Emission spectra of xenon impurity states in solid and liquid krypton

In this paper we present the results of an experimental study of electronic energy transfer in xenon-krypton liquid and solid alloys. The α-induced luminescence of these dense systems consists of three emission bands which are assigned to the host Kr*2 molecule, the guest XeKr*heteronuclear molecules, and the Xe₂*homonuclear molecule. Electronic energy transfer occurs via dipole-dipole coupling between Kr₂*and Xe single impurity states in the liquid and in the solid as well as to impurity aggregates in the solid. The critical radii for energy transfer were evaluated as R_q = 25 Å in the solid at 110 °K and estimated to be R_q ≃ 24 Å in the liquid at 120°K, while the second order perturbation theory results in the values R_q = 15 Å for the solid and R_q = 21 Å for the liquid. A dramatic decrease of the efficiency and energy transfer with decreasing temperature was observed, which is consistent with the proposed energy transfer mechanism. Some information regarding diffusion controlled reactions in liquid rare gases is reported.