Date of Thesis

Fall 2021

Description

Modern laboratory measurements of the rate coefficients for the vibrational relaxation of CO(v=1) and CO(v=2) through collisions with CO have been accomplished. This work was motivated by the need for a robust non-LTE model to describe Titan’s upper atmosphere. Despite the importance of accurate rate measurements, the uncertainties associated with several CO quenching rate parameters in the literature are large. The experimental approach involved creating a temperature-jump in an equilibrium mixture of CO and bath gases by photolyzing a trace amount of O3 in the mixture with a pulsed UV laser. This shifted a small fraction of the CO population to excited vibrational states. Transient diode laser absorption spectroscopy was then used to observe the evolving vibrational state populations as a function of time. Rate coefficients were deduced from the change in collisional relaxation rate with quencher concentration. The rate coefficient for CO(v=2) self-quenching was measured to be (2.7 ± 0.6) x 10-12 cm3 molecule-1 s-1 and the overall rate coefficient for CO(v=1) self-quenching was measured to be (1.8 ± 0.3) x 10-12 cm3 molecule-1 s-1 . Each represents a significant decrease in uncertainty compared with values being used in current Titan non-LTE models.

Keywords

Physical Chemistry, Vibrational Relaxation, Kinetics, Diode Laser Spectroscopy, Pump/Probe Experiment

Access Type

Masters Thesis (Bucknell Access Only)

Degree Type

Master of Science

Major

Chemistry

First Advisor

Dr. Karen Castle

Second Advisor

Dr. Douglas Collins

Third Advisor

Dr. David Rovnyak

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