Experimental study of the b3Π1u and 23Π1g states of 85Rb2

Abstract Twelve ro-vibrational energy levels of the 85 Rb 2 b 3 Π 1 u 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 85 Rb 2 2 3 Π 1 g upper state ro-vibrational levels have been recorded.Compared with the experimental data of the 85 Rb 2 2 3 Π 0 g state, the average term value difference between the observed Ω = 1 and Ω = 0 components of the 85 Rb 2 2 3 Π g state levels with the same rotational quantum number, is approximately 83.1 ± 0.3 cm - 1 . This proves that the 2 3 Π g state has a spin-orbit splitting of 83.1 ± 0.3 cm - 1 , which shows that the 2 3 Π g state tends to belong to Hund’s case (a).