Quartic Force Fields for Electronically Excited States of Interstellar Molecules

<p>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.</p>

Name thesis:degree_name

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

Level thesis:degree_level

Thesis (restricted to Georgia Southern)

Discipline thesis:degree_discipline

Department of Chemistry

Year dc:date.available

2015

Authors dc:creator

• Morgan, Whitney J
• Fortenberry, Ryan C

Contributors dc:contributor

• Sarah Higdon
• James LoBue

• ETD
• astrochemistry
• coupled cluster
• dipole bound
• excited state
• quartic force field
• rovibrational spectroscopy
• Atomic, Molecular and Optical Physics
• Physical Chemistry
• Stars, Interstellar Medium and the Galaxy

Repository record dc:identifier

https://digitalcommons.georgiasouthern.edu/etd/1251

OAI identifier oai:identifier

oai:digitalcommons.georgiasouthern.edu:etd-2354