A time-resolved luminescence spectroscopy study of self-trapped excitons in NH4H2PO4 crystals

A complex investigation of the dynamics of electronic excitations and luminescence in nonlinear optical crystals of ammonium dihydrophosphate NH4H2PO4 was performed using low-temperature vacuum ultraviolet luminescence spectroscopy with time resolution upon selective photoexcitation by synchrotron radiation. Data on the photoluminescence (PL) decay kinetics, time-resolved PL spectra (2-6.2 eV), and time-resolved PL excitation spectra (4-24 eV) were obtained for the first time for NH4H2PO4 crystals at 8 K. It is ascertained that the PL of NH4H2PO4 crystals in the vicinity of 4.7 eV has intrinsic character due to the radiative annihilation of self-trapped excitons. Possible channels of generation and decay of relaxed and unrelaxed electronic excitations in NH4H2PO4 crystals are discussed.