F-Center Formation at Highly Excited Triplet States of Self-Trapped Excitons in KCl

Measurements have been made of the creation of the F centers by the optical excitation of the self-trapped excitons with a light pulse from a tunable dye laser. It is found that the ratio of the F -center concentration created by the light pulse to the triplet exciton concentration at the incidence of the light pulse depends on the integrated photon flux \(\varPhi\) as \(a\{1-\exp(-b\varPhi)\}\), where a and b are constants. Kinetic models are developed for treating the non-radiative processes of the highly excited self-trapped exciton, and the efficiency of the F -center creation from the highly excited triplet exciton was determined using the experimentally obtained parameters a and b . It is found that the efficiency is almost constant between 1.77 and 2.08 eV above the lowest triplet exciton and becomes higher above 2.58 eV. The dependence of the efficiency on energy is discussed in terms of existing models of the defect formation.