Imaging rehybridization dynamics into the pericyclic minimum of an electrocyclic reaction in real-time

ORAL

Abstract

We investigate structural dynamics of wavepacket relaxation along pericyclic transition states with a combination of ultrafast electron diffraction (UED) and ab-initio multiple spawning (AIMS) excited state wavepacket simulation. We focused this study on the molecular system alpha-terpinene (αTP, C10H16), which is a derivative of 1,3-Cyclohexidiene (CHD, C6H8) by the addition of two substituents, a methyl group and an isopropyl group (replacing the relevant hydrogen atoms). We took the advantage that αTP does not qualitatively alter the photochemical dynamics in comparison of CHD, but the carbons in the substituent groups act as “reporter” atoms in adding signatures of carbon-carbon bond distance to the time-dependent pair distribution functions (PDFs), which were missing in our previous study of CHD. We observed real-time signatures of the structural evolution towards the pericyclic minimum in both measurements and simulations. Detailed analyses from the simulated wavepacket revealed the signatures to be due to the hybridization change from sp3 to sp2 configurations largely happening in the excited state prior to bond dissociation to the ring-opening which takes place directly after the internal conversion to the ground state. Our combined experimental and theoretical approaches reflected structural dynamics leading to overlap of the conjugated π-system with the σ-bond prior to its dissociation. In addition, this work also questions the simple picture of the conrotatory motion predicted by the famous Woodward-Hoffmann rules.

*This work was supported by the AMOS program within the DOE Office of Science, Basic Energy Sciences, Chemical Sciences, Geosciences, and Biosciences Division.The experiement was supported under DOE with contracts DE-AC02-05-CH11231 and DE-AC02-76SF00515.

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Presenters

  • Yusong Liu

    • Stanford PULSE Institute
    • State Univ of NY - Stony Brook

Authors

  • Yusong Liu

    • Stanford PULSE Institute
    • State Univ of NY - Stony Brook

  • David Sanchez

    • Lawrence Livermore National Laboratory

  • Matthew Ware

    • Stanford PULSE Institute

  • Elio Champenios

    • Stanford PULSE Institute

  • Jie Yang

    • Tsinghua University
    • Department of Engineering Physics, Tsinghua University, Beijing 100084, China

  • Pedro Nunes

    • University of Nebraska, Lincoln
    • Department of Physics and Astronomy, University of Nebraska, 855 N 16th Street, Lincoln, NE 68588, USA

  • Martin Centurion

    • University of Nebraska - Lincoln

  • James P Cryan

    • SLAC National Lab
    • LCLS, SLAC National Accelerator Laboratory, Menlo Park, CA, USA
    • Stanford PULSE Institute, SLAC National Lab; LCLS, SLAC National Lab
    • SLAC National Accelerator Laboratory

  • Ruaridh Forbes

    • SLAC - Natl Accelerator Lab
    • Stanford PULSE Institute, SLAC National Accelerator Laboratory
    • Stanford PULSE Institute, SLAC National Lab; LCLS, SLAC National Lab; Department of Physics, Stanford University
    • SLAC National Accelerator Laboratory

  • Ming-Fu Lin

    • SLAC - Natl Accelerator Lab
    • LCLS, SLAC National Accelerator Laboratory, Menlo Park, CA, USA

  • Sajib Kumar Saha

    • University of Nebraska - Lincoln

  • Michael Minitti

    • SLAC National Accelerator Lab

  • Xijie Wang

    • SLAC National Lab
    • SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, USA

  • Markus Guehr

    • Universität Potsdam
    • Institut fur Physik and Astronomie, Universitat Potsdam, Potsdam, 14476 Germany

  • Todd J Martinez

    • Stanford Univ

  • Thomas J Wolf

    • SLAC - Natl Accelerator Lab
    • LCLS, SLAC National Accelerator Laboratory, Menlo Park, CA, USA