〈S z〉 wall relaxation measurements of optically pumped sodium atoms at high magnetic field

Abstract

The wall relaxation time for optically pumped 〈Sz〉 polarized sodium atoms colliding with copper, stainless-steel, and dry-film coated surfaces has been measured as a function of an applied magnetic field. Results show that the mean number of wall collisions increases from one to about four before depolarization of sodium atoms occurs on a copper wall in a high (12 kG) magnetic field, whereas the atoms relax after a single collision on a stainless-steel wall even in high fields. The relaxation time for a dry-film coated surface, for the cell geometries used in our work, is dominated by the effusion of polarized sodium atoms from the cell. Our measurements also allow an estimate of the strength of the local magnetic field causing the 〈Sz〉 depolarization and of the correlation time of the depolarization interaction on the surface. The importance of these experimental results as applied to the performance of optically pumped polarized ion sources is also discussed.