Interpretation of the THz-THz-Raman Spectrum of Bromoform
Interpretation of the THz-THz-Raman Spectrum of Bromoform
复制标题
三溴甲烷的太赫兹-太赫兹-拉曼光谱解读
DOI：
10.1021/acs.jpca.9b05165
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发表时间：
2019
期刊：
影响因子：
--
通讯作者：
Miller, Thomas F.
中科院分区：
文献类型：
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作者：
Magdău, Ioan B.;Mead, Griffin J.;Blake, Geoffrey A.;Miller, Thomas F.
非线性太赫兹-太赫兹-拉曼（TTR）液体光谱为研究和理解凝聚相化学动力学提供了新的可能性。虽然TTR光谱携带丰富的信息，正在研究的系统，响应编码在一个三点相关函数，包括偶极子和极化率元素。理论方法对于解释实验结果是必要的。在这项工作中，我们研究了溴仿，一个极化的分子具有很强的TTR响应的液相动力学。以前的工作的基础上约化密度矩阵（RDM）模拟表明，非常大的多量子偶极子矩阵元素需要了解溴仿的测量光谱。在这里，我们证明了相对于参考脉冲的时间坐标的自洽定义导致简化的实验光谱。此外，我们分析得出的RDM模型的参数化，通过整合偶极子和极化率元素的正常模式的第4阶，我们执行反演对称性的计算，通过数值取消的组件的响应，甚至相对于字段。由此产生的分析消除了需要调用大的多量子偶极矩阵元素，以适应实验光谱，相反，实验光谱恢复使用RDM模拟与偶极矩阵参数，是在独立的从头计算。TTR签名耦合分子内振动模式的基本解释保持不变，从以前的工作。
Nonlinear THz-THz-Raman (TTR) liquid spectroscopy offers new possibilities for studying and understanding condensed-phase chemical dynamics. Although TTR spectra carry rich information about the systems under study, the response is encoded in a three-point correlation function comprising of both dipole and polarizability elements. Theoretical methods are necessary for the interpretation of the experimental results. In this work, we study the liquid-phase dynamics of bromoform, a polarizable molecule with a strong TTR response. Previous work based on reduced density matrix (RDM) simulations suggests that unusually large multiquanta dipole matrix elements are needed to understand the measured spectrum of bromoform. Here, we demonstrate that a self-consistent definition of the time coordinates with respect to the reference pulse leads to a simplified experimental spectrum. Furthermore, we analytically derive a parametrization for the RDM model by integrating the dipole and polarizability elements to the 4th order in the normal modes, and we enforce inversion symmetry in the calculations by numerically canceling the components of the response that are even with respect to the field. The resulting analysis eliminates the need to invoke large multiquanta dipole matrix elements to fit the experimental spectrum; instead, the experimental spectrum is recovered using RDM simulations with dipole matrix parameters that are in agreement with independent ab initio calculations. The fundamental interpretation of the TTR signatures in terms of coupled intramolecular vibrational modes remains unchanged from the previous work.