Exciton luminescence spectra of CuCl films and their change by photo-irradiation

We have observed luminescence spectra of vapor-deposited CuCl films on rutile TiO2 under photo-irradiation with picosecond light pulses at 4.6 K. Decrease in the Z3-exciton and I1 luminescence intensities and an appearance of new exciton luminescence are found to be induced by the photo-irradiation. From the excitation photon energy dependence of the luminescence spectra, it is found that the Z3-exciton luminescence is resolved into two components: one is attributed to the optical phonon Raman lines and the other to the free Z3-exciton luminescence. The intensity of the Raman lines resonantly increases at the Z3-exciton band resulting in the optical phonon structures in the excitation spectrum. The excitation spectra of the new exciton and I1 luminescence are similar to the absorption spectrum of CuCl, which suggest that the resonant Raman process observed in the Z3-exciton luminescence hardly contributes to the generation of the excitons associated with the new exciton and I1 luminescence.