Wigner time delay in photodetachment

Abstract

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 focusses 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 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 Cl − case; and absent in case of photoionization of Ar. The origin of these phenomenologies is explained and a prospectus for future work is presented.

Outer-shell photodetachment of Li− near inner-shell thresholds

“…Since negative ions, by their very nature, are much more highly-correlated than atoms, it is expected that these effects should be even more pronounced in negative ion photodetachment. This has been confirmed in a theoretical study of the photodetachment of Cl − [17] in which detachment-plus-excitation, a process known to be important in photodetachment, was not included.…”

A Tale of Two Representations: Energy and Time in Photoabsorption

“…On the other hand, the photoionization cross section for neutral atoms is a constant at threshold, independent of because of the long range Coulomb field seen by the escaping photoelectron. A recent detailed study by Manson and collaborators [23] through relativistic random phase calculations of Ar and its isoelectronic negative ion Cl − 3p → Ed, Es documents these features, and especially dramatically the sensitivity of the time delay τ . More so than the cross section σ, matrix element, or phase shift, it is τ that has the most pronounced structure in both Ar and Cl − around the Cooper minimum lying 45 eV above threshold.…”

Photoionization dynamics of Ar trapped in a fullerene anion: Coulomb confinement resonances in 2s subshell and its impact on the 3s subshell

“…These sophisticated experimental techniques enabled physicists to measure the time delay associated with photoionization. A large number of theoretical and experimental works have been done to study the attosecond chronography of free atoms [35][36][37][38][39][40][41][42][43][44][45]. Many theoretical works were performed for the time-delay associated with the atom confined inside fullerene [12,26,27,[46][47][48][49][50][51].…”