title: Time-resolved photoelectron imaging of ultrafast S2-->S1 internal conversion through conical intersection in pyrazine.
abstract: A nonadiabatic electronic transition through a conical intersection was studied by pump-probe photoelectron imaging spectroscopy with a 22 fs time resolution in the benchmark polyatomic molecule of pyrazine and deuterated pyrazine. The lifetimes of the S(2) state of pyrazine and deuterated pyrazine were determined to be 22+/-3 fs by the global fitting of the time-energy maps of photoelectron kinetic energy (PKE) distributions. The lifetime of S(3) was determined to be 40-43 fs. Two-dimensional maps of photoelectron distributions were obtained for time (t) and PKE, and individual PKE distributions upon ionization from S(2) and S(1) were extracted. Quantum beat with an approximately 50 fs period was observed after the S(2)-->S(1) internal conversion, which was attributed to the totally symmetric vibration nu(6a) in S(1).
authors.affiliation: CREST, Japan Science and Technology Agency, Sanbancho, Chiyoda-ku, Tokyo 102-0075, Japan.
authors.forename: Yoshi-Ichi
authors.initials: Y
authors.lastname: Suzuki
authors.forename: Takao
authors.initials: T
authors.lastname: Fuji
authors.forename: Takuya
authors.initials: T
authors.lastname: Horio
authors.forename: Toshinori
authors.initials: T
authors.lastname: Suzuki