Collisions of electronically excited molecules: differential cross-sections for rotationally inelastic scattering of NO(A²Σ⁺) with Ar and He

Abstract

The paper reports experimental measurements and theoretical calculations of rotational-state-resolved differential scattering cross-sections (DCS) for collisions between electronically excited NO(A²Σ⁺) molecules and rare gas atoms. The experimental NO(A²Σ⁺) + Ar and NO(A²Σ⁺) + He state-resolved product scattering distributions are determined using velocity-mapped ion imaging. The ion images are analysed to determine the state-resolved DCS, which are compared with new theoretical DCS calculated using quantum scattering methods on ab initio electronic potential energy surfaces. Both collision systems are imaged simultaneously; this constraint on the collision energies of the two systems aids the comparison to theory. The experimental and calculated DCS agree well for the NO(A²Σ⁺)/He system. For the NO(A²Σ⁺)/Ar scattering system, the experiments do not recover the degree of forward-scattering theoretically predicted and significant differences in the positions of the observed and predicted rotational rainbow features are apparent at large scattering angles, particularly for the most rotationally inelastic collision channels investigated: ΔN = 12,14.

Acknowledgments

J.J.K., J.D.S., K.E.S. and D.W.C. acknowledge funding for this work provided by the Department of Energy, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences, and Biosciences. Sandia is a multi-program laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy under contract DE-AC04-94AL85000. J.K. and M.H.A. acknowledge support by the Chemical, Geosciences and Biosciences Division, Office of Basic Energy Sciences, Office of Science, US Department of Energy, under Grant No. DESC0002323. K.G.M. and M.L.C. would like to thank the EPSRC for a PhD studentship for G.P. The Edinburgh authors would also like to thank the school of Engineering and Physical Sciences at Heriot-Watt University for supporting M.L.C. and G.P. to visit Sandia.