Study Of Nonadiabatic Dynamics Of Nitrogen-Containing Aromatic Compounds

Reactions of molecular with laser often involve many electronically excited state nonadiabatic dynamics process. These nonadiabatic dynamic processes are the primary steps in the photochemistry of many polyatomic systems, involving as well as in photobiological processes such as vision, photosynthesis, and DNA damage, and underlie many concepts in molecular electronics. These nonadiabatic dynamic processes play an important role in photophysics, photochemistry, life science and environmental science. The nonadiabatic deactivation processes of electronically excited molecules including photodissociation, isomerization, internal conversion, intersystem crossing, internal vibrational energy redistribution and so on. All these nonadiabatic process are achieved in ultrafast time scale. The femtosecond time-resolved photoelectron imaging technique is extremely useful in this regard, since it provides the most sensitive and versatile means to probe these ultrafast nonadiabatic processes through the observation of time-dependent photoelectron energy and angular distributions. In this dissertation, three types of Nitrogen-containing aromatic compounds and Thionyl chloride are selected and these nonadiabatic deactivation processes are investigated. The dissertation is organized as follows:In the first part, Ultrafast dynamics of excited states of2-picoline have been studied using femtosecond time-resolved photoelectron imaging coupled with time-resolved mass spectroscopy. The internal conversion of2-picoline from the S2state to the vibrationally excited S1state is observed in real time. The time scale of internal conversion from the S2to S1state was determined to be937fs. The secondarily populated high vibronic S1state deactivates further to the So state in time scale of-3.01ps. Photoelectron energy and angular distributions reveal the feature of ionization from the singlet3p Rydberg states. In addition, variation of time-dependent anisotropy parameters indicates the rotational coherence of the molecule.In the second part, nonadiabatic dynamics process on the S2state and3s Rydberg state of3-picoline was investigated. The internal conversion from the S2state to the vibrationally hot S1state is directly observed in real time. Photoelectron energy and angular distributions reveal the feature of ionization from the singlet3p Rydberg states. We also determined the life time of3s Rydberg state of3-picoline is62fs. It was suggested that3s Rydberg state deactivate to the ground state by internal conversion.In the third part, nonadiabatic dynamic process of excited aniline wan studied. After population, S2state may decay to the S1state by IC in a time scale of205fs. S1state populated by coupling to S2/S3and to the ground state So with the time scale of13.5ps. We suggest the Rydberg characteristic S2state lies at37104±100cm-1.We also observed the internal vibrational energy redistribution process on the S1potential energy surface.In the forth part, Photodissociation of Thionyl chloride at235nm has been studied using femtosecond time-resolved mass spectroscopy. There body dissociation process has been investigated in thionyl chloride. Most interestingly, concerted three body dissociation process in a time scale of69fs was observed.