SPECTROSCOPY OF JET-COOLED YCU

Optical spectra of jet-cooled diatomic YCu have been recorded using resonant two-photon ionization spectroscopy in a supersonic expansion of helium. The ground state is shown experimentally to be of 1∑+ symmetry, with a measured bond length of r″e = 2.6197(6) Å and a vibrational frequency of 193.21(24) cm-1 for 89Y63Cu. Five excited electronic states are identified as the [10.2]1∑+ state, the [11.8]3∏ 0+ state, the [12.0]3∏1 state, the [14.0]1∏ state, and, with the help of ab initio theory, the [12.2]1∏ state. No evidence whatever for participation of the 3d orbitals of copper in the chemical bonding is found, and the electronic structure of YCu is found to exhibit a striking similarity to that of YH. © 1995 American Institute of Physics.