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Journal Article

Photodissociation transition states characterized by chirped pulse millimeter wave spectroscopy.

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Park,  G. B.
Department of Dynamics at Surfaces, MPI for Biophysical Chemistry, Max Planck Society;

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(Supplementary material), 83KB

Citation

Prozument, K., Baraban, J. H., Changala, P. B., Park, G. B., Shaver, R. G., Muenter, J. S., et al. (2020). Photodissociation transition states characterized by chirped pulse millimeter wave spectroscopy. Proceedings of the National Academy of Sciences of the United States of America, 117(1), 146-151. doi:10.1073/pnas.1911326116.


Cite as: http://hdl.handle.net/21.11116/0000-0005-8472-5
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.