Imaging the photochemistry of cyclobutanone using ultrafast electron diffraction: Experimental results
Abstract
We investigated the ultrafast structural dynamics of cyclobutanone following photoexcitation at λ = 200 nm using gas-phase megaelectronvolt ultrafast electron diffraction. Our investigation complements the simulation studies of the same process within this special issue. It provides information about both electronic state population and structural dynamics through well-separable inelastic and elastic electron scattering signatures. We observe the depopulation of the photoexcited S2 state of cyclobutanone with n3s Rydberg character through its inelastic electron scattering signature with a time constant of (0.29 ± 0.2) ps toward the S1 state. The S1 state population undergoes ring-opening via a Norrish Type-I reaction, likely while passing through a conical intersection with S0. The corresponding structural changes can be tracked by elastic electron scattering signatures. These changes appear with a delay of (0.14 ± 0.05) ps with respect to the initial photoexcitation, which is less than the S2 depopulation time constant. This behavior provides evidence for the ballistic nature of the ring-opening once the S1 state is reached. The resulting biradical species react further within (1.2 ± 0.2) ps via two rival fragmentation channels yielding ketene and ethylene, or propene and carbon monoxide. Our study showcases the value of both gas-phase ultrafast diffraction studies as an experimental benchmark for nonadiabatic dynamics simulation methods and the limits in the interpretation of such experimental data without comparison with such simulations.
Article Details
Journal Info
The Journal of Chemical Physics
American Institute of Physics
Authors (30)
A. E. Green
Stanford PULSE Institute, SLAC National Accelerator Laboratory 1 , 2575 Sand Hill Road, Menlo Park, California 94025,
Y. Liu
F. Allum
Stanford PULSE Institute, SLAC National Accelerator Laboratory 1 , 2575 Sand Hill Road, Menlo Park, California 94025,
M. Graßl
Stanford PULSE Institute, SLAC National Accelerator Laboratory 1 , 2575 Sand Hill Road, Menlo Park, California 94025,
P. Lenzen
Stanford PULSE Institute, SLAC National Accelerator Laboratory 1 , 2575 Sand Hill Road, Menlo Park, California 94025,
M. N. R. Ashfold
School of Chemistry, University of Bristol 5 , Bristol BS8 1TS,
S. Bhattacharyya
Linac Coherent Light Source, SLAC National Accelerator Laboratory 4 , 2575 Sand Hill Road, Menlo Park, California 94025,
X. Cheng
Linac Coherent Light Source, SLAC National Accelerator Laboratory 4 , 2575 Sand Hill Road, Menlo Park, California 94025,
M. Centurion
Department of Physics and Astronomy, University of Nebraska-Lincoln 6 , Lincoln, Nebraska 68588,
S. W. Crane
Department of Chemistry, Brown University 7 , Providence, Rhode Island 02912,
R. Forbes
Linac Coherent Light Source, SLAC National Accelerator Laboratory 4 , 2575 Sand Hill Road, Menlo Park, California 94025,
N. A. Goff
Department of Chemistry, Brown University 7 , Providence, Rhode Island 02912,
L. Huang
B. Kaufman
Linac Coherent Light Source, SLAC National Accelerator Laboratory 4 , 2575 Sand Hill Road, Menlo Park, California 94025,
M.-F. Kling
Stanford PULSE Institute, SLAC National Accelerator Laboratory 1 , 2575 Sand Hill Road, Menlo Park, California 94025,
P. L. Kramer
Linac Coherent Light Source, SLAC National Accelerator Laboratory 4 , 2575 Sand Hill Road, Menlo Park, California 94025,
H. V. S. Lam
James R. Macdonald Laboratory, Department of Physics, Kansas State University 3 , Manhattan, Kansas 66506,
K. A. Larsen
Linac Coherent Light Source, SLAC National Accelerator Laboratory 4 , 2575 Sand Hill Road, Menlo Park, California 94025,
R. Lemons
Linac Coherent Light Source, SLAC National Accelerator Laboratory 4 , 2575 Sand Hill Road, Menlo Park, California 94025,
M.-F. Lin
Linac Coherent Light Source, SLAC National Accelerator Laboratory 4 , 2575 Sand Hill Road, Menlo Park, California 94025,
A. J. Orr-Ewing
School of Chemistry, University of Bristol 5 , Bristol BS8 1TS,
D. Rolles
James R. Macdonald Laboratory, Department of Physics, Kansas State University 3 , Manhattan, Kansas 66506,
A. Rudenko
James R. Macdonald Laboratory, Department of Physics, Kansas State University 3 , Manhattan, Kansas 66506,
S. K. Saha
Department of Physics, Kansas State University 10 , Manhattan, Kansas 66506,
J. Searles
Department of Physics, Kansas State University 10 , Manhattan, Kansas 66506,
X. Shen
S. Weathersby
Linac Coherent Light Source, SLAC National Accelerator Laboratory 4 , 2575 Sand Hill Road, Menlo Park, California 94025,
P. M. Weber
Department of Chemistry, Brown University 7 , Providence, Rhode Island 02912,
H. Zhao
Department of Physics and Astronomy, University of Nebraska-Lincoln 6 , Lincoln, Nebraska 68588,
T. J. A. Wolf
Stanford PULSE Institute, SLAC National Accelerator Laboratory 1 , 2575 Sand Hill Road, Menlo Park, California 94025,