Ab initio calculations for the X 2Σ, A 2Pi, and B 2Σ states of NaAr: Emission spectra and cross sections for fine-structure transitions in Na--Ar collisions

Configuration interaction (CI) calculations were performed for the X 2Σ, A 2Pi, and B 2Σ states of NaAr. The A 2Pi state is calculated to have a well depth of 492 cm-1 at an internuclear separation of 3.04 A. Small wells of 55 and 32 cm-1 were found for the X 2Σ and B 2Σ states located at 5.01 and 6.80 A, respectively. The spectra for A 2Pi--X 2Σ emission in the limits of zero and infinite Ar pressure were calculated and compared with the experiment of York, Scheps, and Gallagher and the predictions using the pseudopotential curves of Pascale and Vandeplanque. The potentials from this work give spectra in much better agreement with experiment than the pseudopotential predictions. Total and differential cross sections for fine-structure changing transitions Na(2P/sub 1/2/) +Ar→Na(2P/sub 3/2/)+Ar-17.2 cm-1 were calculated by a quantum mechanical technique. The total cross sections are in excellent agreement with experimental results. The excited state differential cross sections exhibit prominent rainbow structure centered at tau/sub R/=ETHETA/sub R/=5.5--6.0 eV deg