Measurement of Debye-Waller factors by Raman scattering from inter-term excitons and exciton-multiphonon states in FeF₂

We have observed inter-term Raman scattering from 5T2g→5Eg Frenkel excitons in antiferromagnetic FeF2. It differs qualitatively from previously observed intra-term scattering in a sharply reduced zero-phonon cross section and the appearance of relatively strong exciton-phonon scattering. Since the Raman process is fully allowed, it is possible to measure excited state Debye-Waller factors, D, and we find D(Λ3+ + Λ4+, 5Eg) = 0.04 and D(Λ1+, 5Eg) = 0.03. © 1974.