Department of Chemistry, Marquette University, P.O. Box 1881, Milwaukee, Wisconsin 53201, USA.
J Chem Phys. 2010 Nov 7;133(17):174310. doi: 10.1063/1.3495952.
We have carried out the first calculations of the infrared absorption spectrum of cyclic-N(3). Accurate vibrational energies and wave functions computed with incorporation of the geometric phase effect (via gauge theory) and using an ab initio potential energy surface were employed in this work. A sophisticated fully dimensional dipole moment function was constructed using accurate ab initio calculations and a three-dimensional-spline interpolation. Transformation of the dipole moment vector function from the reference frame associated with instantaneous principal axes of inertia to the laboratory-fixed reference frame was carried out using hyperspherical coordinates. We found that the permanent dipole moment of cyclic-N(3) in the ground vibrational state is relatively small (170 mD). The excited vibrational states show permanent dipole moments in the 10-25 mD range. The most intense part of the infrared absorption spectrum is observed in the deep infrared part of spectrum, 75-275 cm(-1), where five lines exhibit absolute absorption intensities in the range between 0.5 and 1.2 km/mol. These transitions correspond to excitation of the pseudorotational progression of states. Several unique spectroscopic features discussed in the paper should help to identify cyclic-N(3) in the laboratory.
我们已经对环状 N(3) 的红外吸收光谱进行了首次计算。在这项工作中，我们采用了包含几何相位效应（通过规范理论）和从头算势能面的精确振动能和波函数。使用精确的从头算计算和三维样条插值构建了复杂的全维偶极矩函数。通过超球坐标将偶极矩向量函数从与瞬时惯性主轴相关的参考系转换到实验室固定参考系。我们发现，基态下环状 N(3)的永久偶极矩相对较小（170 mD）。激发的振动状态在 10-25 mD 的范围内显示出永久偶极矩。红外吸收光谱中最强的部分出现在光谱的深红外部分，75-275 cm(-1)，其中五条线的绝对吸收强度在 0.5 到 1.2 km/mol 之间。这些跃迁对应于激发态的拟转子进动。本文讨论的几个独特的光谱特征应该有助于在实验室中识别环状 N(3)。
