Photoelectron correlation effects

These may be generated by irradiating an atom with a beam of monochromatic X-rays or ultraviolet rays. X-ray and electron spectroscopy is one of the main methods used for studying the structure of atomic electronic shells, particularly inner ones, as well as the role of relativistic and correlation effects. A wealth of such information may also be obtained from the studies of angular distribution of photoelectrons. It is interesting to notice that with increase of the energy of X-rays the dipole approximation fails to correctly describe the angular distribution of electrons. 

Correlations between electrons in initial and final states lead not only to the shift of photoelectron lines, changes of their forms and redistribution of their intensities, but also to the occurrence of so-called satellite lines, corresponding to photoionization with the excitation of the other electron. Correlation effects in photoelectron spectra are caused by mixing of configurations separately in the initial state, in the final ion and in the final state of continuum. 

Correlation effects in Auger spectra may be classified similarly to those in the case of photoelectron spectra. Strong correlation effects occur in... 

Fig. 6a-e. Fermi sea correlation effects in photoionization (a) One-electron level scheme, (b)—(d) Feynman diagrams describing monopole (K = 0), dipole (K = 1) and quadrupole (K = 2) fluctuation (correlation) processes and (e) schematic pictures of the resulting photoelectron spectrum... 

Ultraviolet photoelectron spectroscopy combined with ab initio calculations of the five- and six-membered unsaturated rings containing phosphorus and arsenic have been studied <1995JST57>. Assigning the spectra, no defect of Koopmans theorem has been found in the low-ionization-energy region. Reorganization and correlation effects should be comparable and be considered free from any defects of Koopmans theorem. 

In a mainly experimental work, Fujihara et al performed photoelectron spectroscopy experiments on Na2 in small water clusters, i.e., Na2 (H20)K with w < 6. In addition, they performed electronic-structure calculations with Hartree-Fock plus 2nd order Moller-Plesset perturbation treatment of correlation effects. Further... 

D.R. Beck, C.A. Nicolaides, Specific correlation effects in inner-electron photoelectron... 

The development of accurate calculations for the excited states involved in XANES spectroscopy closely mirrors developments in ground-state calculations in molecules and solids. There are, however, several important differences, such as the necessity of a core-hole potential, the core-hole lifetime and final-state photoelectron lifetime effects, possible multi-channel effects, and the energy dependence of the exchange-correlation potential, which complicate the physical model but which may in principle be dealt with, although work continues in all of these areas. 

CORRELATION EFFECTS STUDIED BY MEANS OF PES Shift and distortion of main photoelectron line... 

---