J. Phys. Colloques
Volume 48, Numéro C6, Novembre 198734th International Field Emission Symposium / 34ème Symposium International d'Emission de Champ
|Page(s)||C6-227 - C6-232|
J. Phys. Colloques 48 (1987) C6-227-C6-232
PHOTON STIMULATED FIELD DESORPTION OF HYDROGEN FROM RHODIUMW. Drachsel1, S. Jaenicke1, A. Ciszewski2, J. Dösselmann1 et J.H. Block1
1 Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, D-1000 Berlin 33, F.R.G.
2 on leave from Institute of Experimental Physics, University of Wroclaw, PL-50 205 Wroclaw
Using synchrotron radiation (40-120 eV) from the BESSY storage ring, photon stimulated field desorption of hydrogen from a rhodium emitter was observed. The yield of photon-stimulated H2+ and H+, discriminated by a time-of-flight technique, displayed a strong photon energy dependence : a broad maximum at 70 eV was found ; the onset correlated with 4p3/2 and 4p1/2 core level excitations of rhodium, whereas the 4s-excitation caused no increase. The excitation transfer from the substrate to the adsorbate most probably takes place via metal Auger electrons (XESD-mechanism). From the temperature dependence of the desorption yield it is concluded that only field-adsorbed H2 can be desorbed following photon-excitation of the rhodium. The occurence of H+ as a desorbing species is attributed to field-dissociation and especially at high photon flux, also to photo-dissociation of H2+.