Time-Domain SFG Spectroscopy Using Mid-IR Pulse Shaping: Practical and Intrinsic Advantages
Time-Domain SFG Spectroscopy Using Mid-IR Pulse Shaping: Practical and Intrinsic Advantages
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DOI：
10.1021/jp200757x
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发表时间：
2011-03-24
影响因子：
3.3
通讯作者：
Zanni, Martin T.
中科院分区：
文献类型：
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作者：
Laaser, Jennifer E.;Xiong, Wei;Zanni, Martin T.
和频(SFG)光谱是表面科学中普遍存在的一种工具。它提供了红外跃迁频率和线形，可以探测分子在界面上的结构和环境。在本文中，我们将从多维光谱学社区学到的技术应用于SFG光谱学。我们实现了平衡外差检测，以去除散射和本振背景。异步法还通过获取频谱的实部和虚部来分离共振和非共振信号。我们利用中红外脉冲整形来控制中红外泵浦脉冲的相位和延迟。脉冲整形允许在旋转帧中进行数据采集的相位循环和额外的背景相减。我们还展示了时域数据采集，这是一种傅里叶变换技术，在信号吞吐量、频率分辨率和线形精度方面比现有的频域方法具有许多优势。为了演示时域SFG光谱，我们研究了金表面的芳基异氰化物，发现该体系具有不均匀的结构分布，这与计算结果一致，但这是以前的频域SFG研究所不能解决的。能够快速、主动地操纵SFG脉冲序列中的中红外脉冲，使新的实验和更准确的光谱成为可能。
Sum-frequency generation (SFG) spectroscopy is a ubiquitous tool in the surface sciences. It provides infrared transition frequencies and line shapes that probe the structure and environment of molecules at interfaces. In this article, we apply techniques learned from the multidimensional spectroscopy community to SFG spectroscopy. We implement balanced heterodyne detection to remove scatter and the local oscillator background. Heterodyning also separates the resonant and nonresonant signals by acquiring both the real and imaginary parts of the spectrum. We utilize mid-IR pulse shaping to control the phase and delay of the mid-IR pump pulse. Pulse shaping allows phase cycling for data collection in the rotating frame and additional background subtraction. We also demonstrate time-domain data collection, which is a Fourier transform technique, and has many advantages in signal throughput, frequency resolution, and line shape accuracy over existing frequency domain methods. To demonstrate time-domain SFG spectroscopy, we study an aryl isocyanide on gold, and find that the system has an inhomogeneous structural distribution, in agreement with computational results, but which was not resolved by previous frequency-domain SFG studies. The ability to rapidly and actively manipulate the mid-IR pulse in an SFG pules sequence makes possible new experiments and more accurate spectra.