Evidence for a surface exciton in KBr via laser desorption - art. no. 125423

We demonstrate that direct photoexcitation of the single crystal KBr surfac e leads to desorption of hyperthermal neutral bromine atoms. We have produc ed separately the hyperthermal and the near-thermal components of neutral h alogen emission from an alkali halide. The source of hyperthermal bromine e mission is attributed to decay of a surface exciton excited at photon energ ies below that of the bulk exciton. We argue that the frequently observed n ear-thermal component is derived from excitation within the bulk crystal. O ur experimental data provide strong support to a theoretical excitonic emis sion model previously described in the literature.