Department of Chemistry, University of Durham, Durham DH1 3LE, U.K.
School of Chemistry, University of Melbourne, Parkville, Melbourne, Victoria 3010, Australia.
Sci Adv. 2017 May 19;3(5):e1603106. doi: 10.1126/sciadv.1603106. eCollection 2017 May.
Nonvalence states of molecular anions play key roles in processes, such as electron mobility, in rare-gas liquids, radiation-induced damage to DNA, and the formation of anions in the interstellar medium. Recently, a class of nonvalence bound anion state has been predicted by theory in which correlation forces are predominantly responsible for binding the excess electron. We present a direct spectroscopic observation of this nonvalence correlation-bound state (CBS) in the -toluquinone trimer cluster anion. Time-resolved photoelectron velocity map imaging shows that photodetachment of the CBS produces a narrow and highly anisotropic photoelectron distribution, consistent with detachment from an s-like orbital. The CBS is bound by ~50 meV and decays by vibration-mediated autodetachment with a lifetime of 700 ± 100 fs. These states are likely to be common in large and/or polarizable anions and clusters and may act as doorway states in electron attachment processes.
分子阴离子的非键合态在电子迁移率、稀有气体液体中的辐射损伤、星际介质中阴离子的形成等过程中起着关键作用。最近，理论预测了一类主要由关联力结合多余电子的非键合束缚阴离子态。我们在 - 对甲苯醌三聚体阴离子中直接观察到了这种非键合关联束缚态（CBS）。时间分辨光电子速度映射成像表明，CBS 的光离解产生了一个狭窄且各向异性的光电子分布，与从 s 轨道离解一致。CBS 结合能约为 50 meV，并通过振动介导的自离解衰减，寿命为 700 ± 100 fs。这些态很可能在大的和/或极化的阴离子和团簇中很常见，并且可能在电子俘获过程中充当 doorway 态。
