Optical–optical double resonance polarization spectroscopy of the B 1Π state of 39K85Rb

High resolution spectra of the B 1Π←X 1Σ+ transition of the 39K85Rb molecule have been measured with the technique of Doppler-free optical–optical double resonance polarization spectroscopy. Molecular constants of the B 1Π(v′=0−12) levels are determined, and the RKR potential is calculated. A number of irregularities in the energies of B 1Π state levels and intensity anomalies are observed. The energy shifts of the e and f levels of the B 1Π state are studied, and the perturbations between the B 1Π and 3Σ+ states and between the B 1Π and 3Π1 states are identified. Several transitions to the 3Π1 and 3Σ+ states are also observed, and the molecular constants of the 3Π1 and 3Σ+ states are evaluated. The single rovibrational level B 1Π(v′=2, J′=41) is selectively excited by a single frequency laser chopped by an electro-optical modulator, and the decay time of the resulting fluorescence is measured at various pressures. From the Stern–Volmer plot, the radiative lifetime and the collisional cross section of the fluorescence quenching are determined to be 11.6 ns and 29 Å2, respectively. The intensity distribution of the dispersed fluorescence of the B 1Π(v′=2, J′=41)→X 1Σ+(v″=0−11, J″=42) transitions is in very good agreement with the calculated values of ν4|〈v′=2|v″〉|2. The magnitude of the transition dipole moment is determined to be 9.2 D in the range of 4.08 Å