The distribution of the eigenvalues of differential operators in large domains

Abstract

The excitation spectra for intrinsic luminescence due to recombination of selftrapped excitons at liquid helium temperature have been measured in NaC1, NaBr, RbCl and RbBr. The observed sequence of thresholds is explained in terms of multi-exciton production processes involving both valence and core excitons. Results are compared with published optical and photoelectron data and found to be in reasonable accord.