The dynamics of the photoionization of the two outermost orbitals of ${\mathrm{C}}_{60}$ has been studied in the oscillatory regime from threshold to the carbon $K$ edge. We show that geometrical properties of the fullerene electronic hull, such as its diameter and thickness, are contained in the partial photoionization cross sections by examining ratios of partial cross sections as a function of the photon wave number in the Fourier conjugated space. Evaluated in this unconventional manner photoemission data reveal directly the desired spatial information.

A theoretical study of the subshell photoionization of the Xe atom endohedrally confined in C60 is presented. Powerful hybridization of the Xe 5s state with the bottom edge of C60$\hskip0.3em${}$\pi${} band is found that induces strong structures in the 5s ionization, causing the cross section to differ significantly from earlier results that omit this hybridization. The hybridization also affects the angular distribution asymmetry parameter of Xe 5p ionization near the Cooper minimum. The 5p cross section, on the other hand, is greatly enhanced by borrowing considerable oscillator strength from the C60 giant plasmon resonance via the atom-fullerene dynamical interchannel coupling. Beyond the C60 plasmon energy range the atomic subshell cross sections display confinement-induced oscillations in which, over the large 4d shape resonance region, the dominant 4d oscillations induce their ``clones'' in all degenerate weaker channels known as correlation confinement resonances.

We investigate numerically the recently proposed technique of pulse self-compression by filamentation in noble gases. We show that propagation of a 30 fs infrared pulse containing a few mJ of energy leads to a few-cycle pulse in xenon, krypton, argon, and neon. We describe the different mechanisms and stages of self-compression in the different gases and show that neon, with the highest ionization potential, allows compression to the shortest durations and highest peak intensities. We discuss the process by which an unavoidable frequency modulation of the self-compressed filament simultaneously allows the generation of isolated attosecond (as) pulses via high-order harmonic generation and limits the conversion efficiency of the as pulses.

Considering an Ar atom endohedrally sequestered in ${\mathrm{C}}_{60}$, a phenomenal increase in the photoionization cross section of the confined atom through the dominant outer $3p$ channel is predicted. The effect occurs owing to a powerful dynamical coherent interchannel coupling between the atomic and the cage ionization channels which redirects the bulk of oscillator strength from the giant surface plasmon to the atomic ionization.

The effects of confinement and electron correlations on the relative time delay between the $3s$ and $3p$ photoemissions of Ar confined endohedrally in ${\mathrm{C}}_{60}$ are investigated using the time-dependent local density approximation\char22{}a method that is also found to mostly agree with recent time delay measurements between the $3s$ and $3p$ subshells in atomic Ar. At energies in the neighborhood of $3p$ Cooper minimum, correlations with ${\mathrm{C}}_{60}$ electrons are found to induce opposite temporal effects in the emission of Ar $3p$ hybridized symmetrically versus that of Ar $3p$ hybridized antisymmetrically with ${\mathrm{C}}_{60}$. A recoil-type interaction model mediated by the confinement is found to best describe the phenomenon.

We show that isolated subfemtosecond, extreme ultraviolet (XUV) pulses can be generated via harmonic generation in argon by few-cycle infrared pulses formed through filamentation-induced self-compression in neon. Our calculations show that the time structure of the XUV pulses depends sensitively on both the amplitude and the phase modulation that are induced in the driving pulse during the self-compression process.