A spin-polarized He (2³S₁) metastable atom source for surface research
Walters, G. King
Master of Arts
Surface science has a paucity of probes, particularly for spin-dependent studies. This thesis describes a 2 3S1 He probe, recently developed in this laboratory, that can be used for such investigations. There are three interaction mechanisms such a probe can undergo: resonance ionization/ Auger neutralization, Auger deexcitation, or surface Penning ionization. All are discussed and compared. The important concepts introduced include electronic transitions, factors affecting the interactions, variation of atomic energy levels, and the convolution problem. After introducing these concepts, and describing the resulting physical phenomena, the experimental apparatus is examined. The thesis delineates the rationale for a multi-chamber design and the problems encountered. One diagnostic, a Stern-Gerlach magnet used as a polarization analyzer, is particularly useful and is described in detail. By using the analyzer, we found the beam is approximately 5 percent polarized. Finally, several problems related to the first experiments are discussed.