Photoionization of atoms confined in C$_{60}$ versus C$_{240}$: Giant enhancement and attosecond delay

We investigate the effects of confinement and electron correlation on the photoemissions of noble gas atoms sequestered endohedrally in C$_{60}$ versus C$_{240}$. The time-dependent local density approximation (TDLDA) method [1] with Leeuwen and Baerends (LB94) exchange-correlation functional is employed. We study the moduli and phases of the photoionization dipole matrix elements involving atomic-type as well as atom-fullerene hybrid-type levels of the molecules and extract associated cross sections and angle-integrated Wigner-Smith time-delays [2]. We examine the size effects of the molecular cage on the plasmonically enhanced strength of the atomic ionization [3]. Furthermore, the behavior of emission time delays in attoseconds, induced by this enhancement as well as by the confinement-modified atomic Cooper minima, as a function of fullerene size is scrutinized in detailed. \\[4pt] [1] Madjet et al., PRA 81, 013202 (2010);\\[0pt] [2] Dixit at al., PRL 111, 203003 (2013);\\[0pt] [3] Madjet et al., PRL 99, 243003 (2007).