High-level ab initio studies of NO(X2Π)–O2(X3Σg−) van der Waals complexes in quartet states

Abstract

ABSTRACTGeometry optimisations were performed on nine different structures of NO(X2Π)–O2(X3Σg−) van der Waals complexes in their quartet states, using the explicitly correlated RCCSD(T)-F12b method with basis sets up to the cc-pVQZ-F12 level. For the most stable configurations, counterpoise-corrected optimisations as well as extrapolations to the complete basis set (CBS) were performed. The X structure in the 4A′ state was found to be most stable, with a CBS binding energy of −157 cm−1. The slipped tilted structures with N closer to O2 (Slipt-N), as well as the slipped parallel structure with O of NO closer to O2 (Slipp-O) in 4A″ states have binding energies of about −130 cm−1. C2v and linear complexes are less stable. According to calculated harmonic frequencies, the X isomer is bound. Isotropic hyperfine coupling constants of the complex are compared with those of the monomers.