Abstract The high-resolution Fourier transform infrared (FTIR) spectrum of the ν 12 band of formaldoxime (CH2NOH) was recorded at the Australian Synchrotron with an unapodized resolution of 0.0018 cm−1 in the 320–460 cm−1 region. A total of 1895 infrared transitions were fitted using the Watson's A-reduced Hamiltonian in the Ir representation with a root-mean-square (rms) deviation of 0.000156 cm−1. From this rovibrational analysis, the ν 12 = 1 state rotational constants (A and C) and five quartic terms (ΔJ, ΔJK, ΔK, δJ, δK) were improved from previous work and three sextic terms (ΦJK, ΦKJ, ΦK) were derived for the first time. The band center of the ν 12 band of CH2NOH was found to be 397.685235(23) cm−1. All five quartic centrifugal distortion terms of the ground state were also improved with higher accuracy. The ground state ΦJK, ΦKJ, ΦK were obtained for the first time through the fitting of 1501 ground state combination differences (GSCDs) derived from the IR transitions of the ν 12 and ν 10 bands, together with 23 previously reported microwave frequencies. The rms deviation of this GSCD fit was 0.000687 cm−1. Additionally, rotational constants and higher order centrifugal distortion terms of the ground and v 12 = 1 states were computed from theoretical anharmonic calculations at two different levels of theory, B3LYP and MP2 with the cc-pVTZ basis set, for comparison with the experimental results. The calculated and experimental rovibrational constants of CH2NOH for both ground and v 12 = 1 states were in good agreement.

中文翻译：

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改进的基态和 v12 = 1 状态的甲醛肟 (CH2NOH) 振动常数

摘要 在澳大利亚同步加速器上记录了甲醛肟 (CH2NOH) ν 12 带的高分辨率傅里叶变换红外 (FTIR) 光谱，在 320-460 cm-1 区域内的未变迹分辨率为 0.0018 cm-1。在 Ir 表示中使用 Watson 的 A 约简哈密顿量拟合了总共 1895 个红外跃迁，均方根 (rms) 偏差为 0.000156 cm-1。从该振动分析中，v 12 = 1 状态旋转常数（A 和 C）和五个四次项（ΔJ、ΔJK、ΔK、δJ、δK）从以前的工作中得到改进，三个六次项（ΦJK、ΦKJ、ΦK）是第一次得出。发现 CH2NOH 的 ν 12 带的带中心为 397.685235(23) cm-1。基态的所有五个四次离心畸变项也得到了更高的改进。基态ΦJK、ΦKJ、ΦK 是第一次通过拟合 1501 个基态组合差异 (GSCD) 获得的，这些差异源自 ν 12 和 ν 10 波段的 IR 跃迁，以及之前报道的 23 个微波频率。此 GSCD 拟合的均方根偏差为 0.000687 cm-1。此外，地面和 v 12 = 1 状态的旋转常数和高阶离心畸变项是根据两个不同理论水平的理论非谐计算计算的，B3LYP 和 MP2 与 cc-pVTZ 基组，用于与实验结果进行比较。计算的和实验的 CH2NOH 在地面和 v 12 = 1 状态下的振动常数非常一致。