Luminescence Excitation by VUV Photons in Alkali and Silver Halides

Excitation spectra of luminescence quantum yield in alkali and silver halides are measured at low temperatures using synchrotron radiation for the energy range up to 30 eV. The yields at the valence exciton excitation are low (0.1 at most) in alkali halides (KCl, KBr and NaBr), but high (0.4) in AgCl. Enhancement of the yield indicative of multiple exciton production is observed at higher energies, and the yields in NaBr and AgCl exceed unity in the energy range studied. Discussion is given for the competition between radiative and non-radiative decay channels during relaxation of excited states.