Semiclassical description of multiphoton processes - art. no. 053403

We analyze strong held atomic dynamics semiclassically, based on a fun time -dependent description with the Hermann-Kluk propagator. From the propertie s of the exact classical trajectories, in particular the accumulation of ac tion in time, the prominent features of above-threshold ionization and high er-harmonic generation are proven to be interference phenomena. They are re produced quantitatively in the semiclassical approximation. Moreover, the b ehavior of the action of the classical trajectories supports the so called strong field approximation which has been devised and postulated for strong field dynamics.