Theory on polarization-averaged core-level molecular-frame photoelectron angular distributions: II. Extracting the X-ray induced fragmentation dynamics of carbon monoxide dication from forward and backward intensities

Fukiko Ota (1) , Keisuke Hatada (2) , Didier Sébilleau (2) , Kiyoshi Ueda (3) , Kaoru Yamazaki (4)

1 University of Toyama
2 IPR - Institut de Physique de Rennes
3 Tohoku University [Sendai]
4 RIKEN RAP - RIKEN Center for Advanced Photonics [Wako]

Recent developments in high repetition-rate X-ray free electron lasers (XFELs) such as the European XFEL and the LSCS-II, combined with coincidence measurements at the COLTRIMS--Reaction Microscope, is now opening a door to realize the long-standing dream to create molecular movies of photo-induced chemical reactions in gas-phase molecules. In this paper, we propose a new theoretical method to experimentally visualize the dissociation of diatomic molecules via time-resolved polarization-averaged molecular-frame photoelectron angular distributions (PA-MFPADs) measurements using the COLTRIMS--Reaction Microscope and the two-color XFEL pump-probe set-up. We used first and second order scattering theory within the Muffin-tin approximation, which is valid for a sufficiently high kinetic energy of photoelectron, typically above 100 eV, and for long bond lengths. This leads to a simple EXAFS-type formula for the forward and backward scattering peaks in the PA-MFPADs structure. This formula relies only on three semi-empirical parameters obtainable from the time-resolved measurements. It can be used as a "bond length ruler" on experimental results. The accuracy and applicability of the new ruler equation are numerically examined against the PA-MFPADs of CO2+ calculated with Full-potential multiple scattering theory as a function of the C-O bond length reported in the preceding work [1]. The bond lengths retrieved from the the PA-MFPADs via our EXAFS-like formula coincide within an accuracy of 0.1 Å with the original C-O bond lengths used in the reference ab-initio PA-MFPADs. We expect time-resolved PA-MFPADs to become a new attractive tool to make molecular movies visualizing intramolecular reactions.

Domains: Physics [physics]

Fukiko Ota, Keisuke Hatada, Didier Sébilleau, Kiyoshi Ueda, Kaoru Yamazaki. Theory on polarization-averaged core-level molecular-frame photoelectron angular distributions: II. Extracting the X-ray induced fragmentation dynamics of carbon monoxide dication from forward and backward intensities. Journal of Physics B: Atomic, Molecular and Optical Physics, 2021, 54 (8), pp.084001. ⟨10.1088/1361-6455/abcfd8⟩. ⟨hal-03103805⟩