Department of Physics and Astronomy, Stony Brook University, Stony Brook, New York 11794, USA.
Department of Chemistry, Temple University, Philadelphia, Pennsylvania 19122, USA.
J Chem Phys. 2023 Apr 14;158(14):144303. doi: 10.1063/5.0146399.
Time-resolved photoionization measurements were performed on o-nitrophenol pumped with UV laser pulses at a central wavelength of 255 nm (4.9 eV) and probed with vacuum ultraviolet (VUV) pulses at 153 nm (8.1 eV). The photoelectron spectrum and time of flight mass spectrum for ions were recorded at each pump-probe delay. The measurements are interpreted with the aid of electronic structure calculations for both the neutral and ionic states. Evidence is found for the formation of a bicyclic intermediate followed by NO dissociation through a process of internal conversion and intersystem crossing. The combination of photoelectron and photoion spectroscopy, together with computational results, provides strong evidence of intersystem crossing that is difficult to establish with only a single technique.
时间分辨光致电离测量是在 255nm（4.9eV）的紫外激光脉冲泵浦下对邻硝基苯酚进行的，并在 153nm（8.1eV）的真空紫外（VUV）脉冲下进行探测。在每个泵浦-探测延迟时间，记录了离子的光电子能谱和飞行时间质谱。测量结果借助于中性和离子态的电子结构计算进行解释。发现形成双环中间体，然后通过内部转换和系间窜越过程通过 NO 解离。光电子和光致离子光谱的结合以及计算结果提供了系间窜越的有力证据，而仅使用单一技术很难确定系间窜越。
