At low excitation energies of under 5 eV, conical intersections (CIs) involving the lowest three electronic states of aniline, viz. the ${}^1\pi {\pi }^{\ast }/{}^1\pi {\sigma }^{\ast }$ and ${}^1\pi {\sigma }^{\ast }$/GS intersections, are accessible. Signatures of ultrafast dynamics, including H atom loss, are observed experimentally with energies above the ${}^1\pi {\sigma }^{\ast }$ threshold. Ab initio results corroborate the view that the intersections are involved in the rapid population flow. In the present computational study, we characterize these intersections using the CASSCF and XMS-CASPT2 methods. We locate the CIs and analyse the important vibronic couplings at these geometries from a normal mode as well as an NH₂ local mode perspective. Through our findings, we suggest that modes largely local to the NH₂ group couple the electronic states the strongest at these intersections.

在低于5 eV的低激发能下，圆锥形交叉点（CIs）涉及苯胺的最低三个电子态，即。这${}^{\mathrm{1个}}\pi {\pi }^{\ast }/{}^{\mathrm{1个}}\pi {\sigma }^{\ast }$ 和 ${}^{\mathrm{1个}}\pi {\sigma }^{\ast }$/ GS交叉点，可访问。实验观察到的超快动力学的特征包括氢原子的损失。${}^{\mathrm{1个}}\pi {\sigma }^{\ast }$临界点。从头算结果证实了交叉口参与快速人口流动的观点。在当前的计算研究中，我们使用CASSCF和XMS-CASPT2方法来表征这些交点。我们找到CI并从正常模式以及NH ₂局部模式的角度分析这些几何形状的重要电声耦合。通过我们的发现，我们建议在很大程度上，NH ₂基团局部的模式将这些交点处最强的电子态耦合在一起。