Vibrational Line Broadening Mechanisms for Molecules Adsorbed on Metal Surfaces

该项目属于分析和表面化学的一般领域，以及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)测量了各种吸附在金属表面的分子的高分辨振动光谱。红外光谱的范围将扩大：1)研究吸附-衬底振动；2)表征低至10K温度下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-无序相变对吸附线形的影响。要研究的化学体系包括铂和镍单晶面上的分子物种三氟化磷、一氧化碳和乙叉。振动光谱的固有线型包含关于吸附-吸附相互作用的信息，振动与其他模式耦合的程度，以及其他振动模式的下限。这项研究将采用的广泛温度范围和冻结声子机制的可能性将允许在各种相互竞争的谱线加宽机制之间进行区分。

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.