Electronic vibrational energy transfer between an F-center electron and the stretching mode of a neighboring OH- impurity was studied, for the case of F-OH- and F-OD- pairs, by means of Stokes and anti-Stokes resonant Raman scattering. Stepwise F  FH conversion experiments revealed the existence of several F-OH- aggregate centers with stretching-mode frequencies that were within about 10/cm of that of the undisturbed impurity ion. In particular, the stretching modes of the 2 bistable configurations of the FH(OH-) center were identified. Polarization data were unable to distinguish between parallel and perpendicular orientations of the impurity with respect to the FH defect axis in these configurations. The primary electronic vibrational transfer process for both isotopes was characterized by accurately measuring the excitation-power dependence of the populations of the vibrational levels. The effect of vibrational-vibrational transfer was negligible; as confirmed by varying the impurity concentration. By assuming that each excited FH electron transferred energy to the impurity vibration in its relaxation cycle, the vibrational lifetime of OD- and OH- in the FH center was estimated to be of the order of 100 and 10ns, respectively. The isotope effect, and its independence of temperature, suggested that decay into hindered rotations was the relaxation mechanism of the stretching vibration.

E.Gustin, M.Leblans, A.Bouwen, D.Schoemaker, F.Luty: Physical Review B, 1996, 54[10], 6963-76