Sum-Frequency-Generation-Based Laser Sidebands for Tunable Femtosecond Raman Spectroscopy in the Ultraviolet
Sum-Frequency-Generation-Based Laser Sidebands for Tunable Femtosecond Raman Spectroscopy in the Ultraviolet
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DOI：
10.3390/app5020048
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发表时间：
2015-04
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影响因子：
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通讯作者：
Liangdong Zhu;Weimin Liu;Yanli Wang;Chong Fang
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文献类型：
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作者：
Liangdong Zhu;Weimin Liu;Yanli Wang;Chong Fang
飞秒受激拉曼光谱（FSRS）是一种新兴的分子结构动力学技术，通常在可见光到近红外范围内表征功能材料。为了扩大其应用，我们已经开发了一个多功能的FSRS设置在紫外区。我们使用了一个窄带，~400 nm的拉曼泵从一个自制的二次谐波带宽压缩器和可调谐的宽带探测脉冲从和频产生的级联四波混频（SFG-CFWM）激光边带在薄BBO晶体的组合。基态拉曼光谱的激光染料Quinolon 390在甲醇中，强烈吸收在~355 nm的系统研究作为一个标准样品，以提供以前不可用的振动域的光谱表征。通过选择不同阶次的SFG-CFWM边带作为探测脉冲，可以同时采集到斯托克斯和反斯托克斯拉曼谱。当在1317 cm−1处测量染料分子的芳环变形和环H摇摆模式时，402 nm拉曼泵浦的受激拉曼增益比550 nm拉曼泵浦的受激拉曼增益大21倍以上，表明在独特的UV-FSRS设置中有效地实现了预共振增强。在多功能和紧凑的光学设置中增加的可调谐性使FSRS能够更好地捕获在UV范围内吸收的光敏分子的瞬态构象快照。
Femtosecond stimulated Raman spectroscopy (FSRS) is an emerging molecular structural dynamics technique for functional materials characterization typically in the visible to near-IR range. To expand its applications we have developed a versatile FSRS setup in the ultraviolet region. We use the combination of a narrowband, ~400 nm Raman pump from a home-built second harmonic bandwidth compressor and a tunable broadband probe pulse from sum-frequency-generation-based cascaded four-wave mixing (SFG-CFWM) laser sidebands in a thin BBO crystal. The ground state Raman spectrum of a laser dye Quinolon 390 in methanol that strongly absorbs at ~355 nm is systematically studied as a standard sample to provide previously unavailable spectroscopic characterization in the vibrational domain. Both the Stokes and anti-Stokes Raman spectra can be collected by selecting different orders of SFG-CFWM sidebands as the probe pulse. The stimulated Raman gain with the 402 nm Raman pump is >21 times larger than that with the 550 nm Raman pump when measured at the 1317 cm−1 peak for the aromatic ring deformation and ring-H rocking mode of the dye molecule, demonstrating that pre-resonance enhancement is effectively achieved in the unique UV-FSRS setup. This added tunability in the versatile and compact optical setup enables FSRS to better capture transient conformational snapshots of photosensitive molecules that absorb in the UV range.