Spectroscopic characterization of isomerization transition states

• Main Authors: Mellau, Georg Ch (Author), Stanton, John F. (Author), Merer, Anthony J. (Author), Baraban, Joshua Herschel (Contributor), Changala, P. Bryan (Contributor), Field, Robert W (Contributor)
• Other Authors: Massachusetts Institute of Technology. Department of Chemistry (Contributor)
• Format: Article
• Language: English
• Published: American Association for the Advancement of Science (AAAS), 2017-03-02T21:43:26Z.
• Subjects: Article
• Online Access: Get fulltext

Transition state theory is central to our understanding of chemical reaction dynamics. We demonstrate a method for extracting transition state energies and properties from a characteristic pattern found in frequency-domain spectra of isomerizing systems. This pattern-a dip in the spacings of certain barrier-proximal vibrational levels-can be understood using the concept of effective frequency, ω[superscript]eff. The method is applied to the cis-trans conformational change in the S[subscript 1] state of C[subscript 2]H[Subscript 2] and the bond-breaking HCN-HNC isomerization. In both cases, the barrier heights derived from spectroscopic data agree extremely well with previous ab initio calculations. We also show that it is possible to distinguish between vibrational modes that are actively involved in the isomerization process and those that are passive bystanders.
National Science Foundation (U.S.) (NSF Graduate Research Fellowship DGE 1144083)
Alexander von Humboldt-Stiftung (Feodor Lynen fellowship)
United States. Department of Energy (Grant DE-FG0287ER136)