Abstract The rovibrational spectrum of the NO(X2Π)–CO2 open-shell complex has been measured in the fundamental band region of NO using an infrared laser absorption spectrometer. Geometry optimizations at restricted configurations with a Cs symmetry at the RCCSD(T)/aug-cc-pvtz level of theory predict that this complex has a T-shaped structure at the global minimum on the ground electronic state (2A”), with the N atom of NO pointing to the C atom of CO2. The observed spectrum is analyzed with an effective Hamiltonian for a planar T-shaped open-shell complex. Half of the possible rotational levels are missing due to spin statistics of the two identical 16O nuclei (I = 0) in the CO2 subunit of the complex. The band-origin of the complex is located at 1880.4518(67) cm-1, which is blue-shifted from that of the NO monomer by about 4.48 cm-1. The rotational constants and the quenching parameter of the electronic orbital angular momentum of NO in both ground and excited vibrational states have been determined accurately. The intermolecular distance between centers of mass of CO2 and NO in the ground state is determined to be R = 3.703 A.

中文翻译：

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NO(X2Π)-CO2 开壳配合物的振动光谱和结构

摘要 使用红外激光吸收光谱仪在 NO 基带区测量了 NO(X2Π)-CO2 开壳复合物的振动光谱。在 RCCSD(T)/aug-cc-pvtz 理论水平上具有 Cs 对称性的受限配置的几何优化预测，该复合体在基电子态 (2A") 的全局最小值处具有 T 形结构，其中NO 的 N 原子指向 CO2 的 C 原子。观察到的光谱是用一个有效的哈密顿量来分析的，用于平面 T 形开壳复合体。由于复合体的 CO2 亚基中两个相同的 16O 原子核 (I = 0) 的自旋统计数据丢失了一半的可能旋转水平。该复合物的带原点位于 1880.4518(67) cm-1，与 NO 单体的带原点蓝移约 4.48 cm-1。NO在基态和激发态的电子轨道角动量的旋转常数和猝灭参数已被准确确定。基态中 CO2 和 NO 的质心之间的分子间距离确定为 R = 3.703 A。