Resonance electronic Raman scattering in erbium phosphate crystals

Abstract
Resonance enhancement factors of 10 to 100 have been observed for the electronic Raman scattering transitions in crystals of pure ErPO4 and 1% Er3+ diluted in LuPO4. The resonances were excited by the 488.0-nm line of an argon-ion laser. This line is nearly coincident with the crystal-field levels of the 4F7/2 multiplet of Er3+. The differences in relative intensities between the transitions in ErPO4 and those in 1% Er3+ in LuPO4 arise from shifts in the energy levels in the two systems and suggest that quantum-mechanical interference effects play an important role.