Optical Spectroscopy of Diatomic Species: Copper with Group 14 Elements (Si, Ge, Sn, Pb)

Electronic band systems of the gaseous diatomic compounds of copper and various X elements of the 14th column (Si, Ge, Sn, Pb) have been observed by thermal excitation in the red part of the visible spectrum. Vibrational analysis of the two subsystems observed for each of these molecules (except for CuPb with only one system) are reported and assigned as 2Σ+–2Π3/2 and 2Σ+–2Π1/2 transitions. The variation of the spin–orbit splitting of the 2Π lower states from CuSi to CuSn follows closely that of the np shell spin–orbit parameters in the group 14 atoms. This fully corroborates previous ab initio calculations that predict a 2Πr ground state with the ionic Cu+ (3d10)X−(pς2pπ) configuration for these molecules.