Photoexcitation of adsorbates on metal surfaces: one-step or three-step.
Photoexcitation of adsorbates on metal surfaces: one-step or three-step.
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DOI：
10.1063/1.4746801
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发表时间：
2012-09
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影响因子：
--
通讯作者：
H. Petek
中科院分区：
文献类型：
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作者：
H. Petek
在本文中，我们讨论了在分子覆盖的金属表面引发表面光化学的光-物质相互作用。表面光化学的热电子机制，即金属表面对光的吸收形成电子-空穴对，热电子通过吸附物质的未被占据的共振散射，启动导致光化学的核动力学，已被广泛接受。然而，分子表面电子结构和光激发动力学的超快光谱测量对热电子机制提供的支持很少。相反，在大多数情况下，吸附共振是通过光诱导衬底到吸附电荷转移来激发的。基于最近通过光学相位和动量分辨双光子光电子能谱测量相干态在吸附体光激发中的作用的研究，我们严格地考察了热电子机制，并提出了一种基于电子从衬底到吸附体光激发的直接电荷转移的描述。这种更严格的量子力学描述的优点是，它揭示了衬底和吸附的材料属性以及它们的相互作用如何影响光激发的频率相关概率，以及最终如何利用光来探测和控制表面的飞秒化学。
In this essay we discuss the light-matter interactions at molecule-covered metal surfaces that initiate surface photochemistry. The hot-electron mechanism for surface photochemistry, whereby the absorption of light by a metal surface creates an electron-hole pair, and the hot electron scatters through an unoccupied resonance of adsorbate to initiate nuclear dynamics leading to photochemistry, has become widely accepted. Yet, ultrafast spectroscopic measurements of molecule-surface electronic structure and photoexcitation dynamics provide scant support for the hot electron mechanism. Instead, in most cases the adsorbate resonances are excited through photoinduced substrate-to-adsorbate charge transfer. Based on recent studies of the role of coherence in adsorbate photoexcitation, as measured by the optical phase and momentum resolved two-photon photoemission measurements, we examine critically the hot electron mechanism, and propose an alternative description based on direct charge transfer of electrons from the substrate to adsorbate. The advantage of this more quantum mechanically rigorous description is that it informs how material properties of the substrate and adsorbate, as well as their interaction, influence the frequency dependent probability of photoexcitation and ultimately how light can be used to probe and control surface femtochemistry.