Field-Ion Spectroscopy of Electronic States at Clean and Adsorbate-Covered Tungsten Surfaces

Measurements are reported of the kinetic energy distributions of field-ionized noble gases on both clean and nitrogen-adsorbate-covered surfaces of tungsten. The structure observed is attributed to the energy distribution of unoccupied electronic states at the metal surface. Correspondences are found with recent calculations of one-dimensional densities of states. A nitrogen-adsorption peak is observed at 0.6 eV above the Fermi energy.