Solid-state binding, recombination, and Auger energy shifts of rare-earth metals

The free-atom binding energies up to 4d core levels have been determined from monochromatic synchrotron-radiation-excited photoelectron spectra for the elements La, Ce, Nd, Sm, Eu, and Gd. They are compared with the corresponding solid-state values, and the atom-to-metal binding energy shifts are discussed in comparison with the theoretical calculations available. Atomic and solid-state 4d-based Auger and direct recombination (autoionization) spectra of the elements La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, and Tm have also been studied and are compared in detail. The spectra show clearly very different solid-state shifts for the 4d-based Auger and 4d{→}(4f,{ε}f) autoionization peaks indicating a very useful method for distinguishing these two processes in electron-excited spectra. The intensities of the recombination peaks in the spectra of La, Ce, Sm, Eu, and Gd were also measured, using the white-light synchrotron radiation obtained in zeroth order from a toroidal-grating monochromator, and were found to be increased in intensity. The autoionization and Auger energy shifts are discussed in terms of theoretical models.