Effects of tunable excitation in carotenoids explained by the vibrational energy relaxation approach
Effects of tunable excitation in carotenoids explained by the vibrational energy relaxation approach
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DOI：
10.1007/s11120-017-0423-6
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发表时间：
2018-03-01
影响因子：
3.7
通讯作者：
Abramavicius, Darius
中科院分区：
文献类型：
--
作者：
Balevicius, Vytautas, Jr.;Lincoln, Craig N.;Abramavicius, Darius
类胡萝卜素是自然光收集器的基本构件，具有复杂的超快能量失活网络。为了解开这种复杂的弛豫动力学，一些研究集中在瞬时吸收测量及其与泵浦波长的关系上。然而，这样的发现并不确定，有时甚至自相矛盾。在这项研究中，我们比较了在第一、第二和第三振动级数峰值泵浦的胡萝卜素的内部转换动力学。我们采用完全量子力学模型来显式处理高频对称碳-碳(C=C和C-C)伸缩模式，而不是采用基于整体分析的数据拟合算法。这个模型成功地描述了观察到的布居动力学和谱线形状随时间的变化，并使我们得到两个结论：第一，诱导吸收的展宽是第一激发态振动冷却的结果()。其次，第二激发态()和第二激发态()之间的内转化率主要取决于相对曲线位移。后一点为溶剂和激发波长相关的实验提供了一个新的视角，并解除了文献中发现的几个研究之间的矛盾。
Carotenoids are fundamental building blocks of natural light harvesters with convoluted and ultrafast energy deactivation networks. In order to disentangle such complex relaxation dynamics, several studies focused on transient absorption measurements and their dependence on the pump wavelength. However, such findings are inconclusive and sometimes contradictory. In this study, we compare internal conversion dynamics in -carotene, pumped at the first, second, and third vibronic progression peak. Instead of employing data fitting algorithms based on global analysis of the transient absorption spectra, we apply a fully quantum mechanical model to treat the high-frequency symmetric carbon-carbon (C=C and C-C) stretching modes explicitly. This model successfully describes observed population dynamics as well as spectral line shapes in their time-dependence and allows us to reach two conclusions: Firstly, the broadening of the induced absorption upon excess excitation is an effect of vibrational cooling in the first excited state (). Secondly, the internal conversion rate between the second excited state () and crucially depends on the relative curve displacement. The latter point serves as a new perspective on solvent- and excitation wavelength-dependent experiments and lifts contradictions between several studies found in literature.