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The electron-phonon interaction in liquid investigated by near-resonantly excited Ramen scattering spectra

通过近共振激发拉曼散射光谱研究液体中的电子-声子相互作用

基本信息

批准号：
11640315
负责人：
WATANABE Junji
金额：
$ 2.3万
依托单位：
Osaka University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1999
资助国家：
日本
起止时间：
1999 至 2000
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-11640315/
关键词：
optical dephasing secondary radiation Raman scattering electron-phonon interaction β-carotene

项目摘要

The ultrafast dynamics in disordered system has been extensively investigated by various optical measurements on dye molecules introduced into the system. It has been found that, in solutions at room temperature, the optical dephasing between the electronic ground and excited states occurs on the time scale of femtoseconds reflecting the dynamics of surrounding atoms and that the dephasing process cannot be described by a simple exponential decay. In this research, the optical dephasing of β-carotene in ethanol has been investigated by incoherent photon echo and the second-order optical processes. We found that the dephasing occured on the time scale of femtoseconds even at 50 K.These time-domain and frequency-domain measurements are analyzed by the dynamical model for the electron-phonon interaction. Since results of photon echo and second-order optical process are well reproduced by the model, we consider that the dynamical model with linear electron-phonon interaction is a good approximation for describing the ultrafast dephasing process in this system. In addition, the dephasing process of β-carotene molecule is approximately characterized by the slow modulation regime. From the viewpoint of adiabatic potential, the obtained value of E_<LR>/ω0=8 indicates that the electron-phonon interaction is relatively strong for the long conjugated system in β-carotene molecule. The dephasing in femtosecond time scale essentially comes from this relatively strong coupling

通过对引入系统的染料分子的各种光学测量，对无序系统中的超快动力学进行了广泛的研究。研究发现，在室温溶液中，电子基态和激发态之间的光学相移发生在飞秒时间尺度上，反映了周围原子的动力学，并且相移过程不能用简单的指数衰减来描述。在这项研究中，通过非相干光子回波和二阶光学过程研究了乙醇中β-胡萝卜素的光学相移。我们发现即使在 50 K 时，相移也发生在飞秒的时间尺度上。这些时域和频域测量结果通过电子-声子相互作用的动力学模型进行了分析。由于该模型很好地再现了光子回波和二阶光学过程的结果，因此我们认为具有线性电子声子相互作用的动力学模型是描述该系统中超快移相过程的良好近似。此外，β-胡萝卜素分子的相移过程大致具有慢调制机制的特征。从绝热势的角度来看，得到的E_<LR>/ω0=8的值表明β-胡萝卜素分子中的长共轭体系的电子-声子相互作用较强。飞秒时间尺度的相移本质上来自于这种相对较强的耦合