On the possibility of luminescence emission of interstellar grains

The possible occurrence of luminescence emission by different irradiated materials in interstellar space is discussed. It is shown by means of a model computation that the quantum efficiency of luminescence emission is high enough and can, in general, be detected in interstellar space. Further, it is argued that the wavelength-dependent intensity increase observed in the NGC 7023 reflection nebula at the distance of 3.4 arcmin from the illuminating star can be explained by luminescence emission of UV-irradiated and Cu-or rare-earth-doped glassy particles.