Laser cooling, varying magnetic field.

[sc86]

Okay, I have been reading the article Laser Deceleration of an Atomic Beam by William D. Phillips see attachment.
But I have a few problems:

1. Optical Pumping.
On page 1, 2. column they write:

The field both Zeeman tunes the decelerating atoms into constant resonance with the fixed frequency cooling laser and produces selection rules and Zeeman shifts that strongly discriminate against optical pumping.

I don't quite get the last part. How can the Zeeman effect change the selection rules?

2. Messurement of the velocity.
They decribe how they get the signals A (cooled atoms) and B (not cooled atoms), but how do the analysing laser work, when it messures the fluorescence?
And how is this fluorescence related to the velocity?

Hope some of you can give me a helping hand here.
/Stefan

 

[Redbelly98]

I don't quite get the last part. How can the Zeeman effect change the selection rules?

This is a homework problem?

I'm not entirely sure about the "field produces selection rules" part, it has been over 10 years since I worked in this area. It might help to know what F is for the unused hyperfine ground state (the one for which there is concern about being optically pumped into). Do you know F for this state?

 

[Redbelly98]

They decribe how they get the signals A (cooled atoms) and B (not cooled atoms), but how do the analysing laser work, when it messures the fluorescence?

In Fig. 1, it appears that a lens is used to take the fluorescence (spontaneously emitted light, due to excitation by the analysing laser) and focus it onto a photodetector of some kind.

And how is this fluorescence related to the velocity?

It is related to the Doppler shift.