Photoelectron spectroscopic study of the decay process of excited 4dstates in cesium halides

The nonradiative decay of excited 4d states in CsCl and CsBr was investigated by photoelectron spectroscopy with use of synchrotron radiation. It was observed that the intensities of the Auger-electron peak and Cs 5p photoelectron peak are resonantly enhanced around the Cs 4d excitation energy, while the valence-band intensity is not clearly enhanced. The enhancements are interpreted in terms of two decay processes, the direct recombination and the Auger decay processes, of excited 4d states. It is shown that excited 4d states in CsCl and CsBr decay dominantly through the ${\mathit{N}}_{4,5}$-${\mathit{O}}_{2,3}$ ${\mathit{O}}_{2,3}$ Auger process, and the probability of the direct-recombination decay with the energy transferred to Cs 5p electrons is estimated to be 2–8 %, by using constant-initial-state and absorption spectra.