Stability of Relaxed States of Excitons in Cesium Halides

Stability of relaxed excitons in CsCl-type cesium halides, which are described by a cluster model already developed in a previous paper, is studied. The particle (electron or hole)–phonon interaction is used, in which the discreteness of crystal is emphasized. By a semi-empirical method based on the Landau-Pekar theory, the relaxation energies are calculated for one-particle states as well as exciton states. The results are consistent with those obtained experimentally. Nous avons etudie la stabilitye des excitons relaxes, decrits par un modele de cluster, deja developpe dans un precedent travail, dans les halogenures de cesium a structure CsCl. Nous utilisons l'interaction particle (electron ou trou)-phonon dans laquelle nous faisons ressortir la nature discrete du cristal. Les energies de relaxation sont calculees pour des etats a une particle ainsi que pour les etats excitoniques a l'aid d'une methode semi-empirique basee sur la theorie de Landau-Pekar. Les resultats sont consistants avec ceux obtenus experimentalement.