Presentation Title

Rovibronic Transitions of the Ethynyl Radical and Acetylide Anion: Quartic Force Field Methods for Spectroscopic Reference Data

Location

Room 2904 B

Session Format

Paper Presentation

Research Area Topic:

Natural & Physical Sciences - Chemistry

Co-Presenters, Co- Authors, Co-Researchers, Mentors, or Faculty Advisors

Dr. Ryan C. Fortenberry, co-author

Abstract

The reactive flexibility of carbon and the unique physics of the interstellar medium (ISM) allow for the formation of dozens of terrestrially unstable species with rich and often dense spectra. Laboratory characterization of these molecules has led to the assignment of many lines with simulated line lists supplementing this data in conjunction with databases such as HITRAN. However, the majority of this research has focused on the electronic ground state and vibrationally excited state assignments with little regard to the contributions of electronically excited states. Our group has recently demonstrated the utility of an ab initio quartic force field (QFF) approach to predict the spectroscopic qualities of several small organic radicals and their associated anions. Equation-of-motion (EOM) coupled cluster (CC) methods allow for the formal description of electronically excited states while QFFs provide the highly accurate determination of anharmonic ro-vibrational reference data. Rotational constants, anharmonic vibrational frequencies, and zero-point geometries serve to complete the picture for difficult spectral assignments. Several test cases of this powerful combination are provided with the isoformyl (HOC) radical, a moiety seen in countless carbon-rich systems, serving as the initial benchmark against traditional CCSD(T) results. Low-lying excited states such as those from the first 2Π state of the ethynyl (CCH) radical and potential dipole-bound excited states of the HOCO system are some of the challenges treated with this robust methodology.

Keywords

Spectroscopic, Rovibronic, Electronic excitation, EOM-CCSD, Quartic force field, QFF, Astrochemistry

Presentation Type and Release Option

Presentation (Open Access)

Start Date

4-24-2015 1:30 PM

End Date

4-24-2015 2:30 PM

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Apr 24th, 1:30 PM Apr 24th, 2:30 PM

Rovibronic Transitions of the Ethynyl Radical and Acetylide Anion: Quartic Force Field Methods for Spectroscopic Reference Data

Room 2904 B

The reactive flexibility of carbon and the unique physics of the interstellar medium (ISM) allow for the formation of dozens of terrestrially unstable species with rich and often dense spectra. Laboratory characterization of these molecules has led to the assignment of many lines with simulated line lists supplementing this data in conjunction with databases such as HITRAN. However, the majority of this research has focused on the electronic ground state and vibrationally excited state assignments with little regard to the contributions of electronically excited states. Our group has recently demonstrated the utility of an ab initio quartic force field (QFF) approach to predict the spectroscopic qualities of several small organic radicals and their associated anions. Equation-of-motion (EOM) coupled cluster (CC) methods allow for the formal description of electronically excited states while QFFs provide the highly accurate determination of anharmonic ro-vibrational reference data. Rotational constants, anharmonic vibrational frequencies, and zero-point geometries serve to complete the picture for difficult spectral assignments. Several test cases of this powerful combination are provided with the isoformyl (HOC) radical, a moiety seen in countless carbon-rich systems, serving as the initial benchmark against traditional CCSD(T) results. Low-lying excited states such as those from the first 2Π state of the ethynyl (CCH) radical and potential dipole-bound excited states of the HOCO system are some of the challenges treated with this robust methodology.