ENERGY-TRANSFER, COLLISIONAL QUENCHING AND NATURAL LIFETIME OF LASER-EXCITED D1-PI STATE OF THE NARB MOLECULE

NaRb molecules in a thermal cell in a mixture of Na-Rb were excited to the D1-PI state by means of a 514.5 nm beam from an Ar+ laser. The natural lifetime for the NaRb D1-PI, upsilon' = 0, J' = 44 state, populated by the selective laser excitation, was found to be tau = 22.6 +/- 1.8 ns. The kinetics of the molecular fluorescence lines as a function of the Rb atom concentration were also studied. The rate constant for collisional quenching of this molecular level by Rb atoms could be determined to k(q) = 2.1 . 10(-9) cm3 s-1. The experiments at steady state conditions demonstrate that energy transfer to the atomic 4(2)D levels of Rb dominates the collisional quenching with a rate constant of k(ET) = 1.2 . 10(-9) cm3 s-1. The results suggest that such molecule-atom transfer of electronic energy can be used to efficiently populate 2D levels of alkali metal atoms.