Nunes J P F, Williams M, Yang J, Wolf T J A, Rankine C D, Parrish R, Moore B, Wilkin K, Shen X, Lin Ming-Fu, Hegazy K, Li R, Weathersby S, Martinez T J, Wang X J, Centurion M
Department of Physics and Astronomy, University of Nebraska-Lincoln, Lincoln, USA.
SLAC National Accelerator Laboratory, Menlo Park, USA.
Phys Chem Chem Phys. 2024 Jul 3;26(26):17991-17998. doi: 10.1039/d3cp06253h.
The photo-induced dynamics of -nitrophenol, particularly its photolysis, has garnered significant scientific interest as a potential source of nitrous acid in the atmosphere. Although the photolysis products and preceding photo-induced electronic structure dynamics have been investigated extensively, the nuclear dynamics accompanying the non-radiative relaxation of -nitrophenol on the ultrafast timescale, which include an intramolecular proton transfer step, have not been experimentally resolved. Herein, we present a direct observation of the ultrafast nuclear motions mediating photo-relaxation using ultrafast electron diffraction. This work spatiotemporally resolves the loss of planarity which enables access to a conical intersection between the first excited state and the ground state after the proton transfer step, on the femtosecond timescale and with sub-Angstrom resolution. Our observations, supported by multiple spawning simulations, provide new insights into the proton transfer mediated relaxation mechanism in -nitrophenol.
对硝基苯酚的光致动力学，尤其是其光解过程，作为大气中潜在的亚硝酸来源已引起了科学界的广泛关注。尽管光解产物及之前的光致电子结构动力学已得到广泛研究，但在超快时间尺度上伴随对硝基苯酚非辐射弛豫的核动力学，包括分子内质子转移步骤，尚未通过实验得到解决。在此，我们利用超快电子衍射直接观察了介导光弛豫的超快核运动。这项工作在飞秒时间尺度和亚埃分辨率下，从时空上解析了平面性的丧失，这使得我们能够在质子转移步骤之后进入第一激发态与基态之间的锥形交叉点。我们的观察结果得到了多次生成模拟的支持，为对硝基苯酚中质子转移介导的弛豫机制提供了新的见解。
