Seminar: Jakub Benda (Charles University, Prague); Wed 8 December
Last updated January 6, 2022 by Dermot Green
8 December 2021, 3pm
Location: MS Teams online seminar
Multi-photon ionisation of molecules and RABITT in R-matrix method
Processes involving ionisation of molecules by absorption of multiple photons
proved very useful for experimental analysis of electronic structure and for
measurement of intrinsic photoionisation delays. Attosecond streaking as well
as the RABITT interference experiment now serve as widespread tools for
inspection of attosecond electron dynamics.
In this seminar I will present our on-going theoretical work on above-
threshold multi-photon ionisation of molecules. I will discuss the extension
of the flexible and widely used one-photon R-matrix method [1] to absorption
of arbitrary order [2]. The method allows us to compute time-independent
ionisation amplitudes for all pathways participating e.g. in the RABITT
measurements, including its higher-order variants. We can then predict the
measurable sideband delays without resorting to the frequently used, but
incomplete, asymptotic approaches [3]. At the same time, the time-independent
theory is typically computationally more efficient than fully general time-
dependent methods [4].
As illustration of the capabilities of the method I will present and compare
to experiments averaged laboratory-frame time delays for several diatomic and
polyatomic molecules. Finally, I will discuss some specific interesting
aspects revealed by the theory, related to the partial wave interference and
to the effect the channel coupling has on the photoionisation delays.
[1] Benda et al., Phys. Rev. A 102, 052826 (2020)
[2] Benda & Mašín, Sci. Rep. 11, 11686 (2021)
[3] Baykusheva & Wörner, J. Chem. Phys. 146, 124306 (2017)
[4] Brown et al., Comput. Phys. Commun. 250, 107062 (2020)
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