Higher order off-resonat optical processes for homogeneous and inhomogeneous broadening of liquids

本文研究了非共振飞秒激光脉冲作用下分子体系凝聚态的非线性光学响应，探讨了液相的非均匀展宽和振动模式的非调和性。我们利用路径积分技术推导了非调和系统的五阶响应函数的解析表达式。应用这个方程，我们研究了非调和性和非均匀性之间的相互作用。推导了位移非调和系统的五阶响应函数，并将其应用于光子回波研究、泵浦探测实验和新开发的检测弱非调和电位的五阶实验。利用量子Fokker-Planck方程，研究了莫尔斯势系统的高阶光学过程。这个Fokker-Planck方程可以处理与高斯白噪声或高斯马尔可夫噪声相耦合的任何形状的势的分子系统。本文提出了用运动方程法计算三阶和五阶响应函数的方法，这些响应函数相当于分子坐标的二阶和三阶相关函数。假设以摩尔斯势为模型的铯二聚体的势面，以及极化率的线性和非线性坐标依赖关系，我们计算了不同温度和热浴耦合的三阶和五阶响应函数。通过绘制五阶光谱中涉及的两个时间演化周期，得到了信号的二维分布。这些二维剖面对电位和极化率的形状很敏感，即使在强阻尼情况下也是如此，并且取决于温度。这表明，在不同温度下进行的五阶二维光谱可以使我们获得势和极化率的信息。我们还提出了多态系统的福克-普朗克方程，并将其应用于位移莫尔斯振子系统。观察并讨论了它的光学斯塔克效应。少

The nonlinear optical response of a molecular system in the condensed phase subjected to a series of off-resonant femtosecond laser pulses has been studied to investigate inhomogeneous broadening of liquid states and anharmonicity of vibrational modes. We have derived analytical expressions of the 5th order response function for an anharmonic system using path-integral techniques. Applying this equation, we have studied the interplay between anharmonicity and inhomogeneity. The fifth-order response function for a displaced anharmonic system has been also derived and applied to study photon echo, pump-probe experiments and newly developed the fifth-order experiment which is designed to detect weak anharmonicity of potentials.Using a quantum Fokker-Planck equation, we have studied higher-order optical processes of Morse potential systems. This Fokker-Planck equation can treat a molecular system with any shape of potential coupled to a Gaussian-white or a Gaussian Markovian noise-bath. We … More have presented a procedure to calculate the third-and fifth-order response functions, which are equivalent to the second-and third-order correlation functions of the molecular coordinate, by way of the eq. of motion approach. Assuming the potential surface of a Cesium dimer, which is modeled by the Morse potential, and the linear and nonlinear coordinate dependence of the polarizability, we calculated the third-and fifth-order response functions for various temperatures and heat-bath couplings. By plotting two time-evolution period involved in the fifth-order spectroscopy, we obtained the two-dimensional profiles of the signals. These 2D profiles are sensitive for a shape of potential and polarizability, even for a strong damping case, and depend on the temperature. This indicates that fifth-order two-dimensional spectroscopy carried out for a different temperature allows us to access information of the potential and the polarizability. We have also presented the Fokker-Planck equation for multi-state systems and applied to the displaced Morse oscillators system. Optical Stark effects of it was observed and discussed. Less