Cavity ring-down spectroscopy on size-selected, supported clusters

本课题旨在利用倏逝波腔衰荡光谱对光子能量范围为1.7 eV ~ 6.0 eV的尺寸选择支撑团簇进行光谱研究，以研究尺寸选择的金属和半导体团簇支撑在氧化物表面的电子结构和光学性质。氧化物是理想的支撑材料，因为团簇的重要光学跃迁存在于它们的带隙中。在这些研究中，EW-CRDS，一种超灵敏的表面光谱学，将被开发和优化，用于在特高压条件下和低温下研究尺寸选择，支持簇。将考虑两种实验方案：a)单片折叠谐振器和b)微型立方体光学谐振器。在这两种情况下，团簇将沉积在两个光学器件的全内反射平面上，并将通过吸附相关的倏逝波用CRD进行光谱探测。两个空腔都具有与极化无关的精细度，允许研究与极化相关的现象。该实验方案将在该计划的第一个学期中用于研究沉积的单一尺寸金属团簇的光学吸收，以研究这些铸币金属团簇的电子结构差异，并通过分析偏振依赖吸收来获得其形态和结构的信息。这些团簇要么直接沉积在光学器件的SiO2表面上，要么沉积在生长在谐振器的非晶二氧化硅表面上的MgO和TiO2薄膜上。

This project aims at the spectroscopic study of size-selected, supported clusters in the photon energy range from 1.7 eV to 6.0 eV by means of the evanescent wave cavity ring-down spectroscopy in order to study the electronic structure and optical properties of size-selected metal and semiconductor clusters supported on oxide surfaces. Oxides are ideal support materials as important optical transitions of clusters lie energetically within their band gaps. For these studies the EW-CRDS, an ultrasensitive surface spectroscopy, will be developed and optimized for studying size-selected, supported clusters under UHV conditions and at cryogenic temperatures. Two experimental schemes will be considered: a) monolithic folded resonators and b) miniature cubical optical resonators. In both cases the clusters will be deposited onto the planes of total internal reflection of the two optical devices and will be probed spectroscopically by CRD through adsorption of the associated evanescent waves. Both cavities have a polarization-independent finesse, allowing polarization-dependent phenomena to be studied. This experimental scheme will be used in the first term of this program to study optical absorptions of deposited, metal clusters of a single size in order to investigate differences in the electronic structure of these coinage metal clusters and to obtain information of their morphology and structure by analyzing polarization-dependent absorptions. The clusters will either be deposited directly onto the SiO2 surface of the optical devices or onto thin MgO and TiO2 films grown onto the amorphous silica surface of the resonators.