Time-Resolved Studies of Coherent Surface Optical Phonons and Low Frequency Adsorbate-Substrate Vibrations

在化学系实验物理化学计划的这个项目中，在多学科活动办公室的仪器支持下，Harry Tom教授将开发和表征一种新型的表面光学声子和低频吸附-衬底振动模式的相干光谱。这里的工作将建立在大量表面上创建和检测相干声子振荡的一般机制。确定这些低频模式的能量和退相弛豫时间是表面动力学中的一个突出问题。半导体(砷化镓和硅)和金属(铜和碱覆盖的铜)表面都将被检查。即将发展的时间分辨表面二次谐波产生信号(TRSHG)技术与现有的光谱技术相比具有更好的光谱分辨率和更高的信噪比，是研究表面声子的唯一相干技术。

In this project of the Experimental Physical Chemistry Program in the Chemistry Division with support for instrumentation from the Office of Multidisciplinary Activities, Prof. Harry Tom will develop and characterize a new type of coherent spectroscopy for surface optical phonons and for low frequency adsorbate-substrate vibrational modes. The work here will establish general mechanisms for creating and detecting coherent phonon oscillations on a large number of surfaces. Establishing the energy and dephasing relaxation times for these low frequency modes is an outstanding problem in surface dynamics. Both semiconductor (GaAs and Si) and metal (Cu and alkali-covered Cu) surfaces will be examined. The time-resolved surface second-harmonic generation signal (TRSHG) technique to be developed here has several advantages over existing spectroscopic techniques, such as better spectral resolution and higher signal-to-noise ratio, and it is the only coherent technique for studying surface phonons.