Observation and calculation of the Cs2 2Δ1g3 and bΠu3 states

The Cs2 2Δ1g3 and bΠ0u3 states have been observed by infrared-infrared double resonance spectroscopy for the first time. 221 2Δ1g3←AΣu+1←XΣg+1 double resonance lines have been assigned to transitions into the 2Δ1g3 v=6–13 vibrational levels. Resolved fluorescence into the bΠ0u3 v′=0–48 levels has been recorded. Molecular constants and potential energy curves are determined by the global fit of the entire set of the experimental data. Theoretical potential energy curves of the 2Δg3 and bΠu3 states have been determined in the framework of the pseudopotential method and are compared with the experimental results.