Noble-Gas-Induced Rubidium Spin Disorientation

Abstract

Cross sections for noble-gas-induced Rb spin disorientation are calculated, taking into account second-order cross terms in the spin-orbit and K·L couplings, as initially proposed by Bernheim. Contrary to Bernheim, it is argued that spin-orbit effects are negligible in first order. Using simple wave functions, it is shown that the spin-orbit coupling provided by the electric field of the Rb ionic core, when the valence electronic orbital is deformed in short-range encounters, is sufficient to yield the observed relaxation rates. For He, the calculated disorientation cross section shows agreement to within a factor of 6 with the experimentally determined cross section for depolarization of optically oriented Rb vapor. Moreover, if, for all Rb-rare-gas pairs, we assume the same proportionality between the short- and calculated long-range energies at the kinetic radius, agreement to within a factor of 6 for Ne, A, Kr and Xe is also obtained.