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Multiplication mechanisms of electronic excitations in KBr and KBr:Tl crystals
Phys. Rev. B 50, 6500(R) – Published 1 September, 1994
DOI: https://doi.org/10.1103/PhysRevB.50.6500
Abstract
The reflection spectrum and excitation spectra of self-trapped exciton emissions have been measured in the spectral region from 6.5 to 30 eV for a freshly cleaved KBr crystal at liquid-helium temperature. The following mechanisms of multiplication of electronic excitations have been distinguished by using luminescence methods: (i) formation of secondary excitons by hot photoelectrons; (ii) formation of secondary electron-hole pairs by hot photoelectrons; (iii) formation of electron-hole pairs due to nonradiative Auger decay of cation electronic excitations. The analysis of the spectrum of the intensity ratio of π and σ emissions of self-trapped excitons allowed us to obtain quantitative data on exciton formation by photoelectrons. The excitation spectra for the T and X Jahn-Teller components of -center emission have been measured in a KBr:Tl crystal at liquid-helium temperature in the region from 6.5 to 30 eV. A sharp maximum at 15 eV in the intensity ratio of T and X emissions is connected with the excitation of centers by hot photoelectrons.
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