Electron emission perpendicular to the polarization direction in laser-assisted XUV atomic ionization

Abstract

We present a theoretical study of ionization of the hydrogen atom due to an XUV pulse in the presence of an IR laser with both fields linearly polarized in the same direction. In particular, we study the energy distribution of photoelectrons emitted perpendicularly to the polarization direction. By means of a very simple semiclassical model which considers electron trajectories born at different ionization times, the electron energy spectrum can be interpreted as the interplay of intraand intercycle interferences. The intracycle interference pattern stems from the coherent superposition of four electron trajectories giving rise to (i) interference of electron trajectories born during the same half cycle (intrahalfcycle interference) and (ii) interference between electron trajectories born during the first half cycle with those born during the second half cycle (interhalfcycle interference). The intercycle interference is responsible for the formation of the sidebands. We also show that the destructive interhalfcycle interference for the absorption and emission of an even number of IR laser photons is responsible for the characteristic sidebands in the perpendicular direction separated by twice the IR photon energy. We analyze the dependence of the energy spectrum on the laser intensity and the time delay between the XUV pulse and the IR laser. Finally, we show that our semiclassical simulations are in very good agreement with quantum calculations within the strong field approximation and the numerical solution of the time-dependent Schrödinger equation.

Fano’s Propensity Rule in Angle-Resolved Attosecond Pump-Probe Photoionization

“…Conversely, the photoelectron angular distributions (PAD) vary as a function of the delay between the attosecond pulse train and the probe field [22,23]. Modifications of PADs with pump-probe delay have been theoretically predicted [24,25] and the angular dependence of the photoionization time delays in RABBIT measurements has been reproduced in several numerical calculations [21,[26][27][28][29][30]. Nonetheless, the underlying physical origin of these effects is still not understood.…”

Moiré patterns in doubly differential electron-momentum distributions in atomic ionization by mid-infrared lasers

“…The factor B(k) reduces to the two-slit Young interference expression B(k) = 4 cos 2 π/ω S /2 , whereS is given by Eq. (23). We plot the corresponding SPA doubly differential momentum distribution in Fig.…”

Interference in $ω-2ω$ atomic ionization within the strong-field approximation: Beyond the perturbative regime

“…3b). Such discontinuities are an artifact of the SPA and also appears for laser assisted photoionization emission (two colors with one frequency much higher than the other) [54,55]. Again, the minima of the interhalfcycle rings do not match with the sidebands of the intercycle factor in Figs.…”