利用液态水的三阶红外与五阶红外-拉曼过程模拟二维相关光谱
Simulating two-dimensional correlation spectroscopies with third-order infrared and fifth-order infrared--Raman processes of liquid water
AI总结：
本研究采用多模布朗振子模型与DHEOM-MLWS方法，计算液态水的三阶二维红外和五阶二维红外-拉曼光谱，以探究其分子间与分子内非谐耦合特性。
摘要：
为探究测量体相水的分子间与分子内非谐耦合的可能性，我们计算了以光学可观测量的四体关联函数表示的三阶二维（2D）红外（IR）光谱以及五阶二维IR-IR-拉曼-拉曼光谱。为此，我们采用了由四个相互作用的非谐振子构成的多模布朗振子模型，这些振子与各自的热浴强耦合。我们考虑了系统-热浴相互作用的非线性，以描述热弛豫和振动失相。随后，我们使用混合刘维尔-维格纳空间中的离散化层级运动方程（DHEOM-MLWS），在非马尔可夫和非微扰区域中以严格的方式计算了线性和非线性光谱。计算得到的伸缩-弯曲、弯曲- librational（平动-转动）、伸缩-librational以及伸缩-平动模式的二维光谱包含各种正负峰，展现了有限温度下热弛豫和失相过程中分子间与分子内模式-模式相互作用的本质细节。
英文摘要：
To investigate the possibility of measuring the intermolecular and intramolecular anharmonic coupling of balk water, we calculate third-order two-dimensional (2D) infrared (IR) spectra and fifth-order 2D IR-IR-Raman-Raman spectra expressed in terms of four-body correlation functions of optical observables. For this purpose, a multimode Brownian oscillator model of four interacting anharmonic oscillators strongly coupled to their respective heat baths is employed. The nonlinearity of the system-bath interactions is considered to describe thermal relaxation and vibrational dephasing. The linear and nonlinear spectra are then computed in a non-Markovian and nonperturbative regime in a rigorous manner using the discretized hierarchical equations of motion in mixed Liouville-Wigner space (DHEOM-MLWS). The calculated 2D spectra for stretching-bending, bending-librational, stretching-librational, and stretching-translational modes consist of various positive and negative peaks exhibiting essential details of the intermolecular and intramolecular mode-mode interactions under thermal relaxation and dephasing at finite temperature.
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