Term of Award
Master of Science in Applied Physical Science (M.S.)
Document Type and Release Option
Thesis (restricted to Georgia Southern)
Copyright Statement / License for Reuse
This work is licensed under a Creative Commons Attribution 4.0 License.
Committee Member 1
Committee Member 2
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.
Morgan, Whitney J. and Fortenberry, Ryan C., "Quartic Force Fields for Electronically Excited States of Interstellar Molecules" (2015). Electronic Theses & Dissertations. 1251.