Spectroscopy and electronic structure of jet-cooled NiCu

Diatomic nickel-copper, NiCu, has been investigated by resonant two-photon ionization spectroscopy in a jet-cooled molecular beam. Six band systems have been identified over the range 11 500-16 500 cm-1. The ground state of NiCu has been determined to be X 2?5/2, with ?"e = 273.01 ? 1.15 cm-1, ?"exe" = 1.00 ? 0.38 cm-1, and r"e = 2.233 ? 0.006 ?. This state derives from a strongly bound (2.05 ? 0.10 eV) 3d10Cu3d9Ni4s?2 configuration. Excited states observed in this work derive from the more weakly bound 3d10Cu3d8Ni4s?24s?*1 configuration, and are characterized by smaller vibrational frequencies (191-208 cm-1) and a longer bond length (2.351 ? 0.005 ?) than the ground X2?5/2 state.