Relaxation of OH−Dipoles in KCl at Low Temperatures

Abstract

The direct and Raman relaxation rates of O${\mathrm{H}}^{-}$ electric dipoles in KCl are computed using a point-charge—point-dipole model in which we allow for the possibility that the equilibrium position of the dipole is displaced from the center of octahedral symmetry. This model can thus include the effect of an O${\mathrm{H}}^{-}$ quadrupole moment. Such a moment can be represented by an effective displacement of the dipole. Estimates are made of the rates at temperatures between 2 and 11°K in the presence of weak and strong dc electric fields parallel to the [001] or [111] axis. Our estimates are in good agreement with the value measured by Feher, Shepherd, and Shore at 11°K. Agreement with the rate measured by Bron and Dreyfus at 1.4°K is obtained by allowing for an effective displacement of the dipole equilibrium position from a centrosymmetric position. The Raman transitions are shown to be strongly temperature-dependent, dominating the dipole-lattice relaxation processes at very low temperatures, while the direct transitions display a linear temperature dependence.