This collection of papers describes investigations of luminescence centers in II-VI crystal phosphors, ruby, and molecular crystals. These investigations were carried out using spec troscopy in a wide range of wavelengths, electron paramagnetic resonance, and polarization methods. The relationship between the thermal and optical depths of electron traps is con sidered specifically. The articles in this collection should be of interest to all scientists investigating the luminescence of solids. v CONTENTS Investigation of the Spectral-Luminescence Properties of Ruby as Active Laser Medium V....