Thermal and Photodesorption from a Molecular Surface: Ammonia on Ag₂

The one-to-one complex Ag₂NH₃ was prepared by titrating disilver with ammonia. Its photodissociation along ground and excited state potential surfaces was studied. Binding energies and the ammonia umbrella frequency were determined to be in good accord with precise electronic structure calculations showing that the complex is linear. Complexes of this type are important members of a series that extend to infinite surfaces. They allow the dynamics of particular adsorbate excitations to be isolated. Here, an excitation at 3 eV involving the metal-metal and the chemisorption bond is revealed.