Observation of the 41Σg+ State of Rb2

Abstract Using Infrared-Infrared Double Resonance (IIDR) high resolution spectroscopy, we have observed the 20 200–21 600 cm −1 energy range of the 4 1 Σ g + electronic state of Rb 2 . The absolute vibrational quantum number assignment is based on the isotope effect using 824 rovibrational levels assigned to the 85 Rb 85 Rb and 85 Rb 87 Rb isotopomers. In addition to perturbations between the 4 1 Σ g + and 3 1 Σ g + state, strong couplings between the 4 1 Σ g + and 2 3 Π g states were observed. Preliminary molecular constants and an RKR potential energy curve are given.