TY - JOUR
T1 - Photodissociation transition states characterized by chirped pulse millimeter wave spectroscopy
AU - Prozument, Kirill
AU - Baraban, Joshua H.
AU - Bryan Changala, P.
AU - Barratt Park, G.
AU - Shaver, Rachel G.
AU - Muenter, John S.
AU - Klippenstein, Stephen J.
AU - Chernyak, Vladimir Y.
AU - Field, Robert W.
N1 - Publisher Copyright: © 2020 National Academy of Sciences. All rights reserved.
PY - 2020/1/7
Y1 - 2020/1/7
N2 - 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.
AB - 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.
KW - Chirped-pulse millimeter-wave spectroscopy
KW - Photolysis
KW - Transition state
KW - Vibrational population distribution
KW - Vibrational satellites
UR - http://www.scopus.com/inward/record.url?scp=85077506538&partnerID=8YFLogxK
U2 - https://doi.org/10.1073/pnas.1911326116
DO - https://doi.org/10.1073/pnas.1911326116
M3 - Article
C2 - 31852828
SN - 0027-8424
VL - 117
SP - 146
EP - 151
JO - Proceedings of the National Academy of Sciences of the United States of America
JF - Proceedings of the National Academy of Sciences of the United States of America
IS - 1
ER -