Seminar: Jakub Benda (Charles University, Prague); Wed 8 December

Last updated November 29, 2021 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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