Exciton kinetics in xenon–krypton cryocrystals

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Abstract
On the basis of experimental studies of the luminescence of Xe–Kr solid solutions under electronic excitation as well as on the basis of an analysis of the results within the framework of the model of diffusion motion in Xe–Kr solid solutions, we examine the mechanisms of the migration and relaxation of electronic excitations of the matrix and also study the processes of energy transfer to the impurity states of K and Xe2. It is shown that in pure Kr crystals and low-concentration solutions (c < 0.1 mole % Xe) the migration of excitations is due mainly to the diffusion of free excitons. The presence of a homological Xe impurity sharply increases the scattering of coherent excitations, which leads to self-trapping of the excitations. For c > 0.3% Xe as a result of this process energy transfer is affected primarily by self-trapped excitons. The agreement between the model diffusion calculations with the experimental data enabled us to determine the principal kinetic parameters of the motion of self-trapped excitons, viz., the diffusion coefficient, the average velocity, and the diffusion length of the exciton displacement.

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