Torii Hajime
Department of Chemistry, School of Education, Shizuoka University, 836 Ohya, Shizuoka 422-8529, Japan.
J Phys Chem A. 2006 Apr 13;110(14):4822-32. doi: 10.1021/jp060014c.
A time-domain method for calculating polarized Raman and two-dimensional infrared (2D-IR) spectra that includes the effects of both the diagonal frequency modulations (of individual molecules in the system) and the off-diagonal (intermolecular) vibrational coupling is presented and applied to the case of the amide I band of liquid N,N-dimethylformamide. It is shown that the effect of the resonant off-diagonal vibrational coupling and the resulting delocalization of vibrational modes is clearly seen as the noncoincidence effect in the polarized Raman spectrum and some spectral features (especially as asymmetric intensity patterns) in the 2D-IR spectra. The type of 2D-IR spectra (concerning the polarization condition) most appropriate for observing this effect is discussed. On the basis of the agreement between the observed and calculated band profiles of the polarized Raman spectrum, the time dependence of the transient IR absorption anisotropy is also calculated. The method of evaluating the extent of delocalization of vibrational modes that is relevant to the features of these optical signals in the time and frequency domains is discussed. The nature of the molecular motions (concerning the liquid dynamics) that are effective on the diagonal frequency modulations is also examined.
提出了一种计算极化拉曼光谱和二维红外（2D-IR）光谱的时域方法，该方法考虑了（系统中单个分子的）对角频率调制和非对角（分子间）振动耦合的影响，并将其应用于液态N，N-二甲基甲酰胺的酰胺I带的情况。结果表明，共振非对角振动耦合的影响以及由此产生的振动模式离域，在极化拉曼光谱中表现为非重合效应，在二维红外光谱中表现为一些光谱特征（特别是不对称强度模式）。讨论了最适合观察这种效应的二维红外光谱类型（关于偏振条件）。基于极化拉曼光谱的观测和计算谱带轮廓之间的一致性，还计算了瞬态红外吸收各向异性的时间依赖性。讨论了评估与这些光信号在时域和频域中的特征相关的振动模式离域程度的方法。还研究了对角频率调制有效的分子运动性质（关于液体动力学）。
