Intra- and intercycle interferences in XUV-IR ionization

A. A. GRAMAJO; D. G. ARBÓ; R. DELLA PICCA; S. D. LÓPEZ

Budapest

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

EKHO' 94 Ltd., Debrecen

In laser-assisted XUV photoelectric effect (LAPE) the XUV and optical lasers overlap in space and time. When the XUV pulse is longer than the laser period, a photoelectron is emitted into the optical dressing field where one or more quanta of energy can be absorbed and emitted. As a result, the photoelectron spectrum shows sidebands (SBs) separated at energy values given by [1]En = nωL + ωX - Ip - Up,(1)where ωX(L) is the frequency of the XUV (IR) pulse, Ip is the ionization potential, Up the ponderomotive energy, and n is the number of absorbed/emitted IR photons.In this work, we study the angle-resolved energy distribution of photoelectron for the case that both fields are linearly polarized in the same direction making use of the semiclassical model (SCM) [2,3,4]. We thoroughly analyze and characterize two different emission regions in the angle-energy domain: The parallel-like and the perpendicular-like regions. In the former, two classical electron trajectories per optical cycle contribute to the (intracycle) interference pattern which modulates the sidebands stemming from the (intercycle) interference of the electron trajectories at different optical cycles. In the latter, there are four classical trajectories per optical cycle contributing to the intracycle factor.We have studied the dependence of our SCM as a function of the time delay between the IR and the XUV pulses and also as a function of the laser intensity. We also have checked the accuracy of 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 [4].