Relaxation Jumps and Hot Luminescence of Excitons in Rare Gas Crystals

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 its jump–like acceleration near the critical amplitudes of ≍ 0.3 Å. Local vibration with such or larger amplitude is created e.g. on exciting quasi–molecules (localised excitons)\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document} $$ Xe_2^* $$ \end{document}in solid Xe. The time evolution of this vibration manifests itself in the hot luminescence of Xe crystal. A comparison between the calculated and the observed spectra allows one to conclude that the relaxation rate of\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document} $$ Xe_2^* $$ \end{document}in solid Xe has indeed a strong maximum at the amplitude of ≍ 0.3 Å.