Preexponential factors for hydrogen desorption from single crystal metal surfaces

Partition functions for adsorbed hydrogen atoms have been evaluated for Ni(100), Ni(111), Pd(111) and Pt(111) surfaces. These account for the relative order of magnituted of the preexponential factors for associative desorption, ν_d, including the abnormally low value for the Pt(111)/H system. Furthermore application of transition state theory yields numbers for ν_d which are in good agreement with experimental data.