In this book we discuss the photoabsorption processesof several closed shell systems, including atoms thatare trapped inside a fullerene molecule. Energylevels and wavefunctions are studied using Dirac-Fockmethod and we employed Relativistic Random PhaseApproximation (RRPA) and Relativistic MultichannelQuantum Defect Theory (RMQDT) to calculate thephotoionization parameters. Autoionizationresonances in Kr, Xe and Cd atoms and the Si2+ ionhave been presented and these results are discussedin the context of some very recent and sophisticatedexperimental results. The effect of confinement has...