Wei Jie, Cao Ling, Song Xinli, Wang Yanmei, Zhang Song, Zhang Bing
State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Innovation Academy for Precision Measurement Science and Technology, Chinese Academy of Sciences, Wuhan 430071, People's Republic of China.
J Chem Phys. 2022 Nov 28;157(20):204302. doi: 10.1063/5.0128567.
Coherent nuclear wavepacket behavior obtained by time-resolved spectroscopy is a good choice to capture the real-time evolution of molecular configuration. Using femtosecond time-resolved photoelectron imaging, we investigate the real-time evolution of the vibrational wavepacket of 2,5-difluoroaniline following the coherent excitation of an out-of-plane vibrational mode in the S state at 289.8 nm. Probed by an accidental resonance with the Rydberg states, the periodic oscillations with the frequency of 99 cm are observed from the photoelectron kinetic energy (PKE) distributions, corresponding to the energy difference between the out-of-plane mode X of C-F bond and the band origin. Moreover, phase reversal of π rad between 0.66-0.75 and 1.00-1.08 eV is also observed in the PKE region. Combined with the scan of the potential energy surface in the ground cationic D state, the observed two ionization channels corresponding to different phases are attributed to the periodic geometry changes between the planar and the non-planar structures when the coherent wavepacket evolves from the initial vertical Franck-Condon region toward the global minimum of the S potential energy surface.
通过时间分辨光谱获得的相干核波包行为是捕捉分子构型实时演化的良好选择。利用飞秒时间分辨光电子成像技术，我们研究了在289.8 nm激发S态面外振动模式后，2,5-二氟苯胺振动波包的实时演化。通过与里德堡态的偶然共振进行探测，从光电子动能（PKE）分布中观察到频率为99 cm的周期性振荡，这对应于C-F键的面外模式X与能带起源之间的能量差。此外，在PKE区域还观察到0.66 - 0.75 eV和1.00 - 1.08 eV之间π rad的相位反转。结合基态阳离子D态势能面的扫描，观察到的对应于不同相位的两个电离通道归因于相干波包从初始垂直弗兰克 - 康登区域向S势能面全局最小值演化时，平面和非平面结构之间的周期性几何变化。
