Intensities and asymmetries of electronic Raman scattering in Thulium and Erbium phosphate

An investigation of the low-temperature electronic Raman scattering spectra of ErPO₄ and TmPO₄ has been carried out. The experimental intensities have been compared with the standard second-order theory of two-photon processes for both intermultiplet and intramultiplet transitions between individual crystal-field levels. Adequate agreement is found in the case of ErPO₄, but serious discrepancies exist for TmPO₄. It is shown that electronic Raman scattering is a sensitive technique for testing the Judd-Ofelt–type theories of two-photon processes in rare-earth crystals. Strong asymmetry, a characteristic feature of electronic Raman scattering, has been observed in several of the transitions.