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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Optical Nonlinearities and Molecular Kinetics of Hypocrellin A
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Optical Nonlinearities and Molecular Kinetics of Hypocrellin A

机译：Hypocrellin A的光学非线性和分子动力学

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摘要

Optical nonlinearities (including nonlinear absorption and nonlinear refraction) and the temporal properties of the nonlinear refraction of hypocrellin A (HA) in its resonant region have been investigated by using single-beam Z-scan and time-resolved two-color Z-scan techniques with picosecond pulses. The reverse saturable absorption effect can be attributed to the efficient absorption of excited states of both the normal and tautomeric forms, S_1 and S'_1, with the contribution of S_1 as the dominant mechanism. The change of the refractive index of HA increases with increasing irradiance I_0 at low irradiances (<5 GW/cm~2), while it hardly changes with I_0 at high irradiances. The explanation for such an experimental phenomenon is that the averaged population densities of both S_1 and S'_1 increase with I_0 at low irradiance, while those of these two states become saturated at high irradiance. The refractive nonlinearities exhibit a very slowly decaying tail, which is attributed to the contributions of S_1, S'_1, and the triplet state of the normal form, T_1, and is dependent on the rise times and lifetimes of these intermediate states. The kinetic model for HA allows for the determination of the absorption cross sections of the ground state of the normal form of HA S_0, the ground state of its tautomer S'_0, the excited state of its tautomer S'_1, and the refractive nonlinearities of S_1, S'_1, and T_1. The close match between the theory and experiment not only shows the completeness of the five-level kinetic model but also demonstrates the close relationship between the optical nonlinearities of HA and the dynamics involved in excited-state intramolecular proton transfer.
机译：通过使用单光束Z扫描和时间分辨双色Z扫描技术研究了光皮蛋白的非线性（包括非线性吸收和非线性折射）及其在共振区域中的hypercrellin A（HA）的非线性折射的时间特性。皮秒脉冲。反向饱和吸收效应可以归因于正常和互变异构形式S_1和S'_1的激发态的有效吸收，而S_1的贡献是主要机制。在低辐照度（<5 GW / cm〜2）下，HA的折射率变化随辐照度I_0的增加而增加，而在高辐照度下，HA的折射率变化几乎不随I_0的变化而变化。对于这种实验现象的解释是，在低辐照度下，S_1和S'_1的平均人口密度随I_0的增加而增加，而在高辐照度下，这两种状态的平均人口密度都趋于饱和。折射非线性表现出非常缓慢衰减的尾巴，这归因于S_1，S'_1和正态形式T_1的三重态，并且取决于这些中间态的上升时间和寿命。 HA的动力学模型可以确定HA S_0的标准形式的基态，其互变异构体S'_0的基态，其互变异构体S'_1的激发态以及折射非线性的吸收截面。 S_1，S'_1和T_1。理论与实验的紧密匹配不仅表明了五能级动力学模型的完备性，而且还证明了HA的光学非线性与激发态分子内质子转移所涉及的动力学之间的密切关系。

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