Theory of Spin Exchange between Optically Pumped Rubidium and Foreign Gas Nuclei

Abstract

Cross sections for spin exchange between alkali valence electrons and foreign nuclei in collisions of atomic Rb with atomic He, Ne, Kr, and molecular hydrogen are calculated. It is concluded that while classical dipolar hyperfine interactions are negligible, scalar interaction strengths are greatly magnified as a result of electron exchange. Specifically, it is shown that cross sections associated with the latter are as much as ${10}^5$ times those calculated if exchange effects are neglected. For ${\mathrm{He}}^3$, ${\mathrm{Ne}}^{21}$, ${\mathrm{Kr}}^{83}$, ${\mathrm{H}}_2$, and ${\mathrm{D}}_2$, the estimated cross sections for mutual spin flip are 1.1×${10}^{-24\mathrm{}}$, 1.0×${10}^{-23\mathrm{}}$, 1.0×${10}^{-22\mathrm{}}$, 3.6×${10}^{-25\mathrm{}}$, and 5.5×${10}^{-26\mathrm{}}$ ${\mathrm{cm}}^2$. For ${\mathrm{He}}^3$ and ${\mathrm{Ne}}^{21}$, these are comparable in magnitude to the corresponding experimental cross sections for the deplorization of optically oriented Rb. For the other gases considered, they are relatively much smaller, however. Cross sections for Rb electronic spin disorientation through spin-orbit interactions in collisions with molecular hydrogen are also calculated. They are considerably larger than those observed for the disorientation of optically pumped Rb vapor.