Observation of resonances in the transition state region of the F + NH3 reaction using anion photoelectron spectroscopy

Mark C Babin; Martin DeWitt; Jascha A Lau; Marissa L Weichman; Jongjin B Kim; Hongwei Song; Hua Guo; Daniel M Neumark

doi:10.1038/s41557-022-01100-1

Observation of resonances in the transition state region of the F + NH₃ reaction using anion photoelectron spectroscopy

Nat Chem. 2023 Feb;15(2):194-199. doi: 10.1038/s41557-022-01100-1. Epub 2022 Dec 12.

Authors

Mark C Babin^{1

2}, Martin DeWitt¹, Jascha A Lau¹, Marissa L Weichman^{1

3}, Jongjin B Kim^{1

4}, Hongwei Song⁵, Hua Guo⁶, Daniel M Neumark^{7

8}

Affiliations

¹ Department of Chemistry, University of California, Berkeley, CA, USA.
² Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA, USA.
³ Department of Chemistry, Princeton University, Princeton, NJ, USA.
⁴ KLA Corporation, Milpitas, CA, USA.
⁵ State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Innovation Academy for Precision Measurement Science and Technology, Chinese Academy of Sciences, Wuhan, China. hwsong@wipm.ac.cn.
⁶ Department of Chemistry and Chemical Biology, University of New Mexico, Albuquerque, NM, USA.
⁷ Department of Chemistry, University of California, Berkeley, CA, USA. dneumark@berkeley.edu.
⁸ Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA. dneumark@berkeley.edu.

PMID: 36509851
DOI: 10.1038/s41557-022-01100-1

Abstract

The transition state of a chemical reaction is a dividing surface on the reaction potential energy surface (PES) between reactants and products and is thus of fundamental interest in understanding chemical reactivity. The transient nature of the transition state presents challenges to its experimental characterization. Transition-state spectroscopy experiments based on negative-ion photodetachment can provide a direct probe of this region of the PES, revealing the detailed vibrational structure associated with the transition state. Here we study the F + NH₃ → HF + NH₂ reaction using slow photoelectron velocity-map imaging spectroscopy of cryogenically cooled FNH₃^- anions. Reduced-dimensionality quantum dynamical simulations performed on a global PES show excellent agreement with the experimental results, enabling the assignment of spectral structure. Our combined experimental-theoretical study reveals a manifold of vibrational Feshbach resonances in the product well of the F + NH₃ PES. At higher energies, the spectra identify features attributed to resonances localized across the transition state and into the reactant complex that may impact the bimolecular reaction dynamics.

Abstract

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