1. Photodissociation transition states characterized by chirped pulse millimeter wave spectroscopy.
- Author
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Prozument, Kirill, Baraban, Joshua H., Changala, P. Bryan, Park, G. Barratt, Shaver, Rachel G., Muenter, John S., Klippenstein, Stephen J., Chernyak, Vladimir Y., and Field, Robert W.
- Subjects
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FOURIER transform spectroscopy , *MILLIMETER waves , *FRANCK-Condon principle , *PHOTODISSOCIATION , *SPECTRUM analysis - Abstract
The 193-nm photolysis of CH2CHCN illustrates the capability of chirped-pulse Fourier transform millimeter-wave spectroscopy to characterize transition states. We investigate the HCN, HNC photofragments in highly excited vibrational states using both frequency and intensity information. Measured relative intensities of J = 1-0 rotational transition lines yield vibrational-level population distributions (VPD). These VPDs encode the properties of the parent molecule transition state at which the fragment molecule was born. A Poisson distribution formalism, based on the generalized Franck-Condon principle, is proposed as a framework for extracting information about the transition-state structure from the observed VPD. We employ the isotopologue CH2CDCN to disentangle the unimolecular 3-center DCN elimination mechanism from other pathways to HCN. Our experimental results reveal a previously unknown transition state that we tentatively associate with the HCN eliminated via a secondary, bimolecular reaction. [ABSTRACT FROM AUTHOR]
- Published
- 2020
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