Electron spectroscopic investigation of atomic 4d giant resonances for Ba, La and lanthanides

The 4d-1(4, ε)f giant resonances of atomic Ba, La and lanthanides have been studied by electron spectroscopy using undispersed and monochromatized synchrotron radiation of the storage rings BESSY and DORIS, as well as 1.5 keV electrons for excitation. The atomic vapours have been produced inside a high temperature furnace heated by electron bombardement. The measured spectra give detailled information about electron correlation effects and the character of the giant resonances. Starting from a 4d-1εf atomic shape resonance at Ba they change into discrete 4d-14f excitations with increasing atomic number. Many-body theories succeed to describe the gross features of the determined partial cross-sections for photoionization of 4d, 4f, 5s, 5p, 5d and 6s shells. The experimental free atom ionization, Auger and resonance energy values have been compared with corresponding solid state results. The extra-atomic influence gives rise to energy shifts and valence changes. (orig.)