Spatial distribution of the wave function of the self-trapped exciton in AgCl

The results are presented of a high-frequency electron nuclear double resonance (ENDOR) study of the lowest triplet state of the self-trapped exciton in AgCl. Direct information about the spatial distribution of the wave function is obtained, which confirms that the exciton in its triplet state is built up from a strongly localized self-trapped hole and a very diffuse electron. The electron is mainly contained in a hydrogenlike 1s orbital with a Bohr radius of 15.1±{}0.6 {}, but near its center the electron density deviates from spherical symmetry and reflects the D₄ₕ charge distribution of the hole. From a comparison with the results of an ENDOR study of the self-trapped hole, it is concluded that the microscopic and electronic structure of a self-trapped hole is not significantly altered by the attraction of a shallow electron. No evidence is obtained for the formation of Frenkel pairs in AgCl upon ultraviolet irradiation at low temperatures. {} 1996 The American Physical Society.