Excitation profiles of resonance electronic Raman scattering in ErPO4 crystals.

Abstract

The intensities of electronic Raman-scattering transitions between the ground and excited crystal-field states of the ground $^{4}\mathrm{I}_{15/2}$ multiplet of ${\mathrm{Er}}^{3+}$ in crystals ${\mathrm{ErPO}}_{4}$ were measured as a function of excitation frequency in the region of an intermediate-state resonance between the $^{4}\mathrm{I}_{15/2}$ ground state and a crystal-field state of the $^{4}\mathrm{F}_{7/2}$ multiplet. It is shown that for excitation frequencies near the intermediate-state resonance, the observed spectra are the result of electronic Raman scattering and are not due to absorption followed by fluorescence. No such determination could be made for direct resonance excitation. Enhancements of the intensities of the electronic Raman scattering by a factor on the order of 100 are reported. The electronic Raman-scattering excitation profiles (excitation frequency versus enhancement) are found to be asymmetric in excitation frequency about the resonance. These profiles can be accurately modeled using standard electronic Raman intensity theory and the measured oscillator strengths and linewidths of the $^{4}\mathrm{I}_{15/2}$${\ensuremath{\rightarrow}}^{4}$${\mathrm{F}}_{7/12}$ one photon transitions.