Short-lived color and luminescence centers in LiNbO3 crystals irradiated by pulsed electron beams

Data on spectra of short-lived optical absorption (SLOA) and luminescence i nduced in congruent crystals of lithium niobate by a pulsed electron beam ( 0.25 MeV, 20 ns, 15-160 mJ/cm(2)) in a temperature range of 80 to 350 K are presented. Anisotropic bands with maxima at 1.6 and 4.0 eV, originating fr om the capture of one and two conduction electrons by an (Nb-Nb-Nb-Li) comp lex, respectively, and weakly polarized bands at 2.5 and 3.3 eV due to hole s located at Li and Nb vacancies are identified in the structure of SLOA sp ectra. Cathodoluminescence (CL) of lithium niobate crystals is characterize d by fast (tau < 4 ns) decay and a broad spectrum, which contains the same bands as the SLOA spectra. It is shown that the change in the initial amoun t of defects in reduced crystals at 830 K results in an identical change in both the CL and SLOA spectra. A model which treats the luminescence as the result of radiative nonphonon transitions that accompany the thermalizatio n of charge carriers captured into the ground state of a polaron is discuss ed. (C) 2001 MAIK "Nauka/Interperiodica".