Nonradiative Decay Processes Of 4d Hole States In Csf, Baf2, And Laf3

The nonradiative decay of 4d hole states in CsF, BaF2, and LaF3 was investigated by photoelectron spectroscopy with synchrotron radiation. The N4,5O2,3O2,3 Auger peak is resonantly enhanced around an energy region of 4d excitation of cations. Constant-final-state spectra with the final state at this Auger peak agree well in shape and in energy with respective absorption features. Intensities of 5s and 5p electrons of cations are also resonantly enhanced around the absorption features, while the valence band does not show any enhancement except for LaF3. The spectral shape of constant-initial-state (CIS) spectra with initial states at 5s and 5p levels is different from the absorption features. In particular, intensities of both CIS spectra decrease rapidly relative to their corresponding total photoelectric yield spectra in the higher-energy region. From these results, we propose that 4d hole states decay predominantly through the N4,5O2,3O2,3 Auger process and the direct-recombination processes are suppressed in the higher-energy region. It was also found that the photoemission branching ratio of 5p1/2 to 5p3/2 levels of BaF2 and LaF3 changes drastically at excitation photon energy of the 3D1 state. It is attributed to a difference in the p-d interaction between the 5p1/2 and 5p3/2 hole states at the photoemission final state.