A molecular beam investigation of He, CO, and O2 scattering from Pd(111)

Abstract

Adsorption of CO and O₂ on Pd(111) has been studied with the molecular beam technique. Absolute sticking coefficients for CO and O₂ have been determined as a function of coverage, angle of incidence, and substrate temperature. Angular distributions of the scattered molecules show that the probability for capture in the precursor state is unity for CO at low coverages and for all substrate temperatures investigated and 0.5 for O₂ at low coverages independent of the substrate temperature. Modulated beam experiments show that E_des. for CO is 32 kcal/mole at low coverages. Phase sensitive detection and waveform analysis show that at high CO coverages on the impurity free surface and over a wide range of coverages on a carbon contaminated surface, three distinct CO species are present on the surface.