Peculiarities of the Electron–Phonon Interaction in the Spectra of the Molecular Ions O, S, and NO in Alkali Halide Crystals

A systematic low‐temperature study is made of deformations of no‐phonon lineshapes in the luminescence spectra of small molecular ions in alkali halide crystals. It is shown that the main peculiarities of the temperature broadening and shift of lines arc connected with the selective manner of coupling of the electron transition in the centre with low‐frequency pseudolocal vibrations. This conclusion is confirmed also by the study of the change of the total Stokes' losses on crystalline vibrations with temperature. It is found that the homogeneous no‐phonon lineshapes are Lorentzians with a slight low‐frequency asymmetry.