Low-temperature time-resolved vacuum ultraviolet spectroscopy of self-trapped excitons in KH2PO4 crystals

A complex investigation of the dynamics of electronic excitations in potassium dihydrophosphate (KDP) crystals is performed by low-temperature time-resolved vacuum ultraviolet optical luminescence spectroscopy with subnanosecond time resolution and with selective photoexcitation by synchrotron radiation. For KDP crystals, data on the kinetics of the photoluminescence (PL) decay, time-resolved PL spectra (2-6.2 eV), and time-resolved excitation PL spectra (4-24 eV) at 10 K were obtained for the first time. The intrinsic character of the PL of KDP in the vicinity of 5.2 eV, which is caused by the radiative annihilation of self-trapped excitons (STEs), is ascertained; sigma and pi bands in the luminescence spectra of the STEs, which are due to singlet and triplet radiative transitions, are resolved; and the shift of the sigma band with respect to the pi band in the spectra of the STEs is explained. (C) 2003 MAIK Nauka/Interperiodica.