THE STRUCTURE-SENSITIVE ADSORPTION OF N(2) ON THE (1X1) AND (5X1) SURFACES OF IR(100)

The adsorption of N2 on the (1 x 1) and (5 x 1) surfaces of Ir{100} at 90 K has been studied using infrared reflection-absorption spectroscopy (IRAS), thermal desorption and LEED. On the (1 x 1) surface three distinct absorption bands are observed sequentially between 2211 and 2182 cm-1 as a function of exposure. On the (5 x 1) surface, under similar dosing conditions, only a broad weak feature is observed at approximately 2200 cm-1 due to adsorption at defect sites; only at pressures greater than 10(-7) mbar is N2 observed on the defect-free regions of the surface. Although the heat of adsorption is evidently lower, a similar sequence of absorption bands is seen as for the (1 x 1) surface.