Zeeman Effect
The Zeeman effect lab is currently a work in progress, and thus I won't say too much about it. The basic idea is this. If you put an atom in a magnetic field it's energy states will split into a number of different components. This is an extremely small effect, though you can make it stronger by increasing the magnetic field you put the field in.
Somehow this experiment will measure this energy level splitting, probably by observing spectral lines because, as has been remarked elsewhere (though not by me), Ken loves spectroscopy.