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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >From the (1B) Spectroscopic State to the Photochemical Product of the Ultrafast Ring-Opening of 1,3-Cyclohexadiene: A Spectral Observation of the Complete Reaction Path
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From the (1B) Spectroscopic State to the Photochemical Product of the Ultrafast Ring-Opening of 1,3-Cyclohexadiene: A Spectral Observation of the Complete Reaction Path

机译：从（1B）光谱态到1,3-环己二烯超快开环的光化学产物：完整反应路径的光谱观察

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摘要

All stages of the electrocyclic ring-opening of 1,3-cyclohexadiene (CHD) were observed by time-resolved photoionization-photoelectron spectroscopy. Spectra of the 1B state, previously unobserved using time-resolved methods, were obtained upon optical excitation using ultrashort laser pulses at 4.60 or 4.65 eV, followed by ionization with pulses at 3.81, 3.85, and 4.10 eV, revealing a 1B lifetime of 30 fs. In an experiment using 3.07 eV probe photons and a 4.69 eV pump, we observed a time-sequenced progression of Rydberg states that includes s, p, and d states of the series n = 3 to 6. The sequentiality of the Rydberg signals points to an ionization mechanism that captures the molecule on different points along the reaction path in 2A. A dynamic fit of the Rydberg signals, coupled with MS-CASPT2 calculations, reveals that as the wavepacket moves down the potential energy surface it acquires kinetic energy at a rate of 28 eV/ps before reaching the conical intersection to the 1A ground state. During the reaction, the terminal carbon atoms separate at a speed of 16 angstrom/ps. A deconvolution of the Rydberg signals from a broad feature assigned to structurally disperse 1,3,5-hexatriene (HT) shows the formation of the open-chain hexatriene structure with an onset 142 fs after the initial absorption of a pump photon. The experimental observations are discussed in the context of recent ultrafast X-ray scattering experiments and theoretical quantum dynamics simulations.
机译：通过时间分辨光电离-光电子能谱观察了1，3-环己二烯（CHD）的电环开环的所有阶段。通过使用4.60或4.65 eV的超短激光脉冲进行光激发，然后以3.81、3.85和4.10 eV的脉冲进行电离，获得了1B状态的光谱，该光谱以前是用时间分辨方法观察不到的，显示了1 f的寿命为30 fs 。在使用3.07 eV探针光子和4.69 eV泵的实验中，我们观察到Rydberg状态的时间顺序变化，包括n = 3到6序列的s，p和d状态。Rydberg信号的顺序指向一种电离机制，可在2A中沿反应路径的不同点捕获分子。对Rydberg信号的动态拟合，再加上MS-CASPT2计算，揭示了当波包沿势能面向下移动时，它以28 eV / ps的速率获取动能，然后到达圆锥形相交点达到1A基态。在反应过程中，末端碳原子以16埃/秒的速度分离。从分配给结构上分散的1,3,5-己三烯（HT）的广泛特征对Rydberg信号进行去卷积显示，在泵浦光子的初始吸收之后，开链的hexatriene结构形成了142fs。在最近的超快X射线散射实验和理论量子动力学模拟的背景下讨论了实验观察结果。

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