title: Visualizing competing intersystem crossing and internal conversion with a complementary measurement.
abstract: A complementary measurement method based on a home-built double-sided velocity map imaging setup is introduced. This method can simultaneously obtain time-resolved photoelectron imaging and fragment ion imaging. It has been successfully applied to investigate the ultrafast dynamics of the second singlet electronically excited state (S2) in m-xylene. Time-resolved photoelectron and ion signals derived from the initial populated S2 state are tracked following two-photon absorption of a pump pulse. Time-of-flight mass spectra (TOFMS) show that there are dominant parent ions and one fragment ions with methyl loss during such a process. According to the measured photoelectron images and fragment ions images, transient kinetic energy distributions and angular distributions of the generated photoelectrons and fragments are obtained and analyzed. Compared to stand-alone photoelectron imaging, the obtained fragment ion imaging is powerful for further understanding the mechanisms especially when the dissociation occurs during the pump-probe ionization. Two competing channels intersystem crossing T3←S2 and internal conversion S1←S2 are attributed to the deactivation of the S2 state. A lifetime of ∼50 fs for the initially excited S2 state, of ∼276 fs for the secondary populated S1 state, and of 5.76 ps for the T3 state is inferred.
authors.affiliation: School of Physics and Optoelectronic Engineering, Nanjing University of Information Science & Technology, Nanjing 210044, People's Republic of China.
authors.forename: Yuzhu
authors.initials: Y
authors.lastname: Liu
authors.affiliation: Paul Scherrer Institute, 5232 Villigen, Switzerland.
authors.forename: Thomas
authors.initials: T
authors.lastname: Gerber
authors.affiliation: Henan Normal University, Xinxiang 453007, People's Republic of China.
authors.forename: Chaochao
authors.initials: C
authors.lastname: Qin
authors.affiliation: School of Physics and Optoelectronic Engineering, Nanjing University of Information Science & Technology, Nanjing 210044, People's Republic of China.
authors.forename: Feng
authors.initials: F
authors.lastname: Jin
authors.affiliation: Paul Scherrer Institute, 5232 Villigen, Switzerland.
authors.forename: Gregor
authors.initials: G
authors.lastname: Knopp