title: Structural dynamics of photochemical reactions probed by time-resolved photoelectron spectroscopy using high harmonic pulses.
abstract: Femtosecond ring-opening dynamics of 1,3-cyclohexadiene (CHD) in gas phase upon two-photon excitation at 400 nm (=3.1 eV) was investigated by time-resolved photoelectron spectroscopy using 42 nm (=29.5 eV) high harmonic photons probing the dynamics of the lower-lying occupied molecular orbitals (MOs), which are the fingerprints of the molecular structure. After 500 fs, the photoelectron intensity of the MO constituting the C[double bond, length as m-dash]C sigma bond (σC[double bond, length as m-dash]C) of CHD was enhanced, while that of the MO forming the C-C sigma bond (σCC) of CHD was decreased. The changes in the photoelectron spectra suggest that the ring of CHD opens to form a 1,3,5-hexatriene (HT) after 500 fs. The dynamics of the σC[double bond, length as m-dash]Cand σCCbands between 200 and 500 fs reflects the ring deformation to a conical intersection between the 21A and 11A potential energy surfaces prior to the ring-opening reaction.
authors.affiliation: Department of Applied Physics, Faculty of Engineering, Hokkaido University, Kita 13 Nishi 8, Kita-ku, Sapporo 060-8628, Japan. sekikawa@eng.hokudai.ac.jp.
authors.forename: Ryo
authors.initials: R
authors.lastname: Iikubo
authors.affiliation: Department of Applied Physics, Faculty of Engineering, Hokkaido University, Kita 13 Nishi 8, Kita-ku, Sapporo 060-8628, Japan. sekikawa@eng.hokudai.ac.jp.
authors.forename: Taro
authors.initials: T
authors.lastname: Sekikawa
authors.affiliation: Department of Chemistry, Faculty of Science, Hokkaido University, Kita 10 Nishi 8, Kita-ku, Sapporo 060-0810, Japan.
authors.forename: Yu
authors.initials: Y
authors.lastname: Harabuchi
authors.affiliation: Department of Chemistry, Faculty of Science, Hokkaido University, Kita 10 Nishi 8, Kita-ku, Sapporo 060-0810, Japan.
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Taketsugu