Quantum dynamical investigation of product state distributions of the F + CH3OH → HF + CH3O reaction via photodetachment of the F−(HOCH3) anion

Abstract

The photodetachment of the F−(HOCH3) anion, which sheds light on the post-transition-state dynamics of the F + CH3OH → HF + CH3O reaction, is investigated using a reduced-dimensional quantum wave packet method on ab initio based potential energy surfaces for both the neutral and anionic species. The detachment of an electron in the anion precursor produces both bound and resonance species in a hydrogen-bonded potential well in the product channel, in qualitative agreement with the photoelectron-photofragment coincidence (PPC) spectrum. The measured photoelectron-photofragment coincidence spectroscopy is reproduced by the quantum calculations. Our results indicated that the HF product is vibrationally excited, while the OCH3 product is internally cold, thus providing unambiguous assignments of the experimental spectrum.

Advances and New Challenges to Bimolecular Reaction Dynamics Theory

“…For example, both the F + H 2 O → HF + OH and F + CH 3 OH → HF + CH 3 O reactions feature a low reaction barrier and both pre- and post-transition state wells. Like the F + H 2 reaction discussed above, well-defined resonances have been found in the product wells by photodetachment experiments ,− supported by quantum scattering calculations. ,, These resonances are all associated with a vibrationally excited HF product and thus are Feshbach in nature. The calculated state-to-state reaction probabilities of the F + H 2 O reaction have a rich oscillatory structure, which have been attributed to resonances in both the pre- and post-transition state wells. , Recent quantum scattering calculations demonstrated unequivocally that the post-transition state resonances have a strong influence on reactivity, as shown in Figure .…”

“…Like the F + H 2 reaction discussed above, welldefined resonances have been found in the product wells by photodetachment experiments 47,148−150 supported by quantum scattering calculations. 47,151,152 These resonances are all associated with a vibrationally excited HF product and thus are Feshbach in nature. The calculated state-to-state reaction probabilities of the F + H 2 O reaction have a rich oscillatory structure, which have been attributed to resonances in both the pre-and post-transition state wells.…”

Stereodynamical control of product branching in multi-channel barrierless hydrogen abstraction of CH3OH by F

“…This trend differs from our previous results for the thermal branching ratio. 47,48 As discussed in the ESI, † this difference is due to the fact that rotational excitation of methanol signicantly increases the reactivity of the (R1) reaction. A detailed analysis of mode specicity in this reaction will be discussed in a future publication.…”

“…In this work, we report an extensive theoretical investigation on the reaction dynamics of this multi-channel system, focusing on the reaction mechanism, as well as stereodynamics and its impact on the microcanonical branching ratio. These calculations were carried out on the globally accurate PES, which has been used successfully to simulate the photoelectron spectrum 43 and photoelectron-photoion coincidence spectrum of the F À (HOCH 3 ) anion 48 and to reproduce the experimental canonical rate coefficients and branching ratios well. 47 Here, integral and differential cross sections are computed for both product channels using QCT, which shed light on the mechanism of this multi-channel reaction.…”

Mode specificity of a multi-channel reaction prototype: F + CH3OH → HF + CH3O/CH2OH

“…Recently, a full-dimensional accurate PES, with both channels considered, was developed for it based on about 121,000 points calculated at the explicitly correlated (F12a) version of CCSD(T) with the AVDZ basis set [77]. The PES has been successfully employed in simulating the photoelectron spectrum [77] and photoelectron-photoion coincidence spectrum of the F − (HOCH 3 ) anion [79], and in reproducing the experimental thermal rate coefficients and branching ratios well [78].…”