The ion-pair character of the B0+ state of CuAg

Abstract In order to obtain fundamental insight into the bonding properties of transition metals, the ( v ′ ,0) B-X transitions ( v ′ = 0 - 2 ) of the heteronuclear CuAg dimer are re-investigated by applying non-linear four-wave mixing and laser-induced fluorescence spectroscopy. The CuAg molecules in a molecular beam are produced by laser ablation of a Cu/Ag alloy target. Rotationally resolved spectra of the B-X transition are recorded. The measurements yield accurate molecular constants for four isotopologues and an equilibrium distance r e = 2.4577 ± 0.0003 A  for the B state. In particular, the B state is identified as an Ω = 0 + ion-pair state. The results corroborate the important contribution of the charge-transfer state to the metal-metal bond. The results are in good agreement with the recent calculations at the MRCI level of theory (Alizadeh et al., The Journal of Chemical Physics 141, 154301 (2014)).