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Auger-Electron-Probe Time-Resolved Surface XAFS Technique and Its Application to Study of Surface Dynamics

俄歇电子探针时间分辨表面XAFS技术及其在表面动力学研究中的应用

基本信息

批准号：
16072205
负责人：
KONDOH Hiroshi
金额：
$ 16.9万
依托单位：
The University of Tokyo
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research on Priority Areas
财政年份：
2004
资助国家：
日本
起止时间：
2004 至 2006
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-16072205/
关键词：
Time resolved XAFS XPS reaction dynamics reaction kinetics reaction mechanism 表面ダイナミクス

项目摘要

We have developed a fast surface x-ray absorption fine structure(XAFS)technique where solid substrates are irradiated by energy-dispersed synchrotron-radiation x rays and auger electrons emitted from x-ray absorbing surface species are collected at once with a spatially resolved way. In this project we aimed further development of this technique and its application to mechanistic studies on chemical reactions on solid substrates. The present improvement enabled us to trace changes in both surface and gas-phase species simultaneously every approximately 1 s. If this technique is applied to repeatable processes, we can detect submonolayer surface species with a time resolution of 10 ms by using a time gate for the detector. Furthermore we extended this technique to the undulator-based time-resolved x-ray photoelectron spectroscopy, which enabled us to observe dynamic processes of submonolayer surface species with a time resolution of 2 ms.Real-time monitoring of surface reaction kinetics based on these techniques provided following three major achievements in research that have never been achieved by previous methods.(1) Finding of a novel reaction pathway involving a NO dimer as a reaction intermediate under the reaction condition of NO reduction on Rh(2) Elucidation of cirrelation between phase transition of surface oxygen and reactivity under the reaction condition of CO oxidation on Pd(3) Detection of a transient high-density adsorption state with a life time of less than millisecond order induced by NO pulsed molecular beamThe present development of the fast observation technique for surface species and its application to surface dynamic processes open a way to study novel dynamic processes that have not been detected with previous static surface techniques.

我们开发了一种快速表面x射线吸收精细结构（XAFS）技术，该技术采用能量分散同步辐射x射线照射固体基底，并以空间分辨的方式立即收集x射线吸收表面物质发射的螺旋电子。在本项目中，我们旨在进一步发展该技术，并将其应用于固体基质上化学反应的机理研究。目前的改进使我们能够同时追踪表面和气相物质的变化，大约每隔1s。如果将该技术应用于可重复的过程，我们可以使用检测器的时间门以10 ms的时间分辨率检测亚单层表面物质。此外，我们将该技术扩展到基于波动器的时间分辨x射线光电子能谱，使我们能够以2毫秒的时间分辨率观察亚单层表面物质的动态过程。基于这些技术的表面反应动力学实时监测提供了以下三个主要的研究成果，这些成果是以前的方法从未实现的。(1)在Rh上NO还原反应条件下，发现了以NO二聚体为反应中间体的新反应途径(2)阐明了CO氧化Pd反应条件下表面氧的相变与反应活性之间的关系(3)NO脉冲分子束诱导的寿命小于毫秒级的瞬态高密度吸附态的检测它在表面动态过程中的应用为研究以前的静态表面技术无法检测到的新的动态过程开辟了一条道路。