Level mixing and anisotropy effect in resonant Raman electron paramagnetic transitions in ruby forBperpendicular toc

Abstract

Doubly resonant Raman electron paramagnetic transitions in ruby (Al${}_{2}$O${}_{3}$:Cr${}^{3+}$) have been investigated using dye laser excitation tuned across the range of the Zeeman components of its well-known ${R}_{1}$ emission line. With magnetic field B normal to c, the optic axis of ruby, it is seen that the Raman electron paramagnetic resonance (EPR) lines exhibit significant intensity enhancements due to the simultaneous occurrence of ``in resonance'' and ``out resonance,'' as visualized in the Kramers-Heisenberg formalism of inelastic light scattering. The specific Raman EPR features observed in the present study, together with their resonances, however, differ markedly from those observed in our previous investigation with $\mathbf{B}\ensuremath{\parallel}\mathbf{c}$. These differences can be traced to level mixing effects within the Zeeman multiplet of the ${}^{4}{A}_{2}$ (ground) state on the one hand, and the negligible value of ${g}_{\ensuremath{\perp}}$ for the $\mathrm{E\ifmmode \bar{}\else \={}\fi{}}$ (excited) state of the ${R}_{1}$ emission line on the other. Furthermore, we note that with B\ensuremath{\perp}c and under resonant conditions, the experimentally observed \ensuremath{\Delta}$m$ $=$ \ifmmode\pm\else\textpm\fi{}1 pair of Stokes and anti-Stokes Raman lines are not connected by time-reversal symmetry.