表面和频生成振动光谱 (SFG-VS) 中的定量光谱和取向分析,International Reviews in Physical Chemistry

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表面和频生成振动光谱 (SFG-VS) 中的定量光谱和取向分析
International Reviews in Physical Chemistry ( IF 2.5 ) Pub Date : 2005-04-01 , DOI: 10.1080/01442350500225894
Hong-Fei Wang * , Wei Gan † ‡ , Rong Lu † ‡ § , Yi Rao † ‡ ¶ , Bao-Hua Wu †

和频生成振动光谱 (SFG-VS) 已被证明是研究分子结构和构象以及分子界面动力学的一种独特有效的光谱技术。然而，将 SFG-VS 应用于复杂分子界面的能力受到从 SFG-VS 实验中提取定量信息的能力的限制。在这篇综述中，我们尝试评估 SFG-VS 在定量定向和光谱分析中的局限性、问题和技术以及方法。基于这些评估，我们还尝试总结 SFG-VS 中定量定向和光谱分析方法学的最新进展，以及它们在详细分析各种蒸汽/净液体界面的 SFG-VS 数据中的应用。给出了偏振零角（PNA）方法的严格公式，以准确确定定向参数 D = ⟨cos θ ⟩/⟨cos3 θ⟩，并将 PNA 方法与常用的偏振强度比（PIR）方法进行比较进行了讨论。根据如何优化实验安排以有效地从 SFG-VS 实验中提取关键信息，还审查了 SFG-VS 强度的偏振和入射角依赖性。讨论了分子层中局部场因子的值和模型。为了检验键极化导数模型的有效性和局限性，分子超极化张量的一般表达式及其与 C 3 v 的键极化导数模型的表达式，C 2 v 和C ∞ v 分子群在两个附录中给出。我们表明，键极化率导数模型可以定量描述在不同极化下蒸汽/纯液体界面的 SFG-VS 光谱中观察到的强度的许多方面。使用 SFG-VS 中的偏振分析，开发了用于分配 SFG-VS 光谱的偏振选择规则或指南。使用选择规则，指定了蒸气/二醇和蒸气/正醇（n∼1-8）界面的 SFG-VS 光谱，以及一些模糊和混乱，以及它们在以前的 IR 和拉曼光谱中的含义分配，进行了适当的讨论。使用偏振选择规则分配 SFG-VS 光谱的能力使 SFG-VS 不仅是一种有效且有用的界面研究振动光谱技术，也是一般凝聚相研究中的一种补充振动光谱方法。这些发展将为 SFG-VS 中的定量定向和光谱分析奠定更坚实的基础。本综述中讨论的配方、概念和问题有望在未来的分子界面研究中找到广泛的应用。

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Quantitative spectral and orientational analysis in surface sum frequency generation vibrational spectroscopy (SFG-VS)

Sum frequency generation vibrational spectroscopy (SFG-VS) has been proven to be a uniquely effective spectroscopic technique in the investigation of molecular structure and conformations, as well as the dynamics of molecular interfaces. However, the ability to apply SFG-VS to complex molecular interfaces has been limited by the ability to abstract quantitative information from SFG-VS experiments. In this review, we try to make assessments of the limitations, issues and techniques as well as methodologies in quantitative orientational and spectral analysis with SFG-VS. Based on these assessments, we also try to summarize recent developments in methodologies on quantitative orientational and spectral analysis in SFG-VS, and their applications to detailed analysis of SFG-VS data of various vapour/neat liquid interfaces. A rigorous formulation of the polarization null angle (PNA) method is given for accurate determination of the orientational parameter D = ⟨cos θ ⟩/⟨cos3 θ⟩, and comparison between the PNA method with the commonly used polarization intensity ratio (PIR) method is discussed. The polarization and incident angle dependencies of the SFG-VS intensity are also reviewed, in the light of how experimental arrangements can be optimized to effectively abstract crucial information from the SFG-VS experiments. The values and models of the local field factors in the molecular layers are discussed. In order to examine the validity and limitations of the bond polarizability derivative model, the general expressions for molecular hyperpolarizability tensors and their expression with the bond polarizability derivative model for C 3 v , C 2 v and C ∞ v molecular groups are given in the two appendixes. We show that the bond polarizability derivative model can quantitatively describe many aspects of the intensities observed in the SFG-VS spectrum of the vapour/neat liquid interfaces in different polarizations. Using the polarization analysis in SFG-VS, polarization selection rules or guidelines are developed for assignment of the SFG-VS spectrum. Using the selection rules, SFG-VS spectra of vapour/diol, and vapour/n-normal alcohol (n∼ 1–8) interfaces are assigned, and some of the ambiguity and confusion, as well as their implications in previous IR and Raman assignment, are duly discussed. The ability to assign a SFG-VS spectrum using the polarization selection rules makes SFG-VS not only an effective and useful vibrational spectroscopy technique for interface studies, but also a complementary vibrational spectroscopy method in general condensed phase studies. These developments will put quantitative orientational and spectral analysis in SFG-VS on a more solid foundation. The formulations, concepts and issues discussed in this review are expected to find broad applications for investigations on molecular interfaces in the future.

更新日期：2005-04-01

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