Temperature dependence of the electron--rubidium spin-exchange cross section

A spin-exchange optical-pumping experiment to study the temperature dependence of the electron-rubidium spin-exchange cross section is reported. In this experiment, electrons were polarized in a weak magnetic field by spin-exchange collisions with optically pumped Rb atoms. The electron-Rb collisions were the principal source of the electron-spin-resonance linewidth, and they also produced a shift in the resonance frequency. The magnitudes of the linewidth and frequency shift are functions of the electron-Rb-scattering phase shifts. The electron linewidth at fixed Rb density was essentially constant over the temperature range 200-840 °K indicating the spin-exchange cross section is well approximated by a 1/v velocity dependence. The ratio of the frequency shift to linewidth was 0.075±0.005 at 300 °K with an estimated Rb polarization of (20±10)%, and the ratio was 0.027±0.007 at 600 °K with a Rb polarization of (10±5)%.