Röder Anja, Skov Anders B, Boguslavskiy Andrey E, Lausten Rune, Stolow Albert
Department of Chemistry, University of Ottawa, 150 Louis-Pasteur Pvt, Ottawa, Ontario K1N 6N5, Canada.
Phys Chem Chem Phys. 2020 Nov 25;22(45):26241-26254. doi: 10.1039/d0cp04292g.
The vacuum ultraviolet (VUV) absorption spectra of cyclic ethers consist primarily of Rydberg ← n transitions. By studying three cyclic ethers of varying ring size (tetrahydropyran, tetrahydrofuran and trimethylene oxide, n = 6-4), we investigated the influence of ring size on the VUV excited-state dynamics of the 3d Rydberg manifold using time-resolved photoelectron spectroscopy (TRPES), time-resolved mass spectroscopy (TRMS) and ab initio electronic structure calculations. Whereas neither the electronic characters nor the term energies of the excited-states are substantially modified when the ring-size is reduced from n = 6 to 5 to 4, the excited-state lifetimes concomitantly decrease five-fold. TRPES and TRMS allow us to attribute the observed dynamics to a Rydberg cascade from the initially excited d-Rydberg manifold via the p-Rydberg manifold to the s-Rydberg state. Cuts through potential energy surfaces along the C-O bond reveal that a nσ* state crossing brings the s-Rydberg state along a path to the ring-opened ground state. The observed difference in excited-state lifetimes is attributed to an increasing slope along the repulsive C-O bond coordinate as ring size decreases.
环状醚的真空紫外（VUV）吸收光谱主要由里德堡←n跃迁组成。通过研究三种不同环大小的环状醚（四氢吡喃、四氢呋喃和环氧丙烷，n = 6 - 4），我们使用时间分辨光电子能谱（TRPES）、时间分辨质谱（TRMS）和从头算电子结构计算，研究了环大小对3d里德堡多重态的VUV激发态动力学的影响。当环大小从n = 6减小到5再到4时，激发态的电子特征和能级都没有实质性改变，但激发态寿命相应地减少了五倍。TRPES和TRMS使我们能够将观察到的动力学归因于从最初激发的d - 里德堡多重态通过p - 里德堡多重态到s - 里德堡态的里德堡级联。沿着C - O键切割势能面表明，一个nσ*态交叉使s - 里德堡态沿着一条通向开环基态的路径。观察到的激发态寿命差异归因于随着环大小减小，沿着排斥性C - O键坐标的斜率增加。
