Spin-forbidden transitions in the vicinity of the 2 (1)Pi(u)<- X(1)Sigma(+)(g) band system of Rb(2)

Abstract

We have investigated the Rb(2) 475 nm system by resonance enhanced two-photon ionization spectroscopy in a pulsed molecular beam. Strong extra bands accompanying the 2 (1)Pi(u) nu' = 5 - 8 <- X (1)Sigma(+)(g) nu '' = 0 bands were newly observed. Rotational analysis of the main and extra bands reveals that the 2 (1)Pi(u) nu' = 5 - 8 levels are significantly perturbed, mainly by the 3 (3)Sigma(+)(u)(1(u)) state and also by the 2 (3)Pi(u)(1(u)) state. For the major perturber, 3 (3)Sigma(+)(u)(1(u)), the intensity borrowing has been found to be facilitated by the 2 (3)Pi(+)(u)(1(u)) potential energy curve crossing near 21100 cm(-1). For the vibronic-band intensities of the 2 (3)Pi(u)(1(u)) nu' <- X (1)Sigma(+)(g) nu '' = 0 transitions observed in this spectral region, intensity borrowing was most effective when the 2 (3)Pi(u)(1(u)) levels were close to the 3 (3)Sigma(+)(u)(1(u)) levels. A deperturbation fit for the perturbing bands has provided the 2 (1)Pi(u)-3 (3)Sigma(+)(u)(1(u)) coupling constants.