Femtosecond real-time probing of the excited-state intramolecular proton transfer reaction in methyl salicylate
Femtosecond real-time probing of the excited-state intramolecular proton transfer reaction in methyl salicylate
复制标题
飞秒实时探测水杨酸甲酯中激发态分子内质子转移反应
DOI：
10.1063/1.5115307
复制
发表时间：
2019-09-07
影响因子：
4.4
通讯作者：
Wang, Pengfei
中科院分区：
文献类型：
--
作者：
Ling, Fengzi;Liu, Dejun;Wang, Pengfei
利用飞秒时间分辨离子产率光谱结合时间分辨光电子成像技术，研究了水杨酸甲酯中的激发态分子内质子转移（ESIPT）过程以及随后的电子弛豫动力学。用可调谐的泵浦脉冲激发，使酮式异构体处于第一激发电子态S₁(ππ*)。在100飞秒内，随着一个氢原子从酚羟基转移到羰基，分子几何结构逐渐改变，导致光电子电离通道发生变化。由于与一些中间里德堡态的偶然共振，随时间变化的光电子能谱直接描绘了从最初生成的酮式异构体到质子转移后的烯醇式异构体的ESIPT反应。随后，烯醇构型周围的布居在亚皮秒时间尺度上发生分子内振动再分布，接着以皮秒范围内与波长相关的寿命发生内转换回到基态。此外，还通过实验确定了水杨酸甲酯中几个里德堡态的激发能。
The excited-state intramolecular proton transfer (ESIPT) process and subsequent electronic relaxation dynamics in methyl salicylate have been investigated using femtosecond time-resolved ion yield spectroscopy combined with time-resolved photoelectron imaging. Excitation with a tunable pump pulse populates the keto tautomer in the first excited electronic state S-1(pi pi(*)). As a hydrogen atom transfers from the phenolic group to the carbonyl group within 100 fs, the molecular geometry changes gradually, leading to a variation in the electronic photoionization channel. By virtue of the accidental resonance with some intermediate Rydberg states, the time-dependent photoelectron spectra provide a direct mapping of the ESIPT reaction from the initially populated keto tautomer to the proton-transferred enol tautomer. Subsequently, the population around the enol configuration undergoes intramolecular vibrational redistribution on a subpicosecond time scale, followed by internal conversion to the ground state with a wavelength-dependent lifetime in the picosecond range. Furthermore, the excitation energies of several Rydberg states in methyl salicylate are determined experimentally.