Abstract
The emission and absorption of ${F}_{A}$(Li) centers in mixed crystals of KCl and KBr have been studied from 1.6 to 100 K at atmospheric and high pressures. While only one pair, ${F}_{A1}$ and ${F}_{A2}$, of absorption bands is observed, two types of emission bands, type I and type II, are obtained. The relative intensities of the type-I and type-II emissions depend both on the composition of the solid solution and on temperature. A possible formation mechanism of two relaxed excited states in a complete solid solution is discussed. The energy separation and intensity of the ${F}_{A}$ absorption band (${F}_{A1}$ and ${F}_{A2}$) in the ${\mathrm{KCl}}_{1\mathrm{\ensuremath{-}}\mathrm{x}}$${\mathrm{Br}}_{\mathrm{x}}$:Li system are observed under various pressures. Information about the off-center behavior in the mixed crystals is obtained from the pressure dependence of the separation between ${F}_{A1}$ and ${F}_{A2}$ absorption. The pressure variation of intensity in type-I and type-II emissions is also measured. These results show a different pressure effect on the relaxation processes of the two types of emission: the type-II emission is scarcely affected by the applied pressure contrary to a considerable pressure-induced nonradiative transition in the type-I emission. This situation leads us to investigate the relaxation process of the type-II emission under hydrostatic pressure.
Published Version
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