A luminescence spectroscopy study of SrI2:Nd3+ single crystals

The paper presents the results of a study on the luminescence of SrI2:Nd3+ single crystals grown by the vertical Bridgman method. The photoluminescence (PL) spectra of SrI2:Nd crystals show characteristic lines corresponding to transitions in trivalent Nd3+ ions, the most intense line at ca. 1070 nm is due to the radiative F3/24→I11/24 transitions. Efficient PL excitation in a crystal transparency band occurs due to optical 4f−4f transitions from the ground 4I9/2 state, or the charge transfer transitions I−→Nd3+. The paper discussed two new PL emission bands at 2.8 and 3.8 eV, associated with the lattice defects formed in SrI2 crystal at introducing Nd3+ impurity ions; two intense narrow PL excitation bands at 5.52 and 5.31 eV, originating from free and defect-bound excitons, respectively; an efficient channel of exciton energy transfer between the host lattice and defects. We calculated the H(k) functions of distribution of the elementary relaxations over the reaction rate constants and explained on this basis the nonexponential PL decay kinetics in SrI2:Nd3+ crystal.