Optical excitation of the two electronic absorption bands of F-centerCN- defect pairs in CsCl creates a highly efficient electronic to vibrational (e-v) energy transfer process, characterized by rapid nonradiative relaxation of the F electron in contrast to a slowly cascading sequence of fluorescence transitions between the six lowest excited CN- vibrational states. This behavior allows, by pumping with the same laser beam, to both populate nonequilibrium CN- vibrational states and to probe their existence and physical properties by anti-Stokes resonance Raman scattering. Experiments with this technique were performed, testing the temperature, wavelength, and intensity dependence of the anti-Stokes Raman spectra and their polarization. Comparison with the earlier vibrational emission results show close agreement for low-CN - doped crystals, but pronounced differences for higher-doped crystals, in which vibrational (v-v) energy transfer from the FH(CN-) centers into the free CN- defect system occurs. These results provide the basis for using pulsed anti-Stokes Raman spectroscopy as a viable probe for our planned time-resolution studies of the e-v and v-v transfer in these systems.
ASJC Scopus subject areas
- Condensed Matter Physics