Full-dimensional quantum dynamics of CO in collision with H2

Inelastic scattering computations are presented for collisions of vibrationally and rotationally excited CO with H-2 in full dimension. The computations utilize a newly developed six-dimensional potential energy surface (PES) and the previously reported four-dimensional V12 PES [P. Jankowski et al., J. Chem. Phys. 138, 084307 (2013)] and incorporate full angular-momentum coupling. At low collision energies, pure rotational excitation cross sections of CO by para-, ortho-, and normal-H-2 are calculated and convolved to compare with recent measurements. Good agreement with the measured data is shown except for j(1) = 0 -> 1 excitation of CO for very low-energy para-H-2 collisions. Rovibrational quenching results are presented for initially excited CO(v(1)j(1)) levels with v(1) = 1, j(1) = 1-5 and v(1) = 2, j(1) = 0 for collisions with para-H-2(v(2) = 0, j(2) = 0) and ortho-H-2(v(2) = 0, j(2) = 1) over the kinetic energy range 0.1-1000 cm(-1). The total quenching cross sections are found to have similar magnitudes, but increase (decrease) with j(1) for collision energies above similar to 300 cm(-1) (below similar to 10 cm(-1)). Only minor differences are found between para- and ortho-H-2 colliders for rovibrational and pure rotational transitions, except at very low collision energies. Likewise, pure rotational deexcitation of CO yields similar cross sections for the v(1) = 0 and v(1) = 1 vibrational levels, while rovibrational quenching from v(1) = 2, j(1) = 0 is a factor of similar to 5 larger than that from v(1) = 1, j(1) = 0. Details on the PES, computed at the CCSD(T)/aug-cc-pV5Z level, and fitted with an invariant polynomial method, are also presented. Published by AIP Publishing.