title: Cyclohexadiene Revisited: A Time-Resolved Photoelectron Spectroscopy and ab Initio Study.
abstract: We have reinvestigated the excited state dynamics of cyclohexa-1,3-diene (CHD) with time-resolved photoelectron spectroscopy and fewest switches surface hopping molecular dynamics based on linear response time-dependent density functional theory after excitation to the lowest lying ππ* (1B) state. The combination of both theory and experiment revealed several new results: First, the dynamics progress on one single excited state surface. After an incubation time of 35 ± 10 fs on the excited state, the dynamics proceed to the ground state in an additional 60 ± 10 fs, either via a conrotatory ring-opening to hexatriene or back to the CHD ground state. Moreover, ring-opening predominantly occurs when the wavepacket crosses the region of strong nonadiabatic coupling with a positive velocity in the bond alternation coordinate. After 100 fs, trajectories remaining in the excited state must return to the CHD ground state. This extra time delay induces a revival of the photoelectron signal and is an experimental confirmation of the previously formulated model of two parallel reaction channels with distinct time constants. Finally, our simulations suggest that after the initially formed cis-Z-cis HT rotamer the trans-Z-trans isomer is formed, before the thermodynamical equilibrium of three possible rotamers is reached after 1 ps.
authors.affiliation: Department of Chemical Physics, AlbaNova University Centre, Stockholm University , Roslagstullsbacken 21, 106 91 Stockholm, Sweden.
authors.forename: Oliver
authors.initials: O
authors.lastname: Schalk
authors.affiliation: Department of Chemical Physics, AlbaNova University Centre, Stockholm University , Roslagstullsbacken 21, 106 91 Stockholm, Sweden.
authors.forename: Ting
authors.initials: T
authors.lastname: Geng
authors.affiliation: Department of Chemistry and Biochemistry, California State University, Long Beach , 1250 Bellflower Boulevard, Long Beach, California 90840-9507, United States.
authors.forename: Travis
authors.initials: T
authors.lastname: Thompson
authors.affiliation: Department of Chemistry and Biochemistry, California State University, Long Beach , 1250 Bellflower Boulevard, Long Beach, California 90840-9507, United States.
authors.forename: Noel
authors.initials: N
authors.lastname: Baluyot
authors.affiliation: Department of Chemical Physics, AlbaNova University Centre, Stockholm University , Roslagstullsbacken 21, 106 91 Stockholm, Sweden.
authors.forename: Richard D
authors.initials: RD
authors.lastname: Thomas
authors.affiliation: Department of Chemistry and Biochemistry, California State University, Long Beach , 1250 Bellflower Boulevard, Long Beach, California 90840-9507, United States.
authors.forename: Enrico
authors.initials: E
authors.lastname: Tapavicza
authors.affiliation: Department of Chemical Physics, AlbaNova University Centre, Stockholm University , Roslagstullsbacken 21, 106 91 Stockholm, Sweden.
authors.forename: Tony
authors.initials: T
authors.lastname: Hansson