Abstract The ν3 parallel, and ν6 perpendicular infrared-active vibrational bands have been analyzed for both CD379Br and CD381Br at 0.0015 cm-1 resolution. The band origins for the v3 = 1 state are 577.28925(2) cm-1 and 575.97685(2) cm-1 for the CD379Br and CD381Br isotopologues, respectively; for the v6 = 1 state the band origins are 713.46997(1) cm-1 and 713.38156(1) cm-1, respectively. The v3 =1 and v6 =1 vibrational states are possibly the only unperturbed vibrational states in CD3Br, and thus yield the most reliable infrared spectroscopy-based determination of the ground state rotational constants. The spectroscopic constants for both vibrational states, as well as the ground vibrational state were improved compared to previous studies through a direct fit of the vibrational bands, as well as a separate fit of the ground state combination differences. Ab initio calculations were performed to examine 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.

中文翻译：

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CD3Br ν3 和 ν6 波段的高分辨率红外分析

摘要 以 0.0015 cm-1 的分辨率分析了 CD379Br 和 CD381Br 的 ν3 平行和 ν6 垂直红外活性振动带。对于 CD379Br 和 CD381Br 同位素体，v3 = 1 状态的谱带起点分别为 577.28925(2) cm-1 和 575.97685(2) cm-1；对于 v6 = 1 状态，带原点分别为 713.46997(1) cm-1 和 713.38156(1) cm-1。v3 =1 和 v6 =1 振动态可能是 CD3Br 中唯一未受干扰的振动态，因此产生了最可靠的基于红外光谱的基态旋转常数测定。与之前的研究相比，通过直接拟合振动带，两种振动状态和地面振动状态的光谱常数都得到了改善，以及基态组合差异的单独拟合。进行了从头算计算以检查高级理论计算对准确预测光谱常数的功效。尽管未用于拟合实验数据，但在两种振动状态下均观察到溴原子引起的核四极超精细分裂，这是多原子分子红外光谱中不常见的观察结果。