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Photochemical reaction at metal cluster surfaces as revealed by ultrafast vibrational spectroscopy

超快振动光谱揭示金属簇表面的光化学反应

基本信息

批准号：
10640570
负责人：
WATANABE Kazuya
金额：
$ 2.24万
依托单位：
The Graduate University for Advanced Studies (1999)Okazaki National Research Institutes (1998)
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1998
资助国家：
日本
起止时间：
1998 至 1999
项目状态：
已结题

项目摘要

We have investigated how intermediate species with excess energy contribute to various surface chemical reactions. We have mainly focused on the following topics :1. Reaction of carbon dioxide during the oxidation process of silicon surface :Carbon dioxide is known as a very stable molecule in gas phase. However, we have found that it is readily converted to carbonate species when it is adsorbed on silicon surface at low temperature and a surface oxidation procedure is conducted.2. Photodesorption of rare gas atoms on silicon surfacesRare gas atoms (Kr, Xe) weakly adsorb on a Si(100) surface. We found for the first time that these adsorbates are desorbed by the irradiation of photos whose wavelength range from near infrared to uv. It is revealed that the desorption occurs via energy transfer from surface hot phonon which is excited by charge recombination of photocarriers at surface states. We also found that the desorption mechanism changes to that involves charge transfer state between the substrate and the adsorbate by surface modification with oxygen or deuterium.3. Photochemistry of oxygen adsorbed on Ag(110)Photochemistry of oxygen atoms on Ag(110) has been investigated. The chemisorbed oxygen atoms are removed by uv light irradiation. It is found that slight amount of carbon atom in the surface region is necessary for the reaction. Wavelength dependence of photo-yield indicates that the phtogenerated hot-electron plays a crucial role in this reaction.4. Development of the light source for time resolved vibrational spectroscopyTHz electro-magnetic field radiation from femtosecond laser irradiated InAs surface has been investigated. Under an ultra-high vacuum condition, an effect of the surface cleanness and a temperature dependence of the THz radiation were examined. It was found that the THz radiation intensity was enhanced up to two-times by surface cleaning and up to 4 times by temperature lowering to 50 K compared to that at room temperature in air.

我们已经研究了具有过剩能量的中间物种如何有助于各种表面化学反应。我们主要集中在以下几个方面：1.二氧化碳在硅表面氧化过程中的反应：众所周知，二氧化碳在气相中是一种非常稳定的分子。然而，我们发现，当它在低温下吸附在硅表面并进行表面氧化过程时，很容易转化为碳酸盐物种.稀有气体原子在Si（100）表面的光脱附研究我们首次发现这些吸附物在近红外到紫外光的照射下会发生脱附。结果表明，脱附是通过表面态光生载流子的电荷复合激发的表面热声子的能量转移发生的。我们还发现，通过氧气或氘的表面改性，脱附机制转变为涉及衬底和吸附质之间的电荷转移状态.研究了氧原子在Ag（110）表面上的光化学。化学吸附的氧原子通过紫外光照射除去。结果表明，反应需要少量的表面碳原子。光产额的波长依赖性表明，光生热电子在该反应中起着关键作用.时间分辨振动光谱光源的研制研究了飞秒激光辐照InAs表面产生的THz电磁场辐射。在超高真空条件下，表面清洁度的影响和太赫兹辐射的温度依赖性进行了检查。结果发现，太赫兹辐射强度提高了2倍，通过表面清洁和高达4倍的温度降低到50 K相比，在室温下的空气中。