Decay of Laser-Induced Excitations of<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>F</mml:mi></mml:math>Centers

Abstract

A strong population of excited $F$-center states is achieved in various alkali halides using a short intense pulse of a $Q$-switched ruby laser. During the presence of the excited $F$ centers the time dependence of their decay is measured with a fast-recording spectrometer. This is done by monitoring the absorption changes connected with the ground-state or excited-state populations. Using this method for crystals containing low $F$-center concentrations, the lifetime of the excited state of $F$ centers in KI, RbI, CsI, RbBr, and CsF is measured from 7 to about 80\ifmmode^\circ\else\textdegree\fi{}K by monitoring absorption changes in the region of the $\ensuremath{\beta}$, the ${\ensuremath{\beta}}^{*}$ and the $F$ band, respectively. For KI samples containing high $F$-center concentrations it is found that the decay curves are nonexponential.