500 nm System of RbCs: Assignments and Intensity Anomalies

Abstract

We have investigated the RbCs 500 nm system by mass-resolved resonance enhanced two-photon ionization in a cold molecular beam. The 4 (3)Pi(0) v' = 10-39, 4 (3)Pi(1) v' = 14-28, and 6 (1)Sigma(+) v' = 12-28 <- X (1)Sigma(+) v '' = 0 transitions have been observed and assigned for the first time. The 4 (3)Pi(0) v' <- X (1)Sigma(+) v '' = 0 transitions abnormally show double maxima of the vibronic-band intensity distribution around v' = 22 and 38. The intensities of the transitions to the lower vibrational levels (4 (3)Pi(0) v' = 10-32) are explained well by the direct transitions from the X (1)Sigma(+) v '' = 0 level following the Franck-Condon principle. The transitions to the higher vibrational levels (4 (3)Pi(0) v' >= 33) borrow intensities through the interaction with nearby 6 (1)Sigma(+) perturber levels.