Impurity core-valence transitions in Rb 1− xCs xCaCl 3 crystals

Abstract

The luminescence of Rb 1− x Cs x CaCl 3 crystals has been investigated using both pulsed X-ray excitation and pulsed synchrotron radiation. Intense emission bands at 4.6 and 3.9 eV in the transparency region of the crystal are ascribed to the impurity induced core-valence transitions (CVTs) of 5pCs 2+ → 3pCl − type. The luminescence excitation spectrum exhibits a threshold ( E t = 14.00 +0.05 eV) corresponding to the photon energy necessary to create holes in the 5pCs band. It is shown that two cations (Rb + and Cs +) with partially overlapping upper core bands take part in the excitation of impurity CVTs in the crystal. It has been found also that high energy excitation ( E > 25 eV) gives a reduced decay time of the luminescence ( τ = 2.45 ns) compared to the excitation at the core exciton peaks where τ = 2.84 ns.