Spin-orbit splitting in the ground X 2Π electronic state of the BAr van der Waals complex

The spin-orbit excited 2Π32 manifold of 11BAr(X2Π) was observed in a free jet supersonic expansion by laser fluorescence excitation in the B2Σ+ − X2Π (7,0) band. In previous work we observed transitions from the lower 2Π12 manifold. The spin-orbit constant A was determined to equal 10.88±0.08(1σ) cm−, close to a simple estimate, 23ΔE = 10.17 cm−, where ΔE is the boron 2p2P32−2P12 spin-orbit splitting. The near equality of experimental and theoretical values of A suggests that the boron 2p orbital is not strongly affected by the weak, nonbonding BAr interaction.