On the influence of the local vibration on spectral and laser characteristics of F2- colour centres in LiF crystals at low temperatures

A study of spectral and laser properties of the LiF:F₂^- crystal at low temperatures has revealed an electronic – vibrational interaction of electrons of the F₂^- centre with the local vibration of the centre, which occurs against the background of coupling between electrons of F₂^- centres and lattice phonons. The interaction of electrons with the local vibration manifests itself in spectra in the form of narrow lines superimposed on wide electron-phonon lines that are due to the electron-lattice interaction. An anomalous behaviour of spectral LiF:F₂^- laser lines is also found at liquid nitrogen temperature upon selective excitation; this behaviour is explained by the difference in the probabilities of the lattice and local interactions.