Auger-free luminescence due to interatomic p-d transition and self-trapped exciton luminescence in Rb _2ZnCl _4 crystals

摘要

It is reported that Auger-free (AF) luminescence appears with two bands at 4.5 and 6.3 eV in Rb _2ZnCl _4. This luminescence originates from a radiative transition of the Cl 3p valence electrons into the Zn 3d outermost-core holes. The present work is the first observation of AF luminescence due to interatomic p-d transitions in halide crystals. The appearance of two AF luminescence bands suggests the existence of two types of AF transitions following core hole creation. A largely Stokes-shifted luminescence band is also found to appear at 1.9 eV. This band has an excitation threshold at the fundamental absorption edge, and is ascribed to the radiative decay of a self-trapped exciton.