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High-Resolution Photoelectron Spectroscopy of the Pyridinide Isomers

preprint
submitted on 25.07.2019 and posted on 26.07.2019 by Jessalyn DeVine, Mark Babin, Katherine Blackford, Daniel Neumark
Isomer-specific, high-resolution photoelectron spectra of cryogenically-cooled pyridinide anions obtained using slow photoelectron velocity-map imaging are presented. New vibrational structure in the detachment spectrum of para-pyridinide is resolved, and the spectra of meta- and ortho-pyridinide are reported for the first time. These spectra yield electron affinities of 1.4797(5), 1.4473(5), and 0.8669(7) eV for the para-, meta- and ortho-pyridyl radicals, respectively, as well as a number of vibrational frequencies for each neutral isomer. While most of the resolved structure in all three spectra is readily assigned by comparison to B3LYP/6-311+G* Franck-Condon simulations, the para-pyridinide spectrum shows newly-resolved fine structure attributed to anharmonic coupling within the vibrational manifold of the corresponding neutral radical. Isomeric trends in the photoelectron angular distributions are rationalized by approximating the detached anion orbitals as superpositions of s, p, and d-like hydrogenic orbitals, based on an application of Sanov’s generalized mixing model [J. Chem. Phys. 141, 124312 (2014)]. The presented experimental and theoretical results are used to address the relative energies of the anion and neutral isomers, as well as the site-specific bond dissociation energies of pyridine.

History

Email Address of Submitting Author

jdevine@berkeley.edu

Institution

UC Berkeley

Country

United States

ORCID For Submitting Author

0000-0003-0091-4286

Declaration of Conflict of Interest

No conflict of interest

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in The Journal of Chemical Physics

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