Theoretical study of time delays in (w,2w) above threshold ionization

S. NAGELE; S. D. LÓPEZ; ARBÓ, D.G.; S. DONSA; BURGDÖRFER, J.

Budapest

Conferencia; The International Conference on Many Particle Spectroscopy of Atoms, Molecules, Clusters and Surfaces; 2018

EKHO' 94 Ltd., Debrecen

Experiments employing either attosecond streaking or the complementary interferometric RABBIT technique have allowed to study photoemission from rare gas atoms and surfaces in the time-domain with attosecond precision. The experimental progress has triggered considerable theoretical efforts to understand photoionization from a time-dependent perspective (see [1] andreferences therein).The experiment in atomic ionization by two-color (w,2w) lasers by Zipp et al. [2] has revealed that a pump-probe scheme can be used to characterize time delays in the emission of electrons in the above-threshold ionization regime for visible frequency of the pump. In this work, we perform a theoretical analysis of the time delays in Ar ionization by two-color laser for a typically (w,2w) conguration of Ti:sapphire laser (800nm). To shed more light in ionization process we perform simulations with the time dependent Schrödinger equation and compare this results with the strong eld and Coulomb-Volkov approximations.We find that time delays depend on the denition from electron momentum distributions. Besides, we also nd a large discrepancy between the results predicted by the strong field approximation (zero delay for sidebands) and numerical solutions of time-dependent Schröodinger equation at the highest simulation energies. We also nd that the strong assumption of additivetime delays adopted in streaking or RABBITT techniques [3] needs to be revisited when applied to the case of (w, 2w) lasers due to the multiplicityof coherent quantum paths leading to a final multiphoton peak. Finally, we explore simpler quantum paths to get a better understanding of the process. For this purpose we use Yukawa potentials tting the electron binding energy toallow the absorption of a desired number of photons to reach the continuum. This analysis paves the way to understand the process and the time delays asociated to each path.