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

通过对引入系统中的染料分子进行各种光学测量，广泛研究了无序系统中的超快动力学。研究发现，在室温溶液中，电子基态和激发态之间的光学消相发生在飞秒的时间尺度上，反映了周围原子的动力学，并且消相过程不能用简单的指数衰减来描述。本研究利用非相干光子回波和二阶光学过程研究了β-胡萝卜素在乙醇中的光学脱相。我们发现，即使在50 K时，也会在飞秒的时间尺度上发生消相。利用电子-声子相互作用的动力学模型对这些时域和频域测量结果进行了分析。由于该模型可以很好地再现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超快消相过程的一个很好的近似。此外，β-胡萝卜素分子的脱相过程近似表现为慢调制状态。从绝热势的角度看，得到的E_<LR>/ω0=8表明β-胡萝卜素分子中长共轭体系的电子-声子相互作用较强。飞秒时间尺度的减相本质上来自于这种相对强的耦合

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