Transient cars studies of styrene photophysics in the vapor phase
McCurdy, Keith Edward
Weisman, R. B.
Master of Arts
A computerized nanosecond time scale transient CARS spectrophotometer vas constructed to examine the vibrational spectroscopy and dynamics of molecular excited states in the gas phase. Ground and excited state spectroscopy, excited state kinetics, and ground state recovery kinetics of styrene vapor vere investigated using this apparatus. Previously unreported ground state (S) vibrational features of styrene vapor vere observed in both the CH and C=C stretching probe regions. Transient vibrational features attributable to the vibrationally relaxed state of styrene vere observed. Also, a vibrational hot band sequence involving the enharmonic coupling of the C=C phenyl ring stretch vith another mode of the molecule vas identified and a spectral assignment vas suggested. Kinetic modeling of observed transient features vith dual component decays suggested the formation of a product state assigned as T1, formed via intersystem crossing from and decaying into S. This vork represents the first report of a direct spectroscopic and kinetic identification of vibrations in an excited electronic state using transient CARS spectroscopy.