HOLE-ELECTRON MECHANISM OF F-H PAIR GENERATION IN RBCL CRYSTALS WITH IMPURITY ELECTRON TRAPS

Production of F, Cl-3(-), Ag-0, and Tl-0 centers in RbCl:Ag and RbCl:T l crystals by photons having energies ranging from 5 to 10 eV has been studied at 295 and 180 K. It is shown that creation of near-impurity excitations is accompanied by formation of F centers localized in the vicinity of Ag+ and Tl+ ions. F centers are produced in direct optical generation of self-trapped excitons. In addition to the well-known me chanism of F-H pair production in nonradiative recombination of electr ons with self-trapped holes, a hole-electron process has been revealed for the first time to operate in RbCl:Ag having deep electron traps. By this mechanism, F-H pairs appear in the following sequence of stage s: thermally stimulated unfreezing of hopping diffusion of self-trappe d holes (VK centers), tunneling electron transfer from Ag-0 to the app roaching V-K centers, and subsequent nonradiative decay of triplet sel f-trapped excitons near Ag+ ions. (C) 1998 American Institute of Physi cs.