Term of Award

Spring 2015

Degree Name

Master of Science in Applied Physical Science (M.S.)

Document Type and Release Option

Thesis (restricted to Georgia Southern)

Copyright Statement / License for Reuse

Creative Commons License
This work is licensed under a Creative Commons Attribution 4.0 License.

Department

Department of Chemistry

Committee Chair

Ryan Fortenberry

Committee Member 1

Sarah Higdon

Committee Member 2

James LoBue

Abstract

Theoretical chemistry has advanced to the point where spectroscopic data can be produced that is directly comparable to high-accuracy experimental results. Quartic force field (QFFs) methods are one of the most efficient means of generating this data and have even shown spectroscopic accuracy (±1 cm−1) for fundamental vibrational frequencies. A method for extending QFFs to variationally inaccessible electronically excited states is presented herein using equation-of-motion (EOM) coupled cluster theory. The new EOM-based QFF is tested against the traditional QFF method using the isoformyl (HOC) radical’s variationally accessible 1 A” excited state and compared to previous benchmark studies. Challenges presented in this study are addressed in a second paper exploring the ethynyl (C2H) radical’s ground X 2Σ+ state and low-lying A 2Π state as well as its anionic form, the acetylide anion (C2H−). Special basis sets designed to treat diffuse (dipole-bound) states are developed in the final chapter which lays the foundation for the treatment of larger systems, such as anions, that posses dipole-bound excited states.

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