Abstract The high-resolution Fourier transform infrared spectrum of methyl bromide CH3Br has been reinvestigated in the v3 = 2 vibrational excited state around 1213 cm−1, for both 79Br and 81Br isotopologues. Thanks to new accurate K-dependent and J-dependent ground state parameters, up to sextic centrifugal distortion constants, 420 new infrared transitions of the 2ν3 rovibrational band have been assigned for CH379Br and CH381Br, extending the rotational quantum number values up to Kmax = 15 and Jmax = 60. For each isotopic species, a standard deviation of 2 × 10−4 cm−1 has been obtained for about 700 lines of 2ν3. The new parameter values of the v3 = 2 excited state are in good agreement with ones determined previously by infrared spectroscopy, but significantly more accurate.

中文翻译：

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1213 cm-1 附近甲基溴 CH3Br 2ν3 (A1) 红外波段的新处理

摘要 79Br 和 81Br 同位素体在 1213 cm-1 附近的 v3 = 2 振动激发态中重新研究了甲基溴 CH3Br 的高分辨率傅里叶变换红外光谱。由于新的准确的 K 相关和 J 相关基态参数，高达六次离心畸变常数，已为 CH379Br 和 CH381Br 分配了 2ν3 旋转带的 420 个新红外跃迁，将旋转量子数值扩展至 Kmax = 15并且 Jmax = 60。对于每个同位素物种，已经获得了大约 700 条 2ν3 谱线的 2 × 10−4 cm−1 标准偏差。v3 = 2 激发态的新参数值与先前通过红外光谱确定的参数值非常一致，但准确度更高。