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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Deconstructing the excited-state dynamics of β-carotene in solution
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Deconstructing the excited-state dynamics of β-carotene in solution

机译：解构溶液中β-胡萝卜素的激发态动力学

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摘要

The femtosecond to nanosecond dynamics of the all-trans β-carotene carotenoid dissolved in 3-methylpentane is characterized and dissected with excitation-wavelength and temperature-dependent ultrafast dispersed transient absorption signals. The kinetics measured after red-edge (490 nm) and blue-edge (400 nm) excitation were contrasted under fluid solvent (298 K) and rigid glass (77 K) conditions. In all four measured data sets, the S* population kinetics was resolved prompting the development of a modified multicompartment model. The temperature-dependent and excitation wavelength-dependent S* quantum yield is ascribed to a competition of population surmounting a weak (55 cm~(- 1)) energy barrier on the S_2 state to favor S _1 generation and rapid internal conversion that favors S* generation. When cooled from room temperature to 77 K, the S* decay time scale shifted significantly from 30 to 400 ps, which is ascribed to small-scale structural relaxation with a 115 cm~(- 1) energy barrier. For the first time under low-energy excitation conditions, the triplet state is observed and confirmed to not originate from S* or S_1, but from S _2. The interconnectivity of the S* and S_1 populations is discussed, and no observed population flow is resolved between S* and S_1. Comparison of samples obtained from different laboratories with different purity levels demonstrates that sample contamination is not the primary origin of the S* state.
机译：溶解于3-甲基戊烷中的全反式β-胡萝卜素类胡萝卜素的飞秒至纳秒级动力学特性，并通过激发波长和温度相关的超快分散瞬态吸收信号进行了剖析。在流体溶剂（298 K）和刚性玻璃（77 K）条件下，对比了红边（490 nm）和蓝边（400 nm）激发后测得的动力学。在所有四个测量数据集中，解决了S *种群动力学问题，从而促进了改进的多室模型的发展。温度依赖和激发波长依赖的S *量子产率归因于在S_2态上克服弱的（55 cm〜（-1））能垒以促进S _1产生和促进S的快速内部转化的种群竞争*代。当从室温冷却到77 K时，S *衰减时间尺度从30 ps显着变化到400 ps，这归因于具有115 cm〜（-1）能垒的小尺度结构弛豫。在低能激发条件下，首次观察到三重态并确认其并非源自S *或S_1，而是源自S _2。讨论了S *和S_1种群的互连性，并且在S *和S_1之间没有解决观察到的种群流动。从不同实验室获得的纯度不同的样品的比较表明，样品污染不是S *状态的主要来源。

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