Title: Imaging the photodissociation dynamics of internally excited ethyl radicals from high Rydberg states
Authors: Luis Rubio-Lago, David V. Chicharro, Sonia Marggi Poullain, Alexandre Zanchet, Greta Koumarianou, Pavle Glodic, Peter C. Samartzis, Alberto García-Vela, Luis Bañares
DOI: https://doi.org/10.1039/d2cp05082j
Date: 28/06/2023
Working Group: WG5
Grant Period: 2022-2026
Grant Period Goal (number): GAPG-6
Covered deliverables from the MoU (number): Accurate description of the intermolecular interaction between a molecule and its confining environment through modern first principles tools.
Countries involved: Spain, Greece
Number of female/young/ITC coauthors: Young female: 2
Abstract:The site-specific hydrogen-atom elimination mechanism previously reported for photoexcited ethyl radicals (CH3CH2) [D. V. Chicharro et al., Chem. Sci., 2019, 10, 6494] is interrogated in the photo- dissociation of the ethyl isotopologues CD 3CD2, CH3CD2 and CD3CH2 through the velocity map imaging (VMI) detection of the produced hydrogen- and deuterium-atoms. The radicals, generated in situ from photolysis of a precursor using the same laser pulse employed in their excitation to Rydberg states, decompose along the Ca-H/D and Cb-H/D reaction coordinates through coexisting statistical and site-specific mechanisms. The experiments are carried out at two excitation wavelengths, 201 and 193 nm. The comparison between both sets of results provides accurate information regarding the primary role in the site-specific mechanism of the radical internal reservoir. Importantly, at 193 nm excitation, higher energy dissociation channels (not observed at 201 nm) producing low-recoil H/D- atoms become accessible. High-level ab initio calculations of potential energy curves and the corresponding non-adiabatic interactions allow us to rationalize the experimental results in terms of competitive non-adiabatic decomposition paths. Finally, the adiabatic behavior of the conical inter- sections in the face of several vibrational modes – the so-called vibrational promoting modes – is discussed.
