Exploring a free energy landscape of frustrated system by means of multi-dimensional spectroscopes

自由能景观（FEL）是自由能的构象基态作为宏观变量的函数，已被广泛用于表征受挫系统的动力学行为，如玻璃和蛋白质。本研究的目的是通过探索用光学手段直接测量FEL的可能性来澄清一些用于描述受挫系统动力学的假设。为此，我们考虑一个由偶极子组成的系统，并采用一个简单的模型来降低自由度。我们通过生成所有可能的态来计算不同温度下的FEL，并通过构造所有态的主方程来研究FEL上的偶极子动力学。对于温度高于能量尺度的偶极-偶极相互作用。自由能景观具有二次型。当温度下降时，由于偶极子之间的相互作用受挫，在自由能谱上出现了小的缺口结构。通过这种方法，在马库斯理论失效的玻璃化转变温度以下获得了电子转移问题的新见解。充分利用了多维光谱的灵敏度来表征不同FEL下的动力学特性。在这里，我们计算了由偶极子算子的四体相关函数定义的红外、远红外或太赫兹光谱对应的二维信号。虽然线性吸收信号在时间上的衰减方式与FEL曲线相似，但二维信号在这些曲线中表现出明显的差异。这表明，我们可以通过改变二维光谱中涉及的二次值来区分FEL的轮廓。我们还开发了一种从分子动力学模拟的角度研究分子在多维光谱上的动力学的有效算法，它将现有的计算多维光谱的平衡和非平衡方法相结合。作为该模拟方法的应用，我们计算了各种分子液体的二维拉曼光谱。少

The free energy landscape (FEL) is the conformational substates of the free energy as a function of macroscopic variables, which has been widely used to characterize the dynamical behavior of frustrated systems such as glasses and proteins. The aim of this research is to clarify some of postulation used to describe the dynamics of a frustrated system by exploring a possibility to measure the FEL directly by optical means. For this purpose, we consider a system consists of dipoles and employ a simple model to reduce the degrees of freedom. We calculated the FEL at various temperatures by generating all possible states and studied the dynamics of dipoles on the FEL by constructing the master equation for all states. For temperatures higher than the energy scale of dipole-dipole interactions. The free energy landscapes have quadratic shape. When the temperature drops, small notched structures appear on the free energy profiles because of the frustrated interactions among dipoles. From thi … More s approach, the new insight for electron transfer problem was obtained below the glass transition temperature, where the Marcus theory breaks down. The sensitivity of multidimensional spectroscopy is fully used to characterize the dynamics upon different FEL. Here, we calculated two-dimensional signals corresponding to infrared, far IR or THz spectroscopy defined by the four-body correlation functions of dipole operators. While the linear absorption signals decay in time in a similar manner regardless of the FEL profiles, the 2D signals exhibit prominent differences in those profiles. This indicates that, we may differentiate the profiles of FEL by changing two-time valuables involved in 2D spectroscopy. We also developed an efficient algorithm to study the dynamics of molecules on mulitidimensional spectroscopy from molecular dynamics simulation approach, which hybridizes the existing equilibrium and nonequilibrium methods of calculating multidimensional spectroscopy. As an application of this simulation method, we calculated two-dimensional Raman spectrum of various molecular liquids. Less