Intra- and intercycle interference of electron emission in laser assisted XUV atomic ionization

Abstract

We study the ionization of atomic hydrogen in the direction of polarization due to a linearly polarized XUV pulse in the presence of a strong IR laser. We describe the photoelectron spectra as an interference problem in the time domain. Electron trajectories stemming from different optical laser cycles give rise to intercycle interference energy peaks known as sidebands. These sidebands are modulated by a coarse-grained structure coming from the intracycle interference of the two electron trajectories born during the same optical cycle. We make use of a simple semiclassical model that offers the possibility to establish a connection between emission times and the photoelectron kinetic energy. We analyze such interference pattern as a function of the time delay between the IR and the XUV pulses and also as a function of the laser intensity. We compare the semiclassical predictions with the continuum-distorted-wave strong-field approximation and the ab initio solution of the time-dependent Schrödinger equation.