ISOTHERMAL DESORPTION OF O-2 FROM AG(001)

The relevant parameters which characterise molecular desorption of O-2 -Ag(001) have been determined under isothermal conditions in the low c overage limit, using the beam-Bag method. We find a desorption order n =1.07+/-0.10, a desorption energy E-des=0.50+/-0.12 eV and a pre-expon ential factor v(des)1013.3+/-3.5 S-1. Such values compare well with th e thermal desorption parameters present in literature for molecular ox ygen adsorbed on Ag(110). The much lower dissociative adsorption proba bility of O-2 on Ag(001) is therefore due to the existence of a differ ent dissociation mechanism and not to a difference in the desorption p robability compared with Ag(110).