High resolution laser spectroscopy of the Cs2 C 1Πu state: Perturbation and predissociation

Abstract

High resolution spectra of the C 1Πu(v′,J′)−X 1Σg+(v″,J″) transitions of the Cs2 molecule were measured by the technique of Doppler-free optical–optical double resonance polarization spectroscopy. A number of C 1Πu(v⩾13,J) levels were found to be strongly perturbed. Transitions to the perturbing levels were observed, and the energy shifts of e and f levels of the C 1Πu state were studied and identified as originating from perturbations between the C 1Πu and (2)3Π1u states. Molecular constants of the C 1Πu(v=7–18) and (2)3Π1u(v=v0–v0+6) levels were determined. Line splittings were observed for the transitions to the C 1Πu(v=13 and 14,Jf) levels which were identified as hyperfine splittings originating from additional interaction with the (2)3Σu+ state. Remarkable line broadenings were observed in the transitions to the C 1Πu(v>15,Je and f) levels, and were identified as originating from the predissociation through the dissociative (2)3Σu+ state. The repulsive potential curve of the (2)3Σu+ state was estimated to cross that of the C 1Πu state around the outer turning point of the C 1Πu(v=16 or 17) level.