, and then only the lower ground state is occupied. The lifetime of the upper ground state is very long, and we will estimate it when we talk about light interacting with atoms.

Here is a review of class today:

  1. Forget trying to calculate the electronic structure of real atoms. Screening is a serious effect in alkali atoms, for example. We use a semi-empirical formulation (quantum defect theory) for estimating quantities, and look up transition wavelengths in databases when we really care. The NIST database and the data from Dan Steck and Mike Gehm are valuable resources.

  2. Hyperfine structure comes from the interaction of the electron with the nuclear electric and magnetic moments. The hyperfine interactions are diagonal in the F=I+J basis, where F is the total angular momentum. So, we construct states as |F,mF>, which are superpositions of states in the |mI,mS> basis. The hyperfine splittings (ground and excited states) can be calculated using some formulas and the A and B constants, which are measured.

  3. Isotope shifts are important, since optical transitions can be different for different isotopes of the same atom. A big contributor to isotope shifts is the finite volume of the nucleus. I forgot to mention that there are other effects, such as effects due to the internal structure of the nucleus (non-uniform charge and current distributions).

These reviews will soon appear on a blog that I am starting for the class. You will be able to leave comments on the lectures and use it as a discussion board. More information to follow!

Brian

Posted by Brian at February 1, 2005 02:30 PM

Comments

Post a comment

Thanks for signing in, . Now you can comment. (sign out)

(If you haven't left a comment here before, you may need to be approved by the site owner before your comment will appear. Until then, it won't appear on the entry. Thanks for waiting.)


Remember me?