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

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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.