Inverse photoemission studies of the (100) surface of tungsten: Clean and with adsorbed submonolayers of hydrogen

The W(100) surface has been studied using k-resolved inverse photoelectron spectroscopy. Several peaks associated with unoccupied states were discovered. The energies of these peaks were mapped along the Γ̄M̄ line of the surface Brillouin zone. Exposure of the tungsten surface to small amounts of residual hydrogen caused the tungsten surface to reconstruct to its c(2×2)–H structure and drastically changed the band structure which has also been mapped. The obtained experimental results confirm the theoretical notion that the energy driving this reconstruction originates from the splitting of a partially occupied surface-state band into occupied bonding and unoccupied antibonding subbands.