HRTOF study of photoinitiated-reaction dynamics of small molecules.

摘要

Contributing to the field of molecular reaction dynamics, photodissociation of small molecules studied via high-n Rydberg time-of-flight (HRTOF) spectroscopy is presented. Product kinetic energy and angular distributions were analyzed to understand the internuclear forces governing photodissociation mechanisms in unimolecular decomposition and intracluster reactions. Chapter 1 introduces the field of molecular reaction dynamics and discusses the importance of the PES in terms of the complementary nature of experiment and theory. Photodissociation of HNCO by 193.3 nm radiation, in which the H + NCO(X 2Π) channel was observed, is presented in Chapter 2. In Chapters 3 and 4, the ultraviolet (UV) and double-resonance photodissociation of hydrogen halides are introduced and the concepts of spin-orbit branching ratio and molecular alignment are discussed. Photoinitiated unimolecular decomposition of acetylene and formaldehyde are presented in Chapters 5 and 6, respectively. The photophysics and photochemistry of weakly bound van der Waals clusters are studied in Chapters 7 and 8. In contrast to the case of HI dimer photodissociation, in which the possibility for signal contribution from higher-than-binary clusters can not be discounted, species-selection of (HCl)₂ is achieved via IR + UV double-resonance photodissociation. This is due to the photoexciation of the Q branch of the acceptor stretch of the dimer, whose frequency was identified through the application of cavity ringdown laser absorption spectroscopy (CRLAS).