Resonance Scattering of Electrons from ${\mathrm{N}}_2$, CO, ${\mathrm{O}}_2$, and ${\mathrm{H}}_2$ Adsorbed on a Silver Surface

Inelastic electron scattering from the vibrations of ${\mathrm{N}}_2$, CO, ${\mathrm{O}}_2$, and ${\mathrm{H}}_2$ adsorbed in monolayers and multiple layers on Ag films at $T\sim 20$ K show energy-dependent cross sections characteristic of resonance scattering via temporary negative-ion states. The resonances for these adsorbed phases generally occur at lower energies than in the gas phase and have spectral features which indicate negative-ion lifetimes of less than ${10}^{-14\mathrm{}}$ sec.