EXCITON SELF-TRAPPING AND LATTICE DEFECT CREATION IN RARE-GAS SOLIDS AND OTHER INSULATORS

We have studied the possible creation of stable lattice defects induce d by exciton self-trapping (STE) in solid neon. Generally speaking, th e STE-bubbles accompanied with a plastic deformation are found to be a t lower energies than a pure STE-bubble. Those with two vacancies an t he first atomic shelf have the lowest energy. Some of the vacancy-inte rstitial atom pairs escaped mutual annihilation as the electronic sub- system returned to the ground state, thereby stable lattice defects re sulted. The emission energy changes of lattice defect-associated STE h ave been evaluated and are found to be in reasonable agreement with ob served data. Much has been learned recently on the role of the STE in radiation damage creation of ionic halides. We have made a brief compa rison of the ionization induced defect formation processes in the two types of materials. In both cases, the excited electron is the prime d river of the process. lit solid neon the excited electron is directly attracted to the localized hole on Ne, but repelled by the ground stat e Ne atoms. In the halides the excited electron is attracted to the Ma delung potential at an anion site instead. In rare gas solids, the Fre nkel pair is a purely structural defect in the lattice with the electr onic subsystem in its ground state. In ionic halides, the pair of F ce nter and H center is not only an interstitial atom-vacancy pair in the halogen sublattice, but also represents an electronically excited sta te. Because of this difference the way the created Frenkel defects are stabilized in the two types of material is distinct.