Study of photodesorption dynamics by using pulsive synchrotron radiation

本项目的目的是研究固体表面的光解吸动力学。研究结果如下：(1)利用同步辐射和准单色强波动辐射，在价能级和核能级激发对应的能级范围内观察到激发态碱原子的解吸现象。这意味着解吸是由价态激发和核能级激发引起的。(2)激发态碱原子与基态碱原子脱附强度的温度、辐照剂量和物质依赖性有很大差异。(3)利用脉冲同步辐射成功地观测了激发态碱原子的时间响应。时间响应由纳秒分量和微毫秒之间的慢分量组成，表明两种（快和慢）脱附机制。(4)从KCl和KBr中获得基态钾原子的激光诱导荧光信号。通过改变同步辐射与二极管激光器之间的时间，首次观察到基态碱脱吸的时间响应。任何现有的模型都不能解释基态碱原子的快速解吸。(5)光解吸实验与光电子能谱仪在同一实验室内进行，以了解吸附剂对固体表面的影响。

The purpose of the present project is to investigate photodesorption dynamics on solid state surfaces. The followings are the results of the present projects :(1) By using synchrotron radiation covering wide energy range and quasi-monochromatic intense undulator radiation, desorption of excited-state alkali atoms were observed in the energy ranges corresponding to the valence and core level excitations. This means that desorption is caused by valence excitation as well as core-level excitation.(2) Temperature, irradiation dose, and substance dependences of the desorption intensities were very different between excited-state alkali atoms and ground state alkali atoms.(3) Time response of the excited-state alkali atoms was successfully observed by using pulsive synchrotron radiation. The time response consisted of a nano-second component and a slow component between micro and milli-seconds, indicating two (fast and slow) desorption mechanisms.(4) Signal of the Laser-Induced-Fluorescence was obtained on ground state potassium atoms from KCl and KBr. By changing the timing between synchrotron radiation and a diode laser, the time response of the ground-state alkali desorption was observed for the first time in the world. Any existing model cannot explain the fast desorption of the ground-state alkali atoms.(5) Photodesorption experiments were carried out in the same chamber as the photoelectron spectrometer to know the effects of the adsorbates on the solid surfaces.