RELAXATION JUMPS AND HOT LUMINESCENCE OF SELF-TRAPPED EXCITONS

A nonperturbative theory of anharmonic multiphonon decay of strong loc al vibrations in crystals is presented, The theory predicts a slow-dow n of the decay at large amplitudes, and a jump-like acceleration of th e decay near the critical amplitudes of similar to 0.3 Angstrom. A loc al vibration with such or larger amplitude is created, e.g. on excitin g self-trapped excitons in solid Xe. The time evolution of this vibrat ion manifests itself in the hot luminescence of this crystal. A compar ison 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.