A new, fully ab initio investigation of the NO(X 2Π)Ar system.: I.: Potential energy surfaces and inelastic scattering

We report new coupled-cluster [CCSD(T)] ab initio calculations of the two potential energy surfaces (PES's) of the Ar-NO complex. Successively larger basis sets are used to extrapolate to the complete basis set limit. Although qualitatively very similar to our earlier PES's [M. H. Alexander, J. Chem. Phys. 99, 7725 (1993)], the new PES's have substantially deeper wells (D-e = 116 cm(-1)). Full close-coupled integral inelastic cross sections were determined at collision energies of 442 and 1774 cm-1 for transitions out of the lowest NO rotational level (j = omega = 1/2). For transitions into higher rotational levels of the same spin-orbit manifold the cross sections are little changed from previously calculated values, and still in some disagreement with recent experiments. For transitions in which the spin-orbit manifold changes (omega = 1/2 --> 3/2), the calculated integral cross sections are larger than the previously calculated values at E = 442 cm(-1) but agree quite closely at E = 1774 cm(-1). At both energies, however, the calculated cross sections for spin-orbit changing transitions are noticeably smaller than experimentally derived values. (C) 1999 American Institute of Physics. [S0021-9606(99)30138-0].