SELF-TRAPPED EXCITON IN LI2GEO3

Self-trapped excitons (STE) are discovered in Li:GeO3 crystal. The PL band at 2.7 eV with a strong Stoke's shift is excited in the intrinsic absorption range of Li2GeO3 crystal, in which the optical gap is situ ated at 6 eV. The activation energy of the STE luminescence thermal qu enching is not monoenergetic and is situated in the range 40-100 meV. The luminescence is strongly polarized. The decay kinetics can be char acterized by tau = 0.9 ms at 45 K. At 5 K it can be approximated by fa st (0.6 ms) and slow (4-2.5 ms) components. Decay kinetics is determin ed by triplet state of STE splits in zero magnetic field. Two differen t excited tripler states (centers) have the average ODMR parameters [D ] = 6.3 GHz and [E] = 0.6 GHz. The transient absorption of STE shows t wo bands at 3.7 and 4.7 eV, similar to transient absorption of STE in GeO2 crystal with the structure of alpha-quartz.