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

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

Conferencia; 12th Eurepean Conference on Atoms, Molecules, and Photons; 2016

Goethe Universität

Recent experiment 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] and references therein).A recent 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) configuration of Ti:sapphire laser (800 nm). To shed more light in ionization process we perform simulations with the time dependent Schödinger equation andcompare this results with the strong field and Coulomb-Volkov approximations. We find that time delays depend on the definition from electron momentum distributions. Besides, we also find a large discrepancy between the resultspredicted by the strong field approximation (zero delay for sidebands) and numerical solutions of time-dependent Schrödinger equation at the highest simulation energies. We also find that the strong assumption of additive timedelays adopted in streaking or RABBITT techniques [3], needs to be revisited when applied to the case of (w,2w) lasers due to the multiplicity of coherent quantum paths leading to a final multiphoton peak.As an example, we show in Fig. 1 time delays obtained from asymmetries and forward emission (considering integrations over ±z hemispheres).[1] R. Pazourek, S. Nagele, and J. Burgdörfer, Attosecond chronoscopy of photoemission, Rev. of Mod. Phys., 87, 765, (2015).[2] L. J. Zipp, A. Natan, and P. H. Bucksbaum, Probing electron delays in above-threshold ionization, Optica 1, 361-364 (2014).[3] J. Feist, O. Zatsarinny, S. Nagele, R. Pazourek, J. Burgdörfer, X. Guan, K. Bartschat and B. I. Schneider, Time delays for attosecond streaking in photoionization of neon, Phys. Rev. A, 89, 033417, (2014).