Time-resolved measurements of atomic photoionization are at the forefront of atomic and molecular physics. Recent experiments with ultra-short laser pulses show that the photoemission occurs on a finite time scale which is of the order of tens of attoseconds (1 as = 10-18 s). To resolve such a short time, the ionizing XUV laser pulse initiates the photoemission process, and a probing IR pulse steers the photoelectron towards the detector. The time delay between the pump and probe pulses is converted to the photoelectron energy (attosecond streaking) or yield (RABBITT technique).
The talk will provide an overview of the theoretical investigations of different ionization phenomena resulting from exposure of closed-shell atoms and atomic species to short and intense laser pulses. The main theoretical tool employed is the time-dependent Schrodinger equation (TDSE) for treating laser atom interaction in single active electron (SAE) approximation and random phase approximation with exchange (RPAE) for treating laser-matter interaction perturbatively while keeping the full account of inter-electron interaction. These methods are implemented within efficient computer codes deployed in a multi-processor supercomputer environment. These numerical results reveal important aspects of ultrafast electron dynamics in atomic ionization.