Studies in Gas Phase Nonlinear Laser Spectroscopy and Laser Assisted Processes at the Gas-Surface Interface 251 views

More than 60 years following the demonstration of the first laser it remains one of the most valuable tools for modern scientific investigation. In recent years, the development of new techniques and instrumentation have led to improvements in measuring absolute frequencies and phases of optical waves, increasingly short laser pulses or narrow continuous-wave line widths. These techniques and more have led to advances in the understanding of the energetics, kinetics, and dynamics of chemical processes and all while enhancing both sensitivity and selectivity. Here, a portion of my graduate work is described by three separate projects where laser spectroscopy techniques were employed. First, the development of a high-resolution absorption spectrometer for detection of gas phase mercury at 405 nm. The lowest energy ground-state transition for mercury is at 254 nm. Lower energy excitation is achieved via pre-excitation of the ground state, followed by promoted relaxation into a meta-stable state. Second, the development of a saturated absorption spectrometer for detection of nitrous oxide. By saturating the P(18) ro-vibrational absorption line, a hole-burning feature can be created in the spectral line-shape. Measuring the broadening of this feature allows for Doppler-free pressure broadening coefficients to be measured. Third, the resonant infrared photodesorption of methane from a platinum single-crystal surface via resonant C-H stretch excitation. By tuning an optical parametric oscillator to the antisymmetric stretch mode of methane the rate of desorption was measured via change in Fourier transform infrared spectral intensity. A corresponding effective IR photodesorption cross-section, relevant to protostar ice mantle astrochemistry, was determined.

PHD (Doctor of Philosophy)

English

2023-11-29