Color Center Studies in Alkali Halides by Pulsed Electron Beam Irradiation

Abstract

The formation and decay of color centers in alkali halides have been studied using a pulsed electron beam. The F and V -type bands reach maximum heights in optical density at the end of the radiation pulse. V _k and V ₁ bands in KBr appear to show the first order decay kinetics; their room temperature life times are 1.3 and 3.8 µsec, respectively. A fraction of F and F ' bands bleach by the annihilation with migrating V _k centers. The activation energies for the disappearance of H , V ₁ and V _k centers in KBr are found to be 0.09, 0.25 and 0.39±0.02 eV, respectively. A fraction of H centers in KCl decays with a temperature independent time constant (∼0.13 µsec) which is due to the tunneling with nearby F centers. In crystals containing U -centers (H ^- ions) the F band continues to grow for several microseconds after the pulse. Absorption bands which decay with the same time constant as the F band growth have been found at 775 mµ (KBr) and 725 mµ (KCl).