Accurate rate coefficients of atomic and molecular processes allow us to probe the conditions in space and understand the history of the Universe. Although experimental rate coefficients are the most desirable, availability of accurate rate coefficients of some processes depends on rigorous theoretical studies. In this dissertation, theoretical tools for collisions involving three bodies are discussed and applied to three different reactions. Rate coefficient of the reactive scattering of H2 + D- is computed using the ABC program. The present results are about ten times smaller than the experimental upper limit, suggesting that a further improvement of the sensitivity of the signal in the experiment may lead to the observation of the H- ions produced from this reaction. For the isotopic exchange reaction of 16O16O + 18O, the multiconfiguration time-dependent Hartree method was used to model the time evolution of the reaction. The results suggest that distribution of final reaction products is highly anisotropic, and simplified statistical approaches, sometime used for this kind of processes, are not applicable to this reaction. The three-body recombination of hydrogen atoms is investigated using the hyperspherical adiabatic approach with the R-matrix method at zero total angular momentum. It is found that Jahn-Teller effect contributes less than 15% increase in the total three-body recombination rate. The nascent population of the H2 molecules, formed in the recombination process, is found to be dominated by highly excited rovibrational levels, which could have substantial impacts in some astrophysical models. In addition, a novel simplified approach for dissociative electron attachment to polyatomic molecules is developed and applied to H2CN. The estimated rate coefficient is found to be too small to contribute to formation of CN- in the interstellar medium. An accurate theoretical rate coefficient of dissociative recombination of prebiotic molecule CH2NH2+ is also reported. The reported value is consistent with databases for astrochemistry, but it is much smaller than the value used in photochemical models of the upper atmosphere of Titan, which has an impact on Titan ammonia abundance in the models.
Doctor of Philosophy (Ph.D.)
College of Sciences
Length of Campus-only Access
Doctoral Dissertation (Open Access)
Yuen, Chi Hong, "Theoretical Studies of Collisions Involving Three Bodies and Electron-Molecule Collisions Relevant to Astrophysical and Atmospheric Conditions" (2020). Electronic Theses and Dissertations, 2020-. 317.