Date of Award
Spring 2017
Document Type
Dissertation
Degree Name
Doctor of Philosophy (PhD)
Department
Chemistry
First Advisor
Babikov, Dmitri
Second Advisor
Reid, Scott
Third Advisor
Huang, Jier
Abstract
The ozone forming recombination reaction stands out among many chemical processes that take place in the atmosphere. This reaction is responsible for the reconstruction of ozone layer, which protects life on Earth from harmful ultra-violate radiation and is a source of so-called anomalous isotope effect in ozone. The reaction was intensively studied, but at a very basic level. There were only couple of papers where the recombination rate coefficient was computed and found to roughly agree with the experimental data. In this dissertation, the recombination process in ozone is approached using new and efficient method, which includes several modern techniques. The rovibrational scattering resonances of O3 are characterized by solving three-dimensional time-independent Schrödinger equation in symmetric-top approximation. The widths (or lifetimes) of scattering resonances are computed using complex absorbing potential. The high efficiency is achieved by using convenient vibrational coordinates, optimal grid for dissociative coordinate and construction of small Hamiltonian matrix in locally optimal basis. The symmetry of the problem is also utilized by implementing a symmetry-adapted basis for one of vibrational coordinates. Stabilization of scattering resonances is described approximately, using mixed quantum/classical theory, for which an efficient frozen rotor approximation is developed. The rate coefficient of ozone recombination, predicted here for unsubstituted ozone, 48O3, as well as its pressure and temperature dependencies, agrees very well with experimental data. The isotope effects, one related to zero-point energy and another to symmetry, are studied for a limited number of rotational excitations and for two isotopologues 50O3 and 52O3 (singly and doubly substituted with 18O). Both effects were found to be in the right direction and of right order of magnitude. The width of scattering resonances control these isotope effects. The approach is universal and can be applied to any other similar system, for example, S3.