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A model for the calculation of photoionization cross sections of an atom inside the fullerene cage is proposed. In the frame of this model the M@C60 endohedral is considered as an isolated M atom located in the centre of the spherically symmetrical fullerene shell. The potential of this shell is written as the Dirac delta function in the radial coordinate. On the basis of this model a comparative study of the photoionization cross sections of an isolated M atom and the same atom in M@C60 is carried out. It is shown that near the thresholds of ionization of atomic subshells the resonance peaks appear in the photoeffect cross sections. The positions of these resonances on the scale of photoelectron energy are defined by the fullerene radius and the affinity energy of an electron to C60. The general formulae derived are used to calculate the photoionization cross sections of the inner subshells of the He, Ne and Ca atoms inside the fullerene cage.

A. Multielectron Correlation Effects in Collisions A.1. Probing Correlations through Spin-Orbit InteractionRecently, a new aspect of interchannel coupling has been found [1], known as spin-orbit activated interchannel coupling, stimulated by an experimental study on photoionization of Xe in the vicinity of the 3d threshold. This effect results only through the spin-orbit splitting of innershell thresholds. Effects of spin-orbit activated interchannel coupling on nondipole [2] photoelectron angular distribution asymmetry parameters have been discussed, including the spin-polarization of photoelectrons from 3d electrons of Xe, Cs and Ba, concluding that through spin-orbit interaction polarization can be achieved and correlation probed.Public reporting burden for this collection of information is estimated to average 1 hour per response, including ii is, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send'

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Approximating the C60 shell as a collection of carbon atoms, the potential experienced by a confined atom has been calculated within the framework of the self-consistent spherical jellium model. It has been found that the potential well in this model has a cusp-shaped Lorentz-like profile. The parameters of the model Lorentz-bubble potential (depth and thickness) have been selected so that in the potential well there would be an electronic level corresponding to the experimental electron affinity of the C60 molecule. The spatial distribution of the positive charge of the C-atomic nuclei and the negative charge of the electron clouds forming the electrostatic potential of C60, as a whole, has been analyzed using the Poisson equation. It is demonstrated that the often used radial square-well potential to approximate the C60 corresponds to a non-physical charge density for the C60 molecule. This analysis demonstrates that the phenomenological potentials simulating the C60 shell potential should belong to a family of potentials with a non-flat bottom and non-parallel potential walls similar to the Lorentz-bubble potential. The photoionization cross-sections of a hydrogen atom localized at the center of the C60 shell have been calculated as well. It is found that confinement oscillations in the cross-sections are exhibited within the framework of the cusp-shaped potential model and these oscillations are essentially the same as those in the case of the potential wells with well-defined borders (parallel walls), thereby demonstrating that the inherent characteristic distances of the potential, e.g., radii of the potential walls, or the distances between potential walls, are not necessary to produce confinement resonances; this should be a general result for atoms or molecules confined in near-spherical fullerenes.