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 ar
e described. The binding energies of NH3 on Cu-2 and Ag-2 have been de
termined, and spectroscopic data and theoretical results have been use
d to infer a quasi-linear or end-on coordination geometry for the comp
lexes. A simple picture of the bonding mechanism is presented, and com
parisons are made with ammonia adsorbed on copper and silver atoms and
bulk surfaces.