Core-hole migration and relaxation effect in alkali halide excited by synchrotron radiation

Abstract

Photoluminescence due to radiative transitions between the valence and outermost core bands, in which the Auger process is energetically forbidden, is studied in mixed ${\mathrm{Rb}}_{1\mathrm{-}\mathit{x}}$ ${\mathrm{Cs}}_{\mathit{x}}$F crystals. The results provide clear evidence that a hole created in the ${\mathrm{Rb}}^{+}$ 4p core band migrates through the crystal, and is trapped at the ${\mathrm{Cs}}^{+}$ 5p core state. The diffusion coefficient of the core holes is estimated to be 1.5×${10}^{\mathrm{-}5}$ ${\mathrm{cm}}^2$/s. Furthermore, a comparison with photoelectron data reveals an important role of relaxation effects in the deexcitation process of core holes.