TEST OF B-SIGMA-INTERACTION POTENTIALS IN NA 3P-RARE GAS SYSTEMS FROM LIGHT-SCATTERING

The spectral dependences in Na-rare gas optical collisions Na 3S+X+hv --> Na 3P(J)+X have been used to study the long range interaction in Na 3P(J)-X systems. For a test of available potentials the fine structure (fs) population ratio and the J = 3/2 alignment were measure under single collision conditions by analyzing the fluorescence emitted after selective excitation of the molecular B-SIGMA or A-PI states as function of the laser frequency-nu. A comparison was made with quantum coupled channels (CC) calculations of thermally averaged spectral profiles using the potential data to be tested as input. In addition, model calculations were performed for a qualitative understanding of the role of the various nonadiabatic couplings involved and the trends in the spectral profiles by the corresponding molecular potentials. In NaAr and NaKr the B-SIGMA-fs wings are seen to depend sensitively on the parameters of the potentials, in particular on the well depth epsilon-SIGMA-PI of the B-SIGMA-A-PI difference potential which is comparable to the spin orbit interaction in these systems; the experimental profiles show, that the actual epsilon-SIGMA-PI values are much smaller than those predicted by the model potentials of Duren. In NaKr also the B-SIGMA-alignment wing depends sensitively on epsilon-SIGMA-PI caused by a long-range parity dependent rotational coupling, as follows from the CC-analysis. The comparison with the experimental alignment confirms the result from the B-SIGMA-fs wing regarding the actual epsilon-SIGMA-PI value.