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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Electronic States and Nonradiative Decay of Cold Gas-Phase Cinnamic Acid Derivatives Studied by Laser Spectroscopy with a Laser-Ablation Technique
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Electronic States and Nonradiative Decay of Cold Gas-Phase Cinnamic Acid Derivatives Studied by Laser Spectroscopy with a Laser-Ablation Technique

机译：激光烧蚀技术通过激光光谱研究的电子状态和非衰变的冷气相肉桂酸衍生物

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摘要

We performed UV spectroscopy for p-coumaric acid (pCA), ferulic acid (FA), and caffeic acid (CafA) under jet-cooled gas-phase conditions by using a laser-ablation source. These molecules showed the S-1((1)pi pi*)-S-0 absorption in the 31 500-33 500 cm(-1) region. Both pCA and FA exhibited sharp vibronic bands, while CafA showed only a broad feature. The decay time profile of the (1)pi pi* state was measured by picosecond pump-probe spectroscopy, and the transient state produced through the nonradiative decay (NRD) from (1)pi pi* and its time profile were measured by nanosecond UV-deep UV pump-probe spectroscopy. The transient state was observed for pCA and FA and assigned to the T-1 state, and we concluded that the NRD process of (1)pi pi* is S-1((1)pi pi*). (1)n pi* -> T-1((3)pi pi*), similar to those of methyl cinnamate and para-substituted cinnamates such as p-hydroxy and p-methoxy methyl cinnamate. On the other hand, the transient T-1 state was not detected in CafA, and its NRD route is suggested to be S-1((1)pi pi*). (1)pi sigma* -> H atom elimination, similar to those of phenol and catechol. The effect of a hydrogen bond on the electronic state and NRD process was investigated, and it was found that the H-bonding lowers the (1)pi pi* energy and suppresses the NRD process for all the species.
机译：通过使用激光烧蚀源在喷射冷却的气相条件下对P-香豆酸（PCA），阿魏酸（FA）和咖啡酸（CAFA）进行紫外光谱检查。这些分子显示S-1（（1）pi pi *） - S-0吸收在31 500-3300cm（-1）区域。 PCA和FA都表现出锋利的颤音频段，而CAFA只表现出广泛的功能。通过PICOSECOND泵探针光谱法测量（1）PI PI *状态的衰减时间分布，并通过纳秒UV测量通过（1）PI PI *的非衰减（NRD）和其时间谱产生的瞬态状态-deep uv泵探针光谱。观察到PCA和FA并分配给T-1状态的瞬态状态，我们得出结论，（1）PI PI *的NRD方法是S-1（（1）PI PI *）。 （1）N PI * - > T-1（（3）PI PI *），类似于肉桂酸甲酯和对甲基甲氧基甲基甲基甲基甲酸的甲基甲酸甲基甲酸甲基溴酸酯。另一方面，在CAFA中未检测到瞬时T-1状态，并且其NRD途径建议是S-1（（1）PI PI *）。 （1）pi sigma * - > H原子消除，类似于苯酚和儿茶酚的含量。研究了氢键对电子状态和NRD工艺的影响，发现H键合降低（1）PI PI *能量并抑制所有物种的NRD工艺。

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