Two-photon excitation spectra of exciton luminescence in CaF2 obtained by using synchrotron radiation and laser

Abstract Excitonic states in CaF2 are studied with luminescence-detected two-photon spectroscopy using synchrotron radiation and laser. The two-photon excitation spectrum for the luminescence due to self-trapped excitons (STEs) exhibits a clear peak on the high-energy side of the 1S exciton band. The peak is assigned to the 2P exciton state. The two-photon excitation spectrum for perturbed-STE luminescence is different from that for the STE luminescence, suggesting that localized excitons generated by SR are re-excited by the laser irradiation.