Quantum-state distributions for the HD product of the direct reaction of H(D)/Cu(111) with D(H) incident from the gas phase

We have determined the internal-state distribution for the HD product of the reaction of gas-phase D atoms with H atoms chemisorbed on Cu(111) and for the corresponding reaction of H atoms with chemisorbed D atoms. In the case of D-on-H, the populations of the vibrational states upsilon=0, 1, 2, and 3 are comparable, while that for upsilon=4 is considerably smaller, giving a mean vibrational energy of similar to 0.7 eV. The vibrational state distribution for H-on-D is similar, but in this case there is a clear peak at upsilon=1, even less population in upsilon=4, and a somewhat smaller mean vibrational energy of similar to 0.6 eV. The mean rotational energy falls with increasing upsilon in both cases, similar to 0.5 eV for upsilon=0 to <0.2 eV for upsilon=4, with an overall mean rotational energy of similar to 0.4 eV. The rotational distributions are distinctly narrower for H-on-D than for D-on-H. The maximum internal energy observed is similar to 2.3 eV, consistent with the total energy available to the product. Results are consistent with recent calculations. (C) 1996 American Institute of Physics.