Exciton Self-Trapping in Rare-Gas Crystals
Abstract
The problem of exciton self-trapping in rare-gas solids is investigated from a dynamical point of view. Experimental ultraviolet emission spectra from rare-gas solids and liquids have been interpreted as arising from the radiative decay of an excited-state dimer which becomes localized in the substance. This embedded dimer can arise from electron capture by a self-trapped hole (R2+), or by the dynamical trapping of an exciton into an excimer state (R2*). A study of the vibrational relaxation of a molecule embedded in a solid leads to a fast trapping process in which an exciton becomes localized for all the heavy rare-gas substances. This localization is achieved within 6 × 10−12 sec by means of a resonant transfer relaxation process in which two neighboring atoms lose sufficient energy (∼ 0.5 eV) to become stabilized in a lower vibrational state of the excimer.