We report our analysis of the pure rotational spectra of low-lying vibrationally excited states and heavy-atom rare isotopologues of imidazole. To facilitate searches for imidazole in the interstellar medium, we previously described the analysis of the rotational spectrum of the imidazole main isotopologue across the 2–295 GHz range, and we extend this analysis here. Structure optimisation and anharmonic frequency calculations were performed to aid the spectral analysis. Three vibrationally excited states of imidazole were assigned in our room-temperature spectra, with energies up to approximately 670 cm⁻¹ above the vibronic ground state. The vibrational states could act as temperature probes in warmer star-forming regions. The ¹³C and ¹⁵N heavy-atom isotopologues were assigned, which allowed for the structure of imidazole in the gas phase to be determined. Structural comparisons are drawn between the related heterocyclic molecules hydantoin and imidazolidine. An experimental gas-phase structure of the former is also determined in this work. The potential detection of the isotopologues could help deduce formation pathways towards imidazole and other nitrogen-containing cyclic compounds in interstellar space.

我们报告了对低位振动激发态和咪唑重原子稀有同位素的纯旋转光谱的分析。为了方便在星际介质中搜索咪唑，我们先前描述了在2–295 GHz范围内对咪唑主要同位素的旋转光谱的分析，在此将其扩展。进行了结构优化和非谐频率计算，以帮助进行频谱分析。在我们的室温光谱中，分配了咪唑的三个振动激发态，其能量比振动基态高出约670 cm ^-1。振动状态可以在较暖的恒星形成区域中充当温度探测器。的¹³ C和¹⁵分配了N个重原子同位素，可以确定气相中咪唑的结构。在相关的杂环分子乙内酰脲和咪唑烷之间进行结构比较。在这项工作中还确定了前者的实验气相结构。潜在的同位素同位素检测可以帮助推断星际空间中咪唑和其他含氮环状化合物的形成途径。