Multiplexed polarization spectroscopy: measuring surface hyperpolarizability orientation.
Multiplexed polarization spectroscopy: measuring surface hyperpolarizability orientation.
复制标题
多重偏振光谱：测量表面超极化方向。
作者：
M. Shultz;P. Bisson;H. Groenzin;Irene Li
可见光和频发生（SFG）作为表面探针的使用越来越多，特别是对于液体界面，因为它们可以接受很少的替代探针。然而，解释SFG数据以获得表面上的分子水平配置仍然是一个挑战。本文报道了一种分析和解释SFG数据的技术--偏振角零或PAN-SFG。PAN-SFG能够容易地识别表面切向和纵向超极化率的比率-超极化率方向-以及由于基板和实验几何形状而与光学因素分离的这些组件之间的相位关系。表面光学因子的分离导致零角和表面物质偏振之间的直接联系。如果拉曼极化率也是已知的，那么PAN-SFG分析，像以前报道的零技术，提供了一个非常准确的取向。此外，报告的偏振角，相移分析，使非共振背景偏振的共振信号的分离。除了定向，PAN-SFG可用于去卷积重叠共振并识别偶极子响应以外的分量。本文报告了两个系统的PAN-SFG，提供了更深入的了解。乙腈-水的混合物先前被报道在7摩尔%时发生相变，归因于取向的突然变化。PAN-SFG表明乙腈产生经典的偶极响应，并提供了令人信服的证据表明，乙腈的配置作为浓度的函数保持不变。另一种模型的相变。像许多水溶液系统一样，冰的氢键区域的SFG光谱由广泛和重叠的特征组成;先前用PAN-SFG识别的特征。在这里，使用PAN-SFG分析表明，其中最红的，在3098 cm（-1）的功能，包含一个显着的四极贡献，随着温度的降低而增长。四极和它的温度依赖性被用来分配3098 cm（-1）的功能，双层缝合氢键。这是第一个明确的分配在氢键区域的水。
Infrared-visible sum frequency generation (SFG) has seen increasing usage as a surface probe, particularly for liquid interfaces since they are amenable to few alternate probes. Interpreting the SFG data to arrive at a molecular-level configuration on the surface, however, remains a challenge. This paper reports a technique for analyzing and interpreting SFG data--called polarization-angle null or PAN-SFG. PAN-SFG enables ready identification of the ratio of the surface tangential and longitudinal hyperpolarizabilities--the hyperpolarizability direction--as well as the phase relationship between these components separated from the optical factors due to the substrate and experimental geometry. Separation of the surface optical factors results in an immediate connection between the null angle and the surface species polarization. If the Raman polarizability is also known, then PAN-SFG analysis, like the previously reported null techniques, provides a very accurate orientation. In addition, the reported polarization-angle, phase-shift analysis enables facile separation of the nonresonant background polarization from that of the resonant signal. Beyond orientation, PAN-SFG can be used to deconvolute overlapping resonances and identify components beyond a dipole response. This paper reports PAN-SFG for two systems providing deeper insight into both. An acetonitrile-water mixture was previously reported to undergo a phase transition at 7 mol %, attributed to a sudden change in orientation. PAN-SFG demonstrates that acetonitrile generates a classic dipole response and provides compelling evidence that the acetonitrile configuration remains constant as a function of concentration. An alternate model for the phase transition is presented. Like many aqueous systems, the SFG spectrum of the hydrogen-bonded region of ice consists of broad and overlapping features; features previously identified with PAN-SFG. Here PAN-SFG analysis is used to show that the reddest of these, the feature at 3098 cm(-1), contains a significant quadrupole contribution that grows as the temperature is lowered. The quadrupole and its temperature dependence are used to assign the 3098 cm(-1) feature to bilayer-stitching-hydrogen bonds. This is the first definitive assignment in the hydrogen-bonded region of water.
光解碳单氧基细胞色素 c 氧化酶（细胞色素 aa3）的时间分辨磁圆二色光谱。
影响因子：
3.4
作者：
Goldbeck,RA;Dawes,TD;Einarsdottir,O;Woodruff,WH;Kliger,DS
通讯作者：
Kliger,DS