Oxygen chemisorption on metal surfaces: General trends for Cu, Ni and Ag

Molecular beam experiments on model catalysts

The energy released in low-energy chemisorption or physisorption of molecules on metal surfaces is usually expected to be dissipated by surface vibrations (phonons). Theoretical descriptions of competing electronic excitations are incomplete, and experimental observation of excited charge carriers has been difficult except at energies high enough to eject electrons from the surface. We observed reaction-induced electron excitations during gas interactions with polycrystalline silver for a variety of species with adsorption energies between 0.2 and 3.5 electron volts. The probability of exciting a detectable electron increases with increasing adsorption energy, and the measured time dependence of the electron current can be understood in terms of the strength and mechanism of adsorption.

https://science.sciencemag.org/content/sci/294/5551/2521.full.pdf

Chemically Induced Electronic Excitations at Metal Surfaces

Wide range nozzle beam adsorption data for the systems H2/nickel and H2/Pd(100)

We have investigated the dependence on the rotational and vibrational states of the translational energy of D2(v,J) formed in recombinative desorption from Cu(111). These results provide information about the effect of rotational energy relative to that of vibrational and translational energy on the dissociative chemisorption of D2 on Cu(111). The range of rovibrational states measured includes rotational states J=0–14 for vibrational state v=0, J=0–12 for v=1, and J=0–8 for v=2. D2 molecules were detected in a quantum‐state‐specific manner using three‐photon resonance‐enhanced multiphoton ionization (2+1 REMPI). Kinetic energies of desorbed molecules were obtained by measuring the flight time of D2+ ions in a field‐free region. The mean kinetic energies determined from these measurements depend strongly on the rotational and vibrational states. Analyzing these results using the principle of detailed balance confirms previous observations that vibrational energy is effective, though not as effective as tr...

Effect of rotation on the translational and vibrational energy dependence of the dissociative adsorption of D2 on Cu(111)

Differential trapping probabilities and desorption of physisorbed molecules: Application to NO/Ag(111)

Direct inelastic scattering of superthermal Ar, CO, NO and O2 from Ag(111)

Trapping-desorption of O 2 from Ag(111)

A well‐collimated supersonic beam of Ar or O2, optionally seeded in He, collides with a Ag(111) surface. The resulting momentum distribution of the scattered particles is measured using a rotatable quadrupole mass spectrometer and time‐of‐flight (TOF) techniques. Comparing O2 with Ar shows that O2 behaves in direct scattering from Ag(111) very much like the monoatomic Ar. Both Ar and O2 scattering can be described rather well by a hard‐cube model, although the parallel momentum is not conserved. The agreement between O2 and Ar suggests the existence of a potential barrier of at least 170 meV between the physisorbed and the chemisorbed O2 state on the Ag(111) surface.

M.E.M. Spruit

Papers

Differential trapping probabilities and desorption of physisorbed molecules: Application to NO/Ag(111)

Direct inelastic scattering of superthermal Ar, CO, NO and O2 from Ag(111)

Trapping-desorption of O 2 from Ag(111)

Molecular-beam scattering of O2 and Ar from Ag(111)

Angular and energy distributions of NO scattered from a Ag(111) surface