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Bejan Ghomashi

Publications and source records attributed to Bejan Ghomashi.

2 recordsLinked to original sources
arXiv2021

Attosecond Intramolecular-Scattering and Vibronic Delay

The photoionization of the CO molecule from the C$-1s$ orbital does not obey the Franck-Condon approximation, as a consequence of the nuclear recoil that accompanies the direct emission and intra-molecular scattering of the photoelectron. We use an analytical model to investigate the temporal signature of the entangled nuclear and electronic motion in this process. We show that the photoelectron emission delay can be decomposed into its localization and resonant-confinement components. Finally, photoionization by a broadband soft-x-ray pulse results in a coherent vibrational ionic state with a tunable delay with respect to the classical sudden-photoemission limit.

physics.atom-ph↗
arXiv2019

Resonant Anisotropic Emission in Two-Photon Interferometric Spectroscopy

We theoretically explore a variant of RABBITT spectroscopy in which the attosecond-pulse train comprises isolated pairs of consecutive harmonics of the fundamental infrared probe frequency. In this scheme, one-photon and two-photon amplitudes interfere resulting in an asymmetric photoelectron emission. This interferometric principle has the potential of giving access to the time-resolved ionization of systems that exhibit autoionizing states, since it imprints the group delay of both one-photon and two-photon resonant transitions in the energy-resolved photoelectron anisotropy as a function of the pump-probe time delay. To bring to the fore the connection between the pump-probe ionization process and its perturbative analysis, on the the one side, and the underlying field-free scattering observables as well as the radiative couplings in the target system, on the other side, we test this scheme with an exactly solvable analytical one-dimensional model that supports both bound states and shape-resonances. The asymmetric photoelectron emission near a resonance is computed using perturbation theory as well as solving the time-dependent Schödinger equation; the results are in excellent agreement with the field-free resonant scattering properties of the model.

physics.atom-ph↗