Angular dependence of charge-transfer probabilities betweenO−and a Ni{100}-c(2×2)-O surface

The negative-ion fractions of oxygen directly recoiled from a Ni{100}-c(2 x2)-O surface have been measured as a function of both azimuthal and exit angles. The data show a pronounced angular dependence of the ion fractions. A theoretical analysis suggests that the probability for charge transfer between an oxygen atom and the surface varies strongly with lateral position. The experiments provide a 3D map of the local electron tunneling rates within the surface unit cell