J. Phys. Colloques
Volume 50, Numéro C8, Novembre 198936th International Field Emission Symposium
|Page(s)||C8-153 - C8-158|
J. Phys. Colloques 50 (1989) C8-153-C8-158
PHOTON INDUCED FIELD DESORPTION OF WATER CLUSTERSJ. DIRKS, W. DRACHSEL et J.H. BLOCK
Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, D-1000 Berlin 33, F.R.G.
Synchrotron radiation is used to study the photon induced field desorption from a water covered field emitter. Above a threshold photon energy of 7.1 eV, the desorption of a variety of water clusters (H2O)nH+, n=1, ..., 15 is observed. This threshold energy, which corresponds with the optical absorption maximum of liquid water, is found to be independent of cluster size and substrate material. The abundance of clusters decrease roughly exponentially with increasing cluster size and depends also on substrate temperature and photon energy. The analysis of the cluster distribution reveals an energy increment of 9 meV per water molecule which seems to be correlated to the frustrated translation energy of water molecules on metals. Basic RRK-theory arguments can be applied to explain the cluster distribution.