Photoionization of atoms confined in giant single-walled and multiwalled fullerenes

Results of a theoretical study of photoionization cross sections and photoelectron angular distribution asymmetry parameters of an atom A confined in spherical multiwalled fullerenes are presented and compared with those obtained for the free atom A as well as for A confined in giant spherical single-walled fullerenes C_n⩾240. Each individual nested fullerene cage is represented by a spherical, short-range, attractive potential characterized by the inner radius, width, and potential depth. Trends in the strength and location of confinement resonances in the photoionization spectra, as a function of the number of nested fullerenes, are delineated. As examples, calculations of the 1s photoionization of Ar confined in C₆₀, C₂₄₀, C₅₄₀, C₆₀@C₂₄₀, and C₆₀@C₂₄₀@C₅₄₀ are presented. The calculations are performed within the framework of a Hartree-Fock approximation which is appropriate for a deep inner-shell photoionization. The trends seen should be a general occurrence for an inner-shell photoionization of virtually any atom confined in spherical fullerenes not only Ar.