Photodissociation dynamics of ozone using Raman excitation profiles (REP's)
Lotfi, Erik Siavash
Kinsey, James L.
Doctor of Philosophy
Because of the environmental importance, ozone has long been one of the prominent research topics in the scientific community. Surprisingly, in spite of all the research, the UV photodissociation dynamics of ozone has not been completely understood yet. More specifically, the origin of the small structural features overlapping the broad-band feature in the UV absorption spectrum of ozone still remains a mystery. However, theoretical calculations done in our lab predict, subject to UV radiation, great majority of ozone molecules fall apart in roughly 6 femtoseconds while a very minute portion, about 1% corresponding to small structural features take much longer to dissociate (up to 150 femtoseconds). Even with the fastest lasers currently available, it would not be possible to learn about the photodissociation dynamics of ozone using Femtosecond chemistry. However, a unique technique called continuous-scan Raman Excitation Profiles developed and tested on iodobenzene in our lab has proven to be a powerful method in learning about extremely fast dissociating processes such as ozone. One of the features that make REP's a powerful tool is that, it provides valuable knowledge of time domain behavior based on only the intensity and frequency of the emitted photons. However, primarily because of its extremely low photon yield, one must overcome several significant and challenging experimental problems associated with the apparatus before achieving any reliable ozone REPs. The main objective of this thesis is to demonstrate how these problems were solved and to discuss and analyze some recently obtained preliminary data to be the guide for those pursuing full-scale ozone REP'S in the future.
Physical chemistry; Atmospheric sciences