Visualizing competing intersystem crossing and internal conversion with a complementary measurement.
J Chem Phys
; 144(8): 084201, 2016 Feb 28.
Article
em En
| MEDLINE
| ID: mdl-26931694
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 T3âS2 and internal conversion S1âS2 are attributed to the deactivation of the S2 state. A lifetime of â¼50 fs for the initially excited S2 state, of â¼276 fs for the secondary populated S1 state, and of 5.76 ps for the T3 state is inferred.
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01-internacional
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MEDLINE
Idioma:
En
Ano de publicação:
2016
Tipo de documento:
Article