The 3d?Ni(?F)3d10Cu???*? manifold of excited electronic states of NiCu

Diatomic NiCu has been supersonically cooled in a molecular beam and investigated by resonant two-photon ionization spectroscopy. A total of nine band systems connecting the ground 3d?Ni3??Cu??, X 2?5/2 state to the 3d?Ni(3F)3d??Cu??*?? manifold of states have been found, and bands of eight of these systems have been rotationally resolved and analyzed. Land S-uncoupling interactions have been found between two pairs of states, resulting in B[11.9]2.5 ~C[1.91]1.5 and [10.4]2.5~[10.4]1.5(?) heterogeneous perturbations. In the case of the B-C interaction, the magnitude of the perturbation matrix element has been deduced. The detailed spectroscopic analysis of the 3d?Ni(3F)3d??Cu??*?? manifold of states presented in this paper allows the electronic structure of NiCu to be understood in depth and provides a database for comparison to the ligand-field plus spin-orbit calculation of the NiCu excited states presented in the following paper.