Spectrosopic studies of jet-cooled NiAu and PtCu

Spectroscopic investigations of NiAu and PtCu have revealed that both molecules possess 2?5/2 ground electronic states, and are in this respect analogous to the isovalent molecule NiCu. The ground-state bond lengths (r?) have been measured as 2.351?0.001 ? and 2.335?0.001 ? for NiAu and PtCu, respectively. Ionization potentials have been bracketed as well, giving IP (NiAu) = 8.33 ? 0.38 eV and IP( PtCu) = 8.26 ? 0.07 eV. A reanalysis of previous high-temperature Knudsen effusion mass spectrometric data provides Doo( NiAu) = 2.52 ? 0.17 eV. The implications of these results for the electronic structure and chemical bonding of NiAu and PtCu are discussed, and comparison is made to the other diatomic metals of the nickel and copper groups.