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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