Relaxation and interaction of electronic excitations induced by intense ultra short light pulses in BaF 2 scintillator

Abstract

ABSTRACT Self-quenching in the decay characteristic s of self-trapped exciton (STE) lumine scence and cross-luminescence (CL) in BaF 2 were investigated under excitation with intense, ultra-short VUV-FEL pulses at free electron laser FLASH. The peculiarities revealed in emission spectra and decay kinetics at room and liquid helium temperature were discussed. Model calculations were performed to analyze the underlying processes in detail. Keywords: Self-quenching, ultrafast processes, barium fluoride, free electron laser, self-trapped exciton luminescence and cross-luminescence 1. INTRODUCTION Excitation density effects have a pronounced influence on relaxation processes in solids. They come into play in scintil-lating and dosimetric materials exposed to ionizing radiation or in laser materials operating in intense ultraviolet light fields. The scientific understanding of th e underlying process is poor, mainly becau se most of the studies of light emit-ting materials under short wavelength excitation have been pe rformed at weak and moderate excitation intensities due to limited availability of powerful light sources. Disembodied data on excitation density effects have been reported for wide-gap dielectrics studied by luminescence spectroscopy, by using such exc itation sources as powerful ion beams,