Knowledge Bank

Electronic spectra are observed for the heteronuclear metal dimers CuLi and AgLi, with resonant one-color two-photon ionization (R2PI). The dimers are produced in a pulsed supersonic molecular beam by laser vaporization of either a copper or silver rod coated with a thin, vacuum deposited lithium metal layer. A total of twelve excited electronic states for CuLi and seven for AgLi are observed. Analysis of the vibrational progressions yields ground and excited state frequencies, anharmonicities and dissociation energies for both CuLi and AgLi. In addition, selected vibronic bands are rotationally resolved, giving bond lengths for CuLi and AgLi ($r3\prime \prime =1.73$ and 2.08 \AA respectively). The bond lenghts for CuLi and AgLi are significantly shorter than those in the homonuclear diatomics $Li2$ and $Cu2$ or $Ag2$. Dissociation energies in the heteronuclear dimers are also much greater than the mean of the corresponding homonuclear dimer values. These trends indicate that ionic bonding plays a leading role in the ground state bonding.