Experimental study of the b3Π1ub3Π1u and 23Π1g23Π1g states of 85Rb285Rb2

Twelve ro-vibrational energy levels of the 85Rb285Rb2b3Π1ub3Π1u state have been observed using the Perturbation Facilitated Infrared-Infrared Double Resonance (PFIIDR) technique for the first time.Using the new observed levels as intermediate window levels, dozens of transitions into the 85Rb285Rb223Π1g23Π1g upper state ro-vibrational levels have been recorded.Compared with the experimental data of the 85Rb285Rb223Π0g23Π0g state, the average term value difference between the observed Ω=1Ω=1 and Ω=0Ω=0 components of the 85Rb285Rb223Πg23Πg state levels with the same rotational quantum number, is approximately 83.1±0.3cm-1. This proves that the 23Πg23Πg state has a spin-orbit splitting of 83.1±0.3cm-1, which shows that the 23Πg23Πg state tends to belong to Hund’s case (a).