We present a joint experimental and theoretical study of ionization of argon atoms by a linearly polarized two-color laser field (λ 1 = 800 nm, λ 2 = 400 nm). Changing the relative phase ϕ between the two colors, the forward-backward asymmetry of the doubly differential momentum distribution of emitted electrons can be controlled. We find excellent agreement between the measurements and the solution of the time-dependent Schrödinger equation in the single-active electron approximation. Surprisingly we also find good agreement between the quantum and classical calculations of electron momentum distributions generated by lasers at optical wavelengths.

A theoretical study of ionization of the hydrogen atom due to an XUV pulse in the presence of an IR laser is presented. Well-established theories are usually used to describe the laser assisted photoelectron effect. However, the well-known softphoton approximation firstly posed by Maquet et al in Journal of Modern Optics 54 1847 (2007) and Kazansky's theory in Phys. Rev. A 82, 033420 (2010) completely fails to predict the electron emission prependicularly to the polarization direction. Making use of a semiclassical model, we study the angle-resolved energy distribution of photoelectrons for the case that both fields are linearly polarized in the same direction. We thoroughly analize and characterize two different emission regions in the angle-energy domain: (i) the parallel-like region with contribution of two classical trajectories per optical cycle and (ii) the perpendicular-like region with contribution of four classical trajectories per optical cycle. We show that our semiclassical model is able to asses the interference patterns of the angle-resolved photoelectron spectrum in the two different mentioned regions. Electron trajectories stemming from different optical laser cycles give rise to angle-independent intercycle interference known as sidebands. These sidebands are modulated by an angle-dependent coarse-grained structure coming from the intracycle interference of the electron trajectories born during the same optical cycle. We show the accuracy of our semiclassical model as a function of the time delay between the IR and the XUV pulses and also as a function of the laser intensity by comparing the semiclassical predictions of the angle-resolved photoelectron spectrum with the continuum-distorted wave strong field approximation and the ab initio solution of the time dependent Schrödinger equation

This work presents a theoretical study of fully differential cross sections (FDCSs) for the double ionization of an He target by ion impact within a distorted wave model. The initial atomic system is described by two approximated wave functions of different accuracy proposed by Bonham and Kohl. For the final channel several models are considered based upon improvements and simplifications of the well-known three-body Coulomb (3C) model. The influence of the receding projectile on the resulting fragments is also studied by implementing a model with effective charges that depend on the momenta of the four particles. The FDCSs resulting for different electron energy sharing are discussed. The sensitivity of the FDCSs to the projectile charge sign and magnitude is explored over the energy range 700 keV/amu through 6 MeV/amu.

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