Markmann Verena, Pan Jaysree, Hansen Bianca L, Haubro Morten L, Nimmrich Amke, Lenzen Philipp, Levantino Matteo, Katayama Tetsuo, Adachi Shin-Ichi, Gorski-Bilke Simone, Temps Friedrich, Dohn Asmus O, Møller Klaus B, Nielsen Martin M, Haldrup Kristoffer
Technical University of Denmark Anker Engelunds Vej 1 2800 Lyngby Denmark
Department of Chemistry and Molecular Biology, University of Gothenburg Gothenburg Sweden.
Chem Sci. 2024 Jun 12;15(29):11391-11401. doi: 10.1039/d4sc01912a. eCollection 2024 Jul 24.
This work investigates and describes the structural dynamics taking place following charge-transfer-to-solvent photo-abstraction of electrons from I and Br ions in aqueous solution following single- and 2-photon excitation at 202 nm and 400 nm, respectively. A Time-Resolved X-ray Solution Scattering (TR-XSS) approach with direct sensitivity to the structure of the surrounding solvent as the water molecules adopt a new equilibrium configuration following the electron-abstraction process is utilized to investigate the structural dynamics of solvent shell expansion and restructuring in real-time. The structural sensitivity of the scattering data enables a quantitative evaluation of competing models for the interaction between the nascent neutral species and surrounding water molecules. Taking the I-O distance as the reaction coordinate, we find that the structural reorganization is delayed by 0.1 ps with respect to the photoexcitation and completes on a time scale of 0.5-1 ps. On longer time scales we determine from the evolution of the TR-XSS difference signal that I: e recombination takes place on two distinct time scales of ∼20 ps and 100 s of picoseconds. These dynamics are well captured by a simple model of diffusive evolution of the initial photo-abstracted electron population where the charge-transfer-to-solvent process gives rise to a broad distribution of electron ejection distances, a significant fraction of which are in the close vicinity of the nascent halogen atoms and recombine on short time scales.
本工作研究并描述了在202 nm和400 nm分别进行单光子和双光子激发后，水溶液中I⁻和Br⁻离子发生电荷转移至溶剂的光电子提取后所发生的结构动力学。采用时间分辨X射线溶液散射（TR-XSS）方法，该方法对周围溶剂的结构具有直接敏感性，因为在电子提取过程后水分子会采用新的平衡构型，以此实时研究溶剂壳层扩展和重组的结构动力学。散射数据的结构敏感性使得能够对新生中性物种与周围水分子之间相互作用的竞争模型进行定量评估。以I-O距离作为反应坐标，我们发现结构重组相对于光激发延迟了0.1 ps，并在0.5 - 1 ps的时间尺度上完成。在更长的时间尺度上，我们从TR-XSS差异信号的演化中确定，I⁻:e⁻复合发生在约20 ps和100多皮秒这两个不同的时间尺度上。这些动力学可以通过一个简单的初始光提取电子群体扩散演化模型很好地捕捉，其中电荷转移至溶剂的过程导致电子喷射距离的广泛分布，其中很大一部分在新生卤原子的紧邻区域，并在短时间尺度上复合。
