Results of a theoretical study of photoionization cross sections and photoelectron angular asymmetry parameters of atoms confined by positively ${\mathrm{C}}_{60}^{+z}$ or negatively ${\mathrm{C}}_{60}^{-z}$ charged fullerene shells are presented. For negatively charged ${\mathrm{C}}_{60}$, entirely new confinement resonances, termed Coulomb confinement resonances, that dominate the spectra of the encapsulated atoms are predicted. In addition, the effect of a negative ${\mathrm{C}}_{60}$ shell is to move some of the oscillator strength of the encapsulated atom from the discrete excitation region into the continuum. For positively charged ${\mathrm{C}}_{60}$, the situation is much different; no Coulomb confinement resonances occur in the photoionization spectrum of the encapsulated atom, and charging the shell positively does nothing to the photoionization cross section (as a function of photon energy) except to increase the threshold energy. The findings result from model Hartree-Fock calculations of $1s$ photoionization of Ne confined by neutral, negative, and positive ${\mathrm{C}}_{60}$.

Angular dependence of photoemission time delay for the valence $n{p}_{3/2}$ and $n{p}_{1/2}$ subshells of Ar, Kr, and Xe is studied in the dipole relativistic random phase approximation. Strong angular anisotropy of the time delay is reproduced near respective Cooper minima while the spin-orbit splitting affects the time delay near threshold.

A fully quantum-mechanical modification to the R-matrix method is introduced to include the recapture of slow photoelectrons following Auger decay of an inner-shell vacancy state and is applied to the photodetachment of ${\mathrm{Li}}^{-}$ above the ${1s}^{-1}$ threshold. The results show excellent agreement with experiment and resolve a large discrepancy in the cross section near the $1s$ threshold between theory and experiment.

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 ${\mathrm{C}}_{n⩾240}$. 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 ${\mathrm{C}}_{60}$, ${\mathrm{C}}_{240}$, ${\mathrm{C}}_{540}$, ${\mathrm{C}}_{60}@{\mathrm{C}}_{240}$, and ${\mathrm{C}}_{60}@{\mathrm{C}}_{240}@{\mathrm{C}}_{540}$ 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.

The angular distribution for Ar 2p photoionization has been measured from just above threshold to 400 eV photon energy, and calculated in the same energy range using the relativistic random-phase approximation. The present experimental and theoretical results are in good agreement, but disagree somewhat with earlier Hartree-Fock (HF) calculations. The HF values are found to be significantly higher in the near-threshold region. Possible reasons for this discrepancy are discussed with relevance to the general understanding of inner-shell photoionization phenomena.

The angular dependence of photoemission time delay for the inner $n{d}_{3/2}$ and $n{d}_{5/2}$ subshells of free and confined Xe is studied in the dipole relativistic random phase approximation. A finite spherical annular well potential is used to model the confinement due to fullerene $C_{60}$ cage. Near cancellations in a variety of the dipole amplitudes, Cooper-like minima, are found. The effects of confinement on the angular dependence, primarily confinement resonances, are demonstrated and detailed.