Development of Interface-Selective Ultrafast Two-Dimensional Spectroscopy and Elucidation of the Structure of Water Interfaces

我们已经将外差检测振动和频率产生（HD-VSFG）光谱扩展到时间分辨测量。在此测量中，我们首先照射一个红外泵浦脉冲来振动激发分子，然后在足够的延迟时间后进行HD-VSFG测量，通过二阶非线性磁化率虚部的时间变化来跟踪超快振动动力学。我们将新开发的时间分辨HD-VSFG光谱应用于带电水界面，并首次成功测量了液体界面的飞秒时间分辨振动χ^<(2)>光谱。

We have extended heterodyne-detected vibrational sum-frequency generation(HD-VSFG) spectroscopy to time-resolved measurements. In this measurement, we first irradiate an infrared pump pulse to vibrationally excite the molecules and then performed a HD-VSFG measurement after an adequate delay time to trace the ultrafast vibrational dynamics through the temporal change of the imaginary part of the second order nonlinear susceptibility. We applied this newly-developed time-resolved HD-VSFG spectroscopy to charged water interfaces, and succeeded in measuring femtosecond time-resolved vibrationalχ^<(2)> spectra of liquid interfaces for the first time.