PNNL

Abstract

The infrared spectrum of CD379Br and CD381Br between 900 cm-1 and 1400 cm-1 has been analyzed at high resolution. In this region, two fundamental vibrational states, v2 = 1 and v5 = 1, an overtone state, v3 = 2, and a combination state, v3 = v6 = 1, have been analyzed for both isotopologues. As found in other halomethane molecules, strong Coriolis resonances couple the v2 = 1 state to the v5 = 1 state, and similar resonances were also used to describe the coupling found between the v5 = 1 state to the v3 = 2 state. A new determination of the K-dependent constant A0 was performed for each isotopologue through the use of perturbation-allowed transitions. The values for A0 determined from the analysis are 2.6001898(26) and 2.6001905(27) for CD379Br and CD381Br, respectively. Ab initio calculations were performed to examine the efficacy of high-level theoretical calculations to accurately predict spectroscopic constants. The ab initio calculations had variable success with the largest errors associated with the prediction of the ?B rotational constants of the interacting states