Rajak Karunamoy, Ghosh Arpita, Mahapatra S
School of Chemistry , University of Hyderabad , Hyderabad 500 046 , India.
J Phys Chem A. 2018 Nov 1;122(43):8612-8625. doi: 10.1021/acs.jpca.8b08171. Epub 2018 Oct 22.
We examine vibronic coupling in the first five electronic states (X̃Π-ÃΠ-B̃Σ-C̃Σ-D̃Π-ẼΠ) of dicyanodiacetylene radical cation (CN) in this article. Prompted by the prediction of its existence in the astrophysical environment, the vibronic band structure of these electronic states of CN has been probed in spectroscopic measurements in laboratory by various groups. Inspired by numerous experimental data, we undertook the task of investigating topographical details of electronic potential energy surfaces, their coupling mechanism and nuclear dynamics on them. The degenerate Π electronic states of this radical are prone to Renner-Teller instability, and in addition symmetry allowed Σ-Π and Π-Π vibronic coupling is expected to play crucial role in the detailed vibronic structure of each of the above electronic states. A vibronic coupling model is developed here and first-principles nuclear dynamics study is carried out employing quantum mechanical methods. The vibronic band structure thus calculated is compared with experimental results and the progressions are identified and assigned. The nonradiative internal conversion dynamics among electronic states is also examined and discussed in relation to the various coupling of electronic states.
在本文中，我们研究了二氰基乙炔自由基阳离子（CN）的前五个电子态（X̃Π-ÃΠ-B̃Σ-C̃Σ-D̃Π-ẼΠ）中的振动-电子耦合。受其在天体物理环境中存在的预测的启发，不同研究小组在实验室的光谱测量中对CN这些电子态的振动-电子能带结构进行了探测。受大量实验数据的启发，我们承担了研究电子势能面的地形细节、它们的耦合机制以及其上的核动力学的任务。该自由基的简并Π电子态易于发生Renner-Teller不稳定性，此外，对称性允许的Σ-Π和Π-Π振动-电子耦合预计在上述每个电子态的详细振动-电子结构中起关键作用。本文建立了一个振动-电子耦合模型，并采用量子力学方法进行了第一性原理核动力学研究。将由此计算得到的振动-电子能带结构与实验结果进行比较，并识别和归属跃迁。还研究并讨论了电子态之间的非辐射内转换动力学与电子态的各种耦合的关系。
