Hydrogen recombination on metals: vibrational excitation of desorbed molecules

The vibrational excitation of hydrogen molecules formed by recombination of hydrogen atoms on different metal surfaces has been studied. A recently developed experimental technique was used to determine vibrational state populations of the molecules up to v=7. Excitation of high vibrational levels is observed for molecules formed on metal surfaces which strongly chemisorb hydrogen. Metals with weaker chemisorption lead to vibrational excitation of lower levels, predominantly up to v=3. Knowledge of the vibrational state of desorbed molecules gives information on the energy of adsorbed hydrogen atoms and on the dynamics of surface reactions. This information is complementary to that obtained from studies of hydrogen reactions with metal clusters.