Analysis of 2D THz-Raman spectroscopy using a non-Markovian Brownian oscillator model with nonlinear system-bath interactions
Analysis of 2D THz-Raman spectroscopy using a non-Markovian Brownian oscillator model with nonlinear system-bath interactions
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DOI：
10.1063/1.4917033
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发表时间：
2015-06-07
影响因子：
4.4
通讯作者：
Tanimura, Yoshitaka
中科院分区：
文献类型：
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作者：
Ikeda, Tatsushi;Ito, Hironobu;Tanimura, Yoshitaka
我们利用具有线性-线性（LL）和平方-线性（SL）系统浴相互作用的布朗振子（BO）模型来探索和描述分子间振动的作用，我们使用它来分析通过分子动力学（MD）模拟获得的二维（2D）太赫兹-拉曼光谱。除了线性红外吸收（1D IR）外，我们还使用平衡非平衡混合MD模拟计算了液体甲酰胺，水和甲醇的二维拉曼-太赫兹，太赫兹-拉曼-太赫兹和太赫兹-太赫兹-拉曼信号。将计算得到的1D IR和2D太赫兹拉曼信号与通过使用具有非摄动和非马尔可夫噪声的分层Fokker-Planck方程应用的LL+SL BO模型得到的结果进行了比较。我们发现，从MD模拟中获得的信号的二维轮廓的所有定性特征都可以用LL+SL BO模型再现，表明该模型捕获了分子间运动的基本特征。我们从非调和性、非线性极化率和消相时间等方面分析了拟合的二维轮廓。利用光学刘维尔路径分析了振动运动回波峰和平行于探头方向的细长回波峰的来源。(C) 2015 AIP出版有限责任公司
We explore and describe the roles of inter-molecular vibrations employing a Brownian oscillator (BO) model with linear-linear (LL) and square-linear (SL) system-bath interactions, which we use to analyze two-dimensional (2D) THz-Raman spectra obtained by means of molecular dynamics (MD) simulations. In addition to linear infrared absorption (1D IR), we calculated 2D Raman-THz-THz, THz-Raman-THz, and THz-THz-Raman signals for liquid formamide, water, and methanol using an equilibrium non-equilibrium hybrid MD simulation. The calculated 1D IR and 2D THz-Raman signals are compared with results obtained from the LL+SL BO model applied through use of hierarchal Fokker-Planck equations with non-perturbative and non-Markovian noise. We find that all of the qualitative features of the 2D profiles of the signals obtained from the MD simulations are reproduced with the LL+SL BO model, indicating that this model captures the essential features of the inter-molecular motion. We analyze the fitted 2D profiles in terms of anharmonicity, nonlinear polarizability, and dephasing time. The origins of the echo peaks of the librational motion and the elongated peaks parallel to the probe direction are elucidated using optical Liouville paths. (C) 2015 AIP Publishing LLC.