Product vibrational and rotational state distributions from the surface reaction F(ad)+H2(ad) → HF(g) (v′, J′)+H(ad/g)

Abstract

Product vibrational and rotational state distributions, ks(v′, J′), have been measured for the reaction F(ad)+H2(ad) → HF(g)+H(ad/g) in which both reagents are adsorbed on a 20 K surface consisting of polycrystalline CF4. The relative rate constants into vibrational levels v′=1 and v′=2, summed over the rotational levels, are [ks (v′=2)/ks (v′=1)]=0.58. The surface reaction therefore exhibits less vibrational excitation in the products than does the same reaction in the gas. Rotational excitation within each vibrational level is, however, comparable to that for the gas phase reaction. The product vibrational and rotational state distributions for surface reaction are markedly non-Boltzmann. Both the vibrational and the rotational excitation in the product of the surface reaction greatly exceed the equilibrium value for the surface temperature; ks (v′=2)/ks (v′=1) corresponds to a vibrational population ratio for 10 000 K, though TS=20 K.