SURFACE-DIFFUSION OF AG ON PD(100) MEASURED WITH SPECULAR HELIUM SCATTERING

We present a new method to determine surface diffusion constants using specular reflected thermal helium scattering. The specular reflected helium intensity is recorded in real time as a function of surface cov erage of the adsorbate and surface temperature. The experiment is comp ared to a model calculation based on rate equations for the generation and destruction of adatoms and clusters. We find E(dl) = 0.35 +/- 0.0 3 eV and nu(01) = 3 X 10(9) s(-1) as surface diffusion barrier and pre -exponential factor for the system Ag/Pd(100).