writer：Pengcheng Hu, Xu Li, Bolin Li, Xiaofeng Han, Furong Zhang, Keng C. Chou, Zhan Chen,* and Xiaolin Lu*
keywords：Coupling, Fs-SFG, Quantum beating, FID
source：期刊
specific source：J. Phys. Chem. Lett., 2018, 9 (17), pp 5167–5172
Issue time：2018年

在本文中，我们用量子拍频的方法解析了飞秒和频振动光谱(Fs-SFG)中时域和频域的光谱，得到了振动能量自由衰减对应的驰豫时间，首次用Fs-SFG区分了与电子振动耦合以及未耦合的苯环碳氢伸缩振动。相关技术可应用于微纳光学器件和分子器件的机制研究。由于振动驰豫反应了分子堆集的紧密程度，从基础科学层面，后续我们希望将这项技术应用于区分生物和高分子界面不同微环境的研究中。

感谢文章中多位同学对这一重要基础科学研究的贡献。胡鹏程、李柏霖和韩晓锋教授在实验操作上的贡献，胡鹏程、李旭、张芙荣、Chou教授对飞秒数据处理和程序写作上的贡献。感谢与Chou教授和Chen教授的讨论。正是与所有人的讨论让我们对飞秒技术有了逐步加深的认识。同时证明，依靠我们自己的努力，我们可以在非线性光谱和界面交叉领域做出重要的工作。

https://pubs.acs.org/doi/abs/10.1021/acs.jpclett.8b01765

https://pubs.acs.org/doi/suppl/10.1021/acs.jpclett.8b01765/suppl_file/jz8b01765_liveslides.mp4

Molecular couplings at interfaces play important roles in determining performance of nanophotonics and molecular electronics. In this letter, using femtosecond sum frequency generation (fs-SFG) to trace free-induction decay (FID) of vibrationally excited aromatic thiol molecules immobilized on metal with and without the bridged methylene group(s), metal surface free electron-coupled and uncoupled phenyl C-H stretching vibrational modes were identified, with dephasing times to be ~0.28 ps and ~0.60 ps, respectively. For thiols on Au with the bridged methylene group(s) (benzyl mercaptan and phenylethanethiol), both the coupled and uncoupled modes were observed; for thiol on Au without the bridged methylene group (thiophenol), only the coupled mode was observed. This indicates that the bridged methylene group(s) serving as a spacer can be used to adjust the molecular coupling between the phenyl vibration and surface free electrons. The experimental approach can be used to tune molecular couplings in advanced nanophotonics and molecular electronics.