Vibrational spectroscopy and theory of alkali metal adsorption and co-adsorption on single-crystal surfaces

IF 8.2 1区 化学 Q1 CHEMISTRY, PHYSICAL
A. Politano , G. Chiarello , G. Benedek , E.V. Chulkov , P.M. Echenique
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引用次数: 56

Abstract

Alkali-metal (AM) atoms adsorbed on single-crystal surfaces are a model system for understanding the properties of adsorption. AM adsorption, besides introducing new overlayer vibrational states, induces significant modifications in the surface vibrational structure of the metal substrate. Several studies of the vibrational properties of AM on metal surfaces have been carried out in last decades. Most of these investigations have been performed for low coverages of AM in order to make the lateral interaction among co-adsorbates negligible. The adsorbed phase is characterized by a stretch (S) vibrational mode, with a polarization normal to the surface, and by other two modes polarized in the surface plane, known as frustrated translation (T) modes. The frequencies and intensities of these modes depend on the coverage, thus providing a spectroscopic signature for the characterization of the adsorbed phases.

The vibrational spectroscopy joined to an ab-initio theoretical analysis can provide useful information about surface charge re-distribution and the nature of the adatom–surface bond, establishing, e.g., its partial ionicity and polarization. Gaining this information implies a significant advancement in our knowledge on surface chemical bonds and on catalytic reactions occurring in AM co-adsorption with other chemical species. Hence, systematic studies of co-adsorption systems are essential for a more complete understanding of heterogeneous catalysis.

The two principal experimental techniques for studying the vibrations of AM adsorbed phases are high-resolution electron energy loss spectroscopy (HREELS) and inelastic helium atom scattering (HAS), the former being better suited to the analysis of the higher part of the vibrational spectrum, while the latter exploits its better resolution in the study of slower dynamics, e.g., T modes, surface acoustic phonons and diffusive phenomena. Concerning AM co-adsorption systems, reflection–absorption infrared spectroscopy (RAIRS) has been also used (as well as HREELS) for obtaining information on the influence of AM adsorption on the vibrational properties of co-adsorbates.

In this review an extended survey is presented over:

  • a)

    the existing HREELS and HAS vibrational spectroscopic studies for AM adsorbed on single-crystal metal surfaces;

  • b)

    the theoretical studies based on semi-empirical and ab-initio methods of vibrational structure of AM atoms on metal surfaces;

  • c)

    the vibrational (HREELS, RAIRS, TRSHG) characterization of the co-adsorption on metal surfaces of AM atoms with reactive species.

单晶表面碱金属吸附与共吸附的振动光谱与理论
碱金属(AM)原子吸附在单晶表面是了解吸附性质的一个模型系统。AM吸附除了引入新的上覆层振动状态外,还引起金属基板表面振动结构的显著改变。在过去的几十年里,对金属表面增材制造的振动特性进行了一些研究。大多数这些研究都是在AM的低覆盖率下进行的,以便使共吸附物之间的横向相互作用可以忽略不计。吸附相的特征是拉伸(S)振动模式,其极化方向与表面垂直,以及在表面平面上极化的其他两种模式,称为受挫平移(T)模式。这些模式的频率和强度取决于覆盖范围,从而为吸附相的表征提供了光谱特征。振动光谱与从头算理论分析相结合,可以提供有关表面电荷再分布和原子-表面键性质的有用信息,例如建立其部分离子性和极化。获得这些信息意味着我们在表面化学键和AM与其他化学物质共吸附的催化反应方面的知识取得了重大进展。因此,系统地研究共吸附系统对于更全面地了解多相催化是必不可少的。研究AM吸附相振动的两种主要实验技术是高分辨率电子能量损失谱(HREELS)和非弹性氦原子散射(HAS),前者更适合于分析振动谱的较高部分,而后者则利用其更好的分辨率研究较慢的动力学,例如T模式,表面声子和扩散现象。对于AM共吸附体系,反射-吸收红外光谱(RAIRS)也被用于(以及HREELS)获得AM吸附对共吸附物振动特性影响的信息。本文综述了单晶金属表面吸附AM原子的HREELS和HAS振动光谱研究;金属表面AM原子振动结构的半经验和从头算理论研究;AM原子与活性物质在金属表面共吸附的振动(HREELS, RAIRS, TRSHG)表征。
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来源期刊
Surface Science Reports
Surface Science Reports 化学-物理:凝聚态物理
CiteScore
15.90
自引率
2.00%
发文量
9
审稿时长
178 days
期刊介绍: Surface Science Reports is a journal that specializes in invited review papers on experimental and theoretical studies in the physics, chemistry, and pioneering applications of surfaces, interfaces, and nanostructures. The topics covered in the journal aim to contribute to a better understanding of the fundamental phenomena that occur on surfaces and interfaces, as well as the application of this knowledge to the development of materials, processes, and devices. In this journal, the term "surfaces" encompasses all interfaces between solids, liquids, polymers, biomaterials, nanostructures, soft matter, gases, and vacuum. Additionally, the journal includes reviews of experimental techniques and methods used to characterize surfaces and surface processes, such as those based on the interactions of photons, electrons, and ions with surfaces.
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