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 from the illuminating star can be explained by luminescence emission of UV irradiated and Cu or rare-earth-doped glassy particles.