PNNL

Abstract

The ?3 parallel, and ?6 perpendicular infrared-active vibrational bands have been analyzed for both CD379Br and CD381Br at 0.0015 cm-1 resolution. The band origins for the ?3 state are 577.28925(2) cm-1 and 575.97685(2) cm-1 for the CD379Br and CD381Br isotopologues, respectively; for the ?6 state the band origins are 713.46998(1) cm-1 and 713.38156(1) cm-1, respectively. The spectroscopic constants for both vibrational states, as well as the ground vibrational state were improved compared to previous studies, facilitated by the assignment of 5159 transitions for CD379Br, and 5219 transitions for CD381Br. The ?3 and ?6 vibrational states are expected to be the only unperturbed vibrational states in CD3Br, and thus yield the most reliable infrared spectroscopy-based determination of the ground state rotational constants. Ab initio calculations were performed to compare the efficacy of high-level theoretical calculations to accurately predict spectroscopic constants. Though not used in fitting the experimental data, nuclear quadrupole hyperfine splitting by the bromine atoms was observed in both vibrational states, an uncommon observation in the infrared spectra of polyatomic molecules. This work is not associated with any specific project, but Tony Masiello and John Vant were here during the summer of 2018. This work was supported in part by the U.S. Department of Energy, Office of Science, Office of Workforce Development for Teachers and Scientists (WDTS) under the Visiting Faculty Program (VFP).