Fine-structure transitions in Rb(5P) induced by H2and N2molecules

Abstract

The energy dependence and the absolute value of the cross section for the P1/2 to P3/2 fine-structure transition (FST) in Rb(5P) induced by H2 or N2 molecules and He atoms has been measured for the first time in a crossed-beam apparatus. The results for He, in excellent agreement with previous experimental data, are used for comparing atomic and molecular target behaviour with regard to FST processes in heavy alkalis. One observes much larger cross sections for H2 and N2 at low energies with a much weaker energy dependence. Theoretical work suggests two seemingly competing mechanisms for including large FST cross sections for molecular targets. One, involving an intermediate ionic complex, accounts for the general trend (absolute value and energy dependence) of the experimental data for N2 while the other, recently suggested by Hickman seems to play the major role when H2 is the target.