Al-Mogren Muneerah Mogren, Senent María Luisa
Chemistry Department, Faculty of Science, King Saud University, Riyadh, Saudi Arabia.
Departamento de Química y Física Teóricas, Instituto de Estructura de La Materia, IEM-CSIC, Madrid, Spain.
Front Chem. 2021 Sep 23;9:751203. doi: 10.3389/fchem.2021.751203. eCollection 2021.
CCSD(T)-F12 theory is applied to determine electronic ground state spectroscopic parameters of various isotopologues of methylamine (CH-NH) containing cosmological abundant elements, such as D, C and N. Special attention is given to the far infrared region. The studied isotopologues can be classified in the G, G and G molecular symmetry groups. The rotational and centrifugal distortion constants and the anharmonic fundamentals are determined using second order perturbation theory. Fermi displacements of the vibrational bands are predicted. The low vibrational energy levels corresponding to the large amplitude motions are determine variationally using a flexible three-dimensional model depending on the NH bending and wagging and the CH torsional coordinates. The model has been defined assuming that, in the amine group, the bending and the wagging modes interact strongly. The vibrational levels split into six components corresponding to the six minima of the potential energy surface. The accuracy of the kinetic energy parameters has an important effect on the energies. Strong interactions among the large amplitude motions are observed. Isotopic effects are relevant for the deuterated species.
耦合簇单双激发-完全活性空间自洽场微扰理论（CCSD(T)-F12）被用于确定含有宇宙中丰富元素（如氘、碳和氮）的甲胺（CH₃NH₂）各种同位素变体的电子基态光谱参数。特别关注远红外区域。所研究的同位素变体可归类于G、G'和G''分子对称群。利用二阶微扰理论确定转动常数和离心畸变常数以及非谐基本振动频率。预测了振动带的费米位移。对应于大幅度运动的低振动能级使用一个灵活的三维模型变分确定，该模型依赖于NH弯曲和摇摆以及CH扭转坐标。该模型的定义假设在胺基中，弯曲和摇摆模式强烈相互作用。振动能级分裂为对应于势能面六个极小值的六个分量。动能参数的精度对能量有重要影响。观察到大幅度运动之间有强相互作用。同位素效应与含氘物种相关。
