Excited States in Surface Photochemistry

9417866拟议的研究的目标是探测的能量和寿命的吸附物和基板激发态，并了解激发态弛豫过程和观察到的光化学产品之间的联系。 在泵浦-探测配置与可调谐激光器的双光子光电发射将被用来测量激发态的能量和寿命。 质谱仪和高分辨率电子能量损失谱仪提供了光化学产物的化学信息。 六硼化镧（100）的独特的低功函数用作其上吸附具有不同电子亲合势的分子的模型金属衬底。 带隙对弛豫过程的影响将在清洁和K-预吸附的氮化镓薄膜上进行研究。 将继续研究氧与一氧化碳共吸附在铂上的光化学和一氧化碳从硅上的光脱附。 表面光化学与表面激发态的弛豫密切相关。 表面激发态的信息是非常稀缺的，尽管它们在表面光化学的重要性。 光子吸收后的后续微观步骤在很大程度上是未知的，最多只能从最终产物的分布中获得。 它已被牢固地建立，两个最重要和最广泛的表面光化学机制是：1。吸附分子的直接电子激发，和2.衬底激发，随后是光生热载流子与吸附分子的相互作用。 拟议的研究的目标是探测的能量和寿命的吸附物和基板激发态，并了解激发态弛豫过程和观察到的光化学产品之间的连接。

9417866 The objectives of the proposed research are to probe the energies and lifetimes of the adsorbate and substrate excited states and to understand the connection between the excited state relaxation processes and the observed photochemical products. Two-photon photoemission in the pump-probe configuration with a tunable laser will be used to measure the energies and lifetimes of the excited states. A mass spectrometer and a high-resolution electron energy loss spectrometer provide chemical information on the photochemical products. The uniquely low work function of Lanthanum hexaboride(100) serves as a model metal substrate on which molecules with different electron affinities are adsorbed. The effects of a band gap on the relaxation processes will be investigated on clean and K-preadsorbed gallium nitride thin films. Studies on the photochemistry of oxygen coadsorbed with carbon monoxide on platinum and the photodesorption of carbon monoxide from silicon will be pursued. %%%% Surface photochemistry is intimately connected to the relaxation of excited states at the surface. Information on the excited states at surfaces is very scarce, despite their importance in surface photochemistry. The subsequent microscopic steps following absorption of photons are largely unknown and at best conjectured from the distribution of end products. It has been firmly established that the two most important and widespread mechanisms of surface photochemistry are: 1. direct electronic excitation of the adsorbed molecules, and 2. substrate excitation followed by interactions of photogenerated hot carriers with the adsorbed molecules. The objectives of the proposed research are to probe the energies and lifetimes of the adsorbate and substrate excited states and to understand the connection between the excited state relaxation processes and the observed photochemical products.