Polarized electrons from penning ionization in a flowing helium afterglow
O'Neill, Malcolm Ross, 1940-
Walters, G. King
Master of Arts
An experimental apparatus is described which provides a spatial decay of the excited species from a helium discharge. This "flowing afterglow" has been constructed and the helium metastable atoms He(23S1) are seen to decay over a distance of approximately 30 cm at a helium flow, rate which produces a pressure of 0.1 Torr in the afterglow. The He(23S1) atoms can be polarized using a high intensity helium lamp which produces circularly polarized light. The light propagates in the direction of a weak magnetic field which produces Zeeman splitting of the energy states of the metastable atom. Polarizations of the metastables reach 60 percent. The thesis describes the production of polarized electrons from Penning reactions between polarized metastables (mj = +1) and impurities (mj = 0), A detectable electron polarization will lend credence to the Wigner spin rule and make possible a study of the spin dependence of Penning ionization reactions. Extraction of electrons from the afterglow and analysis by the techniques of high energy Mott scattering are also described. No electron polarization measurements have yet been made due to difficulties in extracting and collimating the electron beam.