We simulate angular resolved RABBITT (Reconstruction of Attosecond Beating By Interference of Two-photon Transitions) measurements on valence shells of noble gas atoms (Ne, Ar, Kr, and Xe). Our non-perturbative numerical simulation is based on solution of the time-dependent Schrödinger equation for a target atom driven by an ionizing XUV and dressing IR fields. From these simulations we extract the angular dependent magnitude and phase of the RABBITT oscillations and deduce the corresponding angular anisotropy β parameter and Wigner time delay τW for the single XUV photon absorption which initiates the RABBITT process. Said β and τW parameters are compared with calculations in the random phase approximation with exchange (RPAE) which includes inter-shell correlation. This comparison is used to test various effective potentials employed in the one-electron TDSE. In lighter atoms (Ne and Ar), several effective potentials are found to provide accurate simulation of RABBITT measurements for a wide range of photon energies up to 100 eV above the valence shell threshold. In heavier atoms (Kr and Xe), the onset of strong correlation with the d-shell restricts the validity of the single active electron approximation to several tens of eV above the valence shell threshold.
We predict an observable Wigner time delay in outer atomic shell photoionization near inner shell thresholds. The near-threshold increase of time delay is caused by inter-shell correlation and serves as a sensitive probe of this effect. The time delay increase is present even when the inner and outer shell thresholds are hundreds of electron volts apart. We illustrate this observation by several prototypical examples in noble gas atoms from Ne to Kr. In our study, We employ the random phase approximation with exchange (RPAE) and its relativistic generalization RRPA. We also support our findings by a simplified, yet quite insightful, treatment within the lowest order perturbation theory.
We consider photoemission from the 4d shell of the free Xe and encapsulated Xe@C 60 atoms by ionizing XUV and probing IR fields typical for a RABBITT (reconstruction of attosecond beating by interference of twophoton transitions) measurement. Our theoretical model is based on the numerical solution of the time-dependent Schrödinger equation in the single-active-electron approximation. The fullerene C 60 cage is represented by a finite-width well potential. We test our model against an analogous set of nonrelativistic [Phys. Rev. A 89, 053424 (2014)] and relativistic [Phys. Rev. A 96, 053407 ( 2017)] calculations for the 4d shell of Xe and Xe@C 60 driven by a continuous XUV field. Based on this verification, we make predictions for the total ionization probability, angular anisotropy β parameter, and the angular-dependent atomic time delay τ a from the threshold to several hundred eV of excess energy.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.