Quantum state and conformer specific molecular photoionization and photodissociation

Abstract

Chemical properties at the molecular level deserve to be investigated thoroughly for the advance of fundamental science as well as for applications in our daily lives, which are intrinsically dependent on the molecular potential energy surfaces (PESs). Generally, the Born-Oppenheimer approximation has provided a reasonable description for PESs, but they are unsuitable for the relatively complex molecular systems involved in electronic excited states. Accordingly, in the field of chemistry, even for complicated molecules, in addition to the fundamental goals, it is an ultimate dream of physical chemists to probe the quantum state more exactly and thus control chemical dynamics over the range from the neutral ground (S0) to the cationic excited (D1) states. There have been enormous efforts devoted to accomplish this, and among two main streams in this research, one is to develop experimental tools to dissect the complex quantum states into smaller pieces associated with specific chemical reactions through state-to-state measurements. On the other hand, physical chemists have concentrated on the photoionization and photodissociation studies of molecules to provide valuable chemical properties as the most fundamental processes. Quantum state and conformer specific molecular photoionization and photodissociation make up the experimental field of physical chemistry where the above two streams meet and must be reconciled. In this dissertation, successfully conducted corresponding studies are described, and simultaneously it provides precise measurements of molecular chemical properties through existing or newly developed experimental techniques, namely, using the mass-analyzed threshold ionization (MATI) spectroscopy with VUV photon energies, ionization energies and vibronic structures in the cationic ground state (D0) was determined exactly to unveil molecular structural changes upon ionization. From this, the ionization processes were compared between oxazole and ...