Low-energyHe+scattering from deuterium adsorbed on Pd(110)

We show that low-energy, helium ion scattering in the forward direction provides a surface specific means for directly observing adsorbed deuterium. Energy spectra of 1-keV ${}_{}{}^4{}_{}{}^{}\mathrm{He}_{}^{+}{}_{}{}^{}$ scattered at angles less than 30° from a surface with adsorbed D contain the two maxima predicted for classical single scattering. Angular studies indicate that D atoms adsorbed on the Pd(110) surface at room temperature reside in the troughs between atom rows.