Two-photon-excited luminescence of mixtures of organic polycrystalline substances

An investigation was made of the spectra of the two-photon-excited luminescence of mixtures of polycrystalline aromatic substances with polycrystalline sodium chloride. A redistribution of the intensity in these spectra was observed when the concentration of the aromatic compound was altered. The conditions for transition from spontaneous luminescence to superradiance in such heterogeneous systems were analysed.