AN INVESTIGATION OF VIBRATIONALLY ASSISTED ADSORPTION - THE CASES H-2/CU(110) AND H-2/AL(110)

In the system H2/Cu(110) vibrationally assisted adsorption has been investigated by the use of seeded beams. Through a measurement of the internal energy contribution to adsorption at a constant translational kinetic energy of the hydrogen beam, the vibrational state of the adsorbed hydrogen can be determined. The seeded beam with excess vibrational energy adsorbs in the low translational kinetic energy range for H2 as nu = 1 whereas deuterium prefers the state nu = 2. To obtain similar adsorption rates for H2/Al as in the case of H2/Cu one needs about 0.2 eV additional translational kinetic energy. For the adsorption of hydrogen on aluminum no vibrational contribution can be detected within the margin of error.