We conduct a systematic study of the dipole phase and the photoelectron group delay (Wigner time delay) in inner shell photoionization of noble gas atoms from Ne to Xe. Our study encompasses the tender x-ray spectral range and extends to 1 keV photoelectron energy. We employ both the relativistic and the nonrelativistic versions of the random-phase approximation with exchange. We identify the long-range Coulomb and short-range Hartree-Fock contributions to the dipole phase which governs the Wigner time delay variation from the threshold to the whole considered range of photoelectron energies. © 2015 American Physical Society.

Soumyajit Saha

Approximation algorithms

Inert gases

Photoelectrons

Photoionization

Photons

Time delay

Hartree-Fock

INNER SHELL PHOTOIONIZATION

Noble gas atoms

NONRELATIVISTIC

PHOTOELECTRON ENERGY

RANDOM PHASE APPROXIMATION WITH EXCHANGES

Spectral range

Systematic study

Group delay

Fulltext

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IIT Madras

Physical Review A - Atomic, Molecular, and Optical Physics

Using Cl- as a test case, Wigner time delay in the photodetachment process has been investigated theoretically, along with the photoionization of the isoelectronic Ar atom, for the outer 3p shell using the relativistic-random-phase approximation (RRPA). Time delay was probed in these systems from threshold to 80 eV, to investigate threshold effects, the centrifugal barrier shape resonance, and the Cooper minimum region. This study focuses on Cl- because, for negative ions, the phase of the photoemission process is not dominated by the Coulomb phase as it is in photoionization. The results show significant differences, both qualitative and quantitative, between the time delays for Cl- and Ar photoemission at low photoelectron energy, but they are rather similar in the Cooper minimum region, where the Coulomb phase is small. In particular, the Wigner time delay in Cl- exhibits a dramatic energy dependence just above threshold, and a rapidly increasing time delay in the vicinity of the shape resonance. A strong angular dependence of time delay has also been found near the threshold region for the Cl- case, and is absent in the case of the photoionization of Ar. The origin of these phenomenologies is explained and a prospectus for future work is presented. © 2019 American Physical Society.

Physical Review A

Wigner time delay in photodetachment

We uncover dramatic variations of the Wigner photoemission time delay with energy and angle in the vicinity of a Fano resonance with the time delay taking opposite signs at different angles at the same energy as well as at the opposite sides of the resonance at the same angle. These variations are illustrated by choosing the Ne 2s→3p autoionizing state as a case study. Moreover, we demonstrate the existence of strikingly significant changes in time delay due to relativistic effects despite Ne being a low-Z atom. This finding shows the possibility for utilizing time delay chronoscopy as a route towards experimental probing of relativistic interactions and the phases of individual transition matrix elements upon atomic photoionization of low-Z atoms. Finally, we develop a practical parametrization to model and explain the angle and energy variation of the autoionizing resonance time delay in the nonrelativistic limit. © 2019 American Physical Society.

Strong dependence of photoionization time delay on energy and angle in the neighborhood of Fano resonances

Wigner time delay in photodetachment from the 3p3/2 and 3p1/2 subshells of Cl- has been studied in the vicinity of the 2p3/2 and 2p1/2 thresholds, using the relativistic random phase approximation (RRPA). The results show time delay spectra dominated by many-body correlations along with very complicated dependence on the energy over a broad spectral range. In addition, the time delay spectra of the two spin-orbit split 3p subshells differ significantly from one another, thereby revealing the importance of relativistic effects even in the case of a low-Z system. © 2019 American Physical Society.

Dominance of correlation and relativistic effects on photodetachment time delay well above threshold

Dipole phase and photoelectron group delay in inner-shell photoionization

Journal	Data powered by TypesetPhysical Review A - Atomic, Molecular, and Optical Physics
Publisher	Data powered by TypesetAmerican Physical Society
ISSN	10502947
Open Access	Yes