Stress-Induced Dichroism and Energy Shifts in theA,B, andCAbsorption Bands in KCl: Tl

Abstract

The effects of uniaxial stress on the $A$, $B$, and $C$ absorption bands of KCl: Tl are determined using a static and dynamic Jahn-Teller interaction. The uniaxial stress alters the local symmetry giving rise to preferred spacial directions which, in turn, causes dichroism in the observed absorption spectra. The dynamic interaction accounts for the time-average splitting of energy levels which manifests itself by causing shifts in the band peaks. A calculation of the polarization effects and the shifting of the energy levels is carried out for the cases of [001] and [110] uniaxial stress. This is accomplished by (a) determining the transition probabilities for transitions from the $6{s}^{2}$ ground state to the $6s6p$ excited state of ${\mathrm{Tl}}^{+}$ in both ${D}_{4h}(001)$ and ${D}_{2h}(110)$ environments and (b) determining the excited-state eigenenergies in terms of the interaction modes characterized by the above symmetries. The results are shown to compare favorably with recent available experimental results. Several theoretical conclusions are reached which await experimental verification.