Resonance Raman Scattering from F_A(Li)-centers in KCl

Abstract

Raman scattering due to very small concentrations of point defects in crystals may become observable by using light for the excitation whose energy is close to some resonance energy of the defect system. This has been clearly demonstrated by Worlock and Porto₍₁₎ in their investigation of F-center Raman scattering in NaCl and KCl. We apply this method in a study of F_A(Li) centers in KCl. We expect to observe Raman spectra of those lattice vibrations which interact with the excited states of the defect ⁽²⁾. The presence of the defect in the crystal destroys the translation symmetry of the lattice and thereby makes one-phonon scattering allowed for certain types of perturbed lattice modes throughout the Brillouin zone. In the unperturbed NaCl structure one-phonon scattering processes are forbidden by symmetry and only a relatively weak two-phonon scattering is present.

Thiswork has been supported by the Committee for Institutional Funds, University of Utah and by AFOSR Contract #1141–66 (F. Lüty).