Assessing the Gold Standard: The Complex Vibrational Nonlinear Susceptibility of Metals

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• 作者：Paul A. Covert ; Dennis K. Hore
• 刊名：Journal of Physical Chemistry C
• 出版年：2015
• 出版时间：January 8, 2015
• 年：2015
• 卷：119
• 期：1
• 页码：271-276
• 全文大小：299K
• ISSN：1932-7455

文摘

Sum-frequency generation techniques can offer molecular-level, structural details of surfaces and interfaces. The incorporation of a metallic layer, either exposed or buried, is frequently used to provide a nonvibrationally resonant reference to which the phase of the resonant responses may be compared. This in turn provides further structural information, such as the polarity of interfacial groups. Because the phase of the metal depends strongly on factors that alter the electronic structure of the interface, such as the wavelength of the visible beam, chemical bonding, and surface coverage, it is beneficial to characterize the phase of the nonresonant response. A direct measurement of the absolute phase of a commonly prepared model hydrophobic surface, 1-octadecanethiol bound to gold, is presented and compared with relative phase measurements. Assignment of the phase of metallic samples requires careful consideration of the effects of the local field upon phase in both the near and far fields. We have outlined an approach that is suitable for the characterization of any dielectric or metal surface.