Vibrational Line Broadening Mechanisms for Molecules Adsorbed on Metal Surfaces

这个项目是在分析和表面化学的一般领域和在表面振动光谱学的子领域。利用傅里叶变换红外反射吸收光谱（FT-IRAS）测量金属表面吸附的各种分子的高分辨率振动光谱。IRAS的局限性将得到扩展：1)研究吸附物-衬底振动；2)表征低至10 K时振动线形的温度依赖性；3)表征泛音的线形；4)表征和分析有序-无序相变对吸附质线形的影响。要研究的化学体系包括铂和镍单晶面上的三氟化磷、一氧化碳和乙炔分子。振动谱的本征线形包含了吸附质与吸附质的相互作用、与其它振型的耦合程度以及其它振型的下界等信息。广泛的温度范围将被用于这项研究和冻结声子机制的可能性，将允许区分各种竞争机制的线拓宽。

This project is in the general area of analytical and surface chemistry and in the subfield of surface vibrational spectroscopy. High resolution vibrational spectra of a variety of molecular species adsorbed on metal surfaces will be measured using Fourier transform infrared reflection-absorption spectroscopy (FT-IRAS). The limits of IRAS will be extended: 1) to study adsorbate-substrate vibrations; 2) to characterize the temperature dependence of vibrational line shapes at temperatures as low as 10 K; 3) to characterize the line shapes of overtones; 4) to characterize and analyze the influence of order-disorder phase transitions on adsorbate lineshapes. Chemical systems to be studied include the molecular species phosphorus trifluoride, carbon monoxide and ethylidyne on single-crystal faces of platinum and nickel. The intrinsic lineshapes of vibrational spectra contain information on adsorbate-adsorbate interactions, the extent of vibrational coupling to other modes, and the lower bound of other vibrational modes. The wide range of temperatures that will be employed in this study and the possibility of freezing out phonon mechamisms will permit discrimination among various competing mechanisms of line broadening.