title: Spectroscopy and femtosecond dynamics of the ring opening reaction of 1,3-cyclohexadiene.
abstract: The early stages of the ring opening reaction of 1,3-cyclohexadiene to form its isomer 1,3,5-hexatriene, upon excitation to the ultrashort-lived 1 1B2 state, were explored. A series of one-color two-photon ionization/photoelectron spectra reveal a prominent vibrational progression with a frequency of 1350 cm(-1), which is interpreted in a dynamical picture as resulting from the ultrafast wave packet dynamics associated with the ring opening reaction. Photoionization in two-color three-photon and one-color four-photon ionization schemes show an ionization pathway via the same ultrashort-lived 1 1B2 state, and in addition, a series of Rydberg states with quantum defects of 0.93, 0.76, and 0.15, respectively. Using those Rydberg states as probes for the reaction dynamics in a time-resolved pump-probe experiment provides a direct observation of the elusive 2 1A1 state that has been implicated as an intermediate step between the initially excited 1 1B2 state and the ground electronic state. The rise and decay times for the 2 1A1 state were found to be 55 and 84 fs, respectively.
authors.affiliation: Department of Physics and Astronomy, College of Charleston, Charleston, South Carolina 29424, USA.
authors.forename: Narayanan
authors.initials: N
authors.lastname: Kuthirummal
authors.forename: Fedor M
authors.initials: FM
authors.lastname: Rudakov
authors.forename: Conor L
authors.initials: CL
authors.lastname: Evans
authors.forename: Peter M
authors.initials: PM
authors.lastname: Weber