Study of photodesorption dynamics by using pulsive synchrotron radiation

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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.