High-energy electronic excitations and radiation defects in SrCl2 crystals

Abstract

The electronic energy bands of the crystal SrCl2 have been evaluated on the projector augmented waves (PAW) basis using the ABINIT software package. The calculations were performed within the three approaches. The band gap obtained in the local density approximation (LDA) is much smaller than the experimental value. The value of derived by means of the Green’s function (GW) approach is close to the experimental one. The imaginary part of dielectric constant evaluated by means of the Bethe–Salpeter equation (BSE) shows the first excitonic peak, which agrees well with the experimental data. The luminescence excitation and emission spectra as well as luminescence kinetics of SrCl2 single crystals were investigated at 10 K using the vacuum ultraviolet (VUV) synchrotron radiation. There were found three main emission bands of SrCl2 crystals located at 247, 304 and 401 nm associated with direct and indirect exciton transitions at different points in the Brillouin band of the SrCl2 matrix and the corresponding excitation bands located at 7.99 ± 0.01 and 7.40 ± 0.01 eV.The emission of the triplet self-trapped excitons peaked at 405 nm was investigated in undoped single SrCl2 crystals under the x-ray radiation in the 80–297 K temperature range. It was shown that there is a high probability of non-radiative decay of self-trapped excitons into genetic pairs of (Vkα − F*)-centers, which at 80 K cause long phosphorescence of the samples irradiated by x-rays as well as produce the main thermally stimulated luminescence peak at 134 K.