Jiang Jun, Ye Hong-Zhou, Nauta Klaas, Van Voorhis Troy, Schmidt Timothy W, Field Robert W
Center for Accelerator Mass Spectrometry, Lawrence Livermore National Laboratory, Livermore, California 94550, United States.
Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States.
J Phys Chem A. 2022 May 26;126(20):3090-3100. doi: 10.1021/acs.jpca.2c00495. Epub 2022 May 11.
Despite the long history of spectroscopic studies of the C molecule, fundamental questions about its chemical bonding are still being hotly debated. The complex electronic structure of C is a consequence of its dense manifold of near-degenerate, low-lying electronic states. A global multi-state diabatic model is proposed here to disentangle the numerous configuration interactions that occur within four symmetry manifolds of excited states of C (Π, Π, Σ , and Σ ). The key concept of our model is the existence of two "valence-hole" configurations, for Π states and for Σ states, that are derived from 3σ ← 2σ electron promotion. The lowest-energy state from each of the four C symmetry species is dominated by this type of valence-hole configuration at its equilibrium internuclear separation. As a result of their large binding energy (nominal bond order of 3) and correlation with the 2s2p + 2s2p separated-atom configurations, the presence of these valence-hole configurations has a profound impact on the global electronic structure and unimolecular dynamics of C.
尽管对C分子的光谱研究历史悠久，但关于其化学键的基本问题仍在激烈争论中。C的复杂电子结构是其近简并、低能级电子态的密集多重态的结果。本文提出了一个全局多态非绝热模型，以解开在C的激发态的四个对称多重态（Π、Π、Σ和Σ）内发生的众多组态相互作用。我们模型的关键概念是存在两种“价空穴”组态，对于Π态为 ，对于Σ态为 ，它们源自3σ←2σ电子跃迁。在平衡核间距下，四个C对称种类中每个的最低能量态都由这种价空穴组态主导。由于它们的大结合能（标称键级为3）以及与2s2p + 2s2p分离原子组态的相关性，这些价空穴组态的存在对C的全局电子结构和单分子动力学有深远影响。
