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Title: Excited state non-adiabatic dynamics of the smallest polyene, trans 1,3-butadiene. I. Time-resolved photoelectron-photoion coincidence spectroscopy

The ultrafast excited state dynamics of the smallest polyene, trans-1,3-butadiene, were studied by femtosecond time-resolved photoelectron-photoion coincidence (TRPEPICO) spectroscopy. The evolution of the excited state wavepacket, created by pumping the bright 1B u (ππ*) electronic state at its origin of 216 nm, is projected via one- and two-photon ionization at 267 nm onto several ionization continua. The results are interpreted in terms of Koopmans’ correlations and Franck-Condon factors for the excited and cationic states involved. The known predissociative character of the cation excited states is utilized to assign photoelectron bands to specific continua using TRPEPICO spectroscopy. This permits us to report the direct observation of the famously elusive S 1(2 1A g) dark electronic state during the internal conversion of trans 1,3-butadiene. Our phenomenological analysis permits the spectroscopic determination of several important time constants. We report the overall decay lifetimes of the 1 1B u and 2 1A g states and observe the re-appearance of the hot ground state molecule. We argue that the apparent dephasing time of the S 2(1 1B u) state, which leads to the extreme breadth of the absorption spectrum, is principally due to large amplitude torsional motion on the 1B u surface in conjunction withmore » strong non-adiabatic couplings via conical intersections, whereupon nuclear wavepacket revivals to the initial Franck-Condon region become effectively impossible. Lastly, in Paper II [W. J. Glover et al., J. Chem. Phys. 148, 164303 (2018)], ab initio multiple spawning is used for on-the-fly computations of the excited state non-adiabatic wavepacket dynamics and their associated TRPEPICO observables, allowing for direct comparisons of experiment with theory.« less
Authors:
 [1] ; ORCiD logo [2] ;  [2] ; ORCiD logo [3] ; ORCiD logo [3] ;  [4] ; ORCiD logo [1] ; ORCiD logo [3] ;  [5]
  1. National Research Council (CNR), Ottawa, ON (Canada); Univ. of Ottawa, of Ottawa, ON (Canada). Dept. of Chemistry
  2. National Research Council (CNR), Ottawa, ON (Canada)
  3. SLAC National Accelerator Lab., Menlo Park, CA (United States). Photon Ultrafast Laser Science and Engineering Inst. (PULSE); SLAC National Accelerator Lab., Menlo Park, CA (United States)
  4. Ulsan National Inst. of Science and Technology, Ulju-gun, Ulsan (South Korea)
  5. National Research Council (CNR), Ottawa, ON (Canada); Univ. of Ottawa, of Ottawa, ON (Canada). Dept. of Chemistry; Univ. of Ottawa, of Ottawa, ON (Canada). Dept. of Physics
Publication Date:
Grant/Contract Number:
AC02-76SF00515
Type:
Accepted Manuscript
Journal Name:
Journal of Chemical Physics
Additional Journal Information:
Journal Volume: 148; Journal Issue: 16; Journal ID: ISSN 0021-9606
Publisher:
American Institute of Physics (AIP)
Research Org:
SLAC National Accelerator Lab., Menlo Park, CA (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22). Chemical Sciences, Geosciences & Biosciences Division; USDOE
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
OSTI Identifier:
1438815
Alternate Identifier(s):
OSTI ID: 1434394