SURFACE RECONSTRUCTION AND THERMAL-DESORPTION - O AG(110) - AN EXPERIMENTAL-STUDY/

We have studied the associative desorption of oxygen from well-defined O(nx1)-Ag(110) phases (n ranging from 8 to 2) by thermal desorption m ass spectrometry. Desorption peak profiles have been compared with cal culations based on a lattice-gas model [V.P. Zhdanov, Surf. Sci, 277 ( 1992) 155] which takes into account the missing-row reconstruction of the substrate and adsorbate-adsorbate interactions along independent - O-Ag-O- rows. The model works well at low coverage accurately reproduc ing the peak profiles. For the O(8 x 1),O(6 x 1) and O(4 x 1) phases, assuming a value of v = 10(15) s(-1) for the pre-factor, values of app roximate to 39 kcal/mol for the activation energy and approximate to - 2.5 kcal/mol for the O-O effective oxygen-oxygen interaction along -O- Ag-O- rows are obtained. At high coverage the assumption of independen ce of -O-Ag-O-chains is no longer valid and repulsive interactions per pendicularly to the chains have to be taken into account.