THE ADSORPTION CHARACTER AND DESORPTION-KINETICS OF THE WEAKLY-BOUND OXYGEN ON THIN IRON, PALLADIUM AND TITANIUM FILM SURFACES

New data concerning the electrical nature of adsorption as well as the kinetics of desorption of weakly bound oxygen state on thin metal fil ms, obtained in situ under controlled UHV conditions, are presented. T he measurements of surface potential (SP) have been carried out to dis tinguish between elementary steps of surface processes, accompanying t he formation of weakly bound oxygen states on thin Fe, Pd and Ti films at 78 and 298 K. These states appear under the oxygen pressure higher than 10(-4) Torr, following a strong chemisorption of oxygen adatoms. Both adsorption and desorption phenomena have been carried out under isothermal conditions. It has been found that weakly bound (activation energy of desorption < 18 kJ/mol), positively polarized oxygen admole cules (delta(+)), are present on Fe, Pd and Ti surfaces at 78 K, cover ing more than 65% of the monolayer located on the top of strongly chem isorbed oxygen adatoms. Weakly bound oxygen admolecules were also obse rved at 298 K oil thin Ti and Fe films (activation energy of desorptio n was in the range 80-95 kJ/mol). These admolecules are located on tie top of strongly preadsorbed oxygen adatoms, forming low-coverage (the ta approximate to 0.25), negatively polarized oxygen state (alpha(-)). The electrical nature of O-2 ordering in the weakly bound oxygen laye r at both temperatures has also been considered.