Photodissociation of Cu₂NH₃ and Ag₂NH₃^†

We report on the reactions of copper and silver dimers with ammonia in the gas phase near room temperature and on photodissociation of the 1:1 complexes. Photodissociation action spectra in the range 295−360 nm and emission spectra of metal dimers produced by photodissociation are described. The binding energies of NH₃ on Cu₂ and Ag₂ have been determined, and spectroscopic data and theoretical results have been used to infer a quasi-linear or end-on coordination geometry for the complexes. A simple picture of the bonding mechanism is presented, and comparisons are made with ammonia adsorbed on copper and silver atoms and bulk surfaces.