Potential energy surfaces for the interaction of CH( X  2Π, B  2Σ−) with Ar and an assignment of the stretch-bend levels of the ArCH( B ) van der Waals molecule

New multireference, configuration-interaction potential energy surfaces are reported for the interaction of Ar with the CH radical in its ground (X 2Π) and second excited (B 2Σ−) electronic states. These potential energy surfaces are then used in an adiabatic analysis of the rovibronic levels of the ArCH(X) and ArCH(B) van der Waals complexes. A qualitative discussion of the expected features in the B̃←X̃ electronic spectrum of ArCH is presented, and these are compared with the experimental spectrum reported earlier by Lemire et al. [J. Chem. Phys. 99, 91 (1993)].