Relaxation jumps and hot luminescence of self-trapped excitons

A nonperturbative theory of anharmonic multiphonon decay of strong local vibrations in crystals is presented, The theory predicts a slow-down of the decay at large amplitudes, and a jump-like acceleration of the decay near the critical amplitudes of similar to 0.3 Angstrom. A local vibration with such or larger amplitude is created, e.g. on exciting self-trapped excitons in solid Xe. The time evolution of this vibration manifests itself in the hot luminescence of this crystal. A comparison of the calculated and the observed spectra allows one to conclude that the relaxation rate of the self-trapped exciton in solid Xe has indeed a strong maximum at the amplitude of similar to 0.3 Angstrom. (C) 1998 Elsevier Science B.V. All rights reserved.