Electron energy loss spectroscopy studies of nitrogen adsorption on W(100)

Vibrational excitations of nitrogen on W(100) are investigated over the 100–300 K temperature range using elastic and inelastic electron scattering. New vibrational modes of nitrogen are identified that require different mode assignments from previous work. Experimental evidence for a molecular precursor to the atomic β₂ phase of adsorbed nitrogen is presented. Coverage dependent studies of vibrational modes suggests conversion between two different molecular surface phases and between atomic and molecular phases. A new ordered nitrogen phase characterized by a (4 × 1) LEED pattern is observed. The new phase appears to consist of orthogonal domains of p(4 × 1) symmetry that contain atomic nitrogen at the four fold sites (the β₂ atomic phase) with additional bridge-bonded nitrogen atoms in the unit cell.