O: Comparing Theory and Experiment in Multiphoton Photoionization*

We present the modeling of multiphoton photoionization dynamics in molecules, based on interference between multiple photoionization pathways within the framework of time-dependent perturbation theory (TDPT) at the Hartree-Fock level. For the achiral molecule CF₄, we investigated multiphoton photoionization using the reconstruction of attosecond beating by interference of two-photon transitions (RABBIT) scheme. We computed differential photoelectron spectra and compared the results with experimental data [1]. For the chiral molecule C₃H₆O, we calculated RABBIT-photoelectron circular dichroism (PECD) and found that our results closely matched experimental observations [2]. In our study, we addressed the challenge of accurately modeling continuum-continuum interactions in the multiphoton photoionization process based on an interferometric scheme by introducing modifications to ab initio quantum chemistry methods. Specifically, we examined the influence of quantum chemical basis sets on the accuracy of these interactions. Standard Gaussian basis sets were augmented with a large number of diffuse functions to improve the representation of continuum states and resolve discrepancies observed in the multiphoton RABBIT-PECD calculations [3]. The use of highly augmented Gaussian basis sets at the Hartree-Fock level provided deeper insights into molecular orbital distributions, significantly improving the accuracy of orbital descriptions and enabling a more precise treatment of continuum interactions.

[1]. Saijoscha Heck et al., Sci. Adv.7,eabj8121(2021).DOI:10.1126/sciadv.abj8121

[2]. Meng Han et al., (Submitted for review)

[3]. R. E. Goetz et al., arXiv:2104.07522v2 [physics.atom-ph]