Spectroscopic studies of jet-cooled CuAg

Resonant two-photon ionization spectroscopy has been applied to jet-cooled diatomic CuAg. Four band systems have been observed, three of which have been rotationally resolved and analyzed. The ground state is X 1Σ+ in symmetry, deriving from the 3d10Cu4d10Agσ2 molecular configuration. Its bond length has been determined as r0=2.3735±0.0006 Å (1σ error limits). Based on an analysis of the possible separated atom limits, three of the excited states observed (A 0+, A′ 1, and B′ 0+ ) are assigned as primarily 3d9Cu4d10Agσ2σ* in character. The observation of unusually large electronic isotope shifts in the A–X, A′–X, and B′–X band systems, similar in magnitude to those previously observed in the A–X and B–X systems of Cu2 and the s←d excitations in atomic copper, provides further confirmation that these excited states derive from the 3d9Cu4d10Agσ2σ* molecular configuration. Finally, the highest energy state observed in this work is argued to be primarily ion pair in character, and is expected to have significant contributions from both the Cu+Ag− and Cu−Ag+ ion pair states.