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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Femtosecond UV Pump/Near-IR Probe Studies of the Solvent-Dependent Excited-State Decay Dynamics of Chlorine Dioxide
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Femtosecond UV Pump/Near-IR Probe Studies of the Solvent-Dependent Excited-State Decay Dynamics of Chlorine Dioxide

机译：飞秒紫外泵/近红外探针研究二氧化氯的溶剂依赖性激发态衰减动力学

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The excited-state decay and geminate-recombination dynamics of chlorine dioxide (OClO) are investigated using UV pumpear-IR probe spectroscpy. Experiments are performed with 200-fs time resolution on OClO dissolved in water, cyclohexane, acetonitrile, and chloroform. In all solvents, a reduction in optical density is observed at early times and is attributed to stimulated emission from the optically prepared ~2A_2 surface. The emission decays on the subpicosecond time scale to reveal an increase in optical density corresponding to the production of vibrationally hot ground-state OClO formed by geminate recombination of the primary photoproducts. Kinetic analysis of theses data reveals that the excited-state decay time constant increases from approx 200 fs in water and cyclohexane to approx 400 fs in acetonitrile and chloroform. The vibrational-relaxation dynamics of OClO are also found to be solvent dependent in agreement with earlier work. Pump-probe anisotropy experiments of aqueous OClO are presented. In these studies, an initial anisotropy of 0.40 +- 0.05 is observed consistent with emission from the optically prespared ~2A_2 state. However, the optical-density evolution for vibrationally hot OClO displays an anisotropy of 0.08+-0.03 suggesting that the mechanism of geminate recombination results in the retention of memory regarding the photoexcitation event. Potential recombination mechanisms consistent with this result are discussed.
机译：使用紫外泵浦/近红外探针光谱研究了二氧化氯（OClO）的激发态衰变和双峰重组动力学。对溶于水，环己烷，乙腈和氯仿的OClO进行了200 fs时间分辨率的实验。在所有溶剂中，早期都观察到光密度降低，这归因于从光学制备的〜2A_2表面发射的光。该发射在亚皮秒级的时间尺度上衰减，以揭示出光密度的增加，这与通过初级光产物的重整形成的振动热基态OClO的产生相对应。这些数据的动力学分析表明，激发态衰减时间常数从水和环己烷中的约200 fs增加到乙腈和氯仿中的约400 fs。还发现，OClO的振动松弛动力学与溶剂有关，这与早期的工作一致。提出了OClO水溶液的泵浦探针各向异性实验。在这些研究中，观察到的初始各向异性为0.40±0.05，与光学制备的〜2A_2状态的发射相一致。但是，振动热的OClO的光密度演化显示出0.08 + -0.03的各向异性，这表明，成对的重组机制导致保留了有关光激发事件的记忆。讨论了与此结果一致的潜在重组机制。

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