Rotationally inelastic collisions between a molecule in a 2S+1Σ electronic state and an open-shell target: General quantum analysis and experimental measurement of state-resolved cross sections for CaCl(X 2Σ+)+NO(X 2Σ)

The general quantum treatment for the scattering of molecules in 2S+1∑ electronic states by open-shell 2S atoms is investigated, with particular emphasis given to the influence of the open-shell character of the atomic perturber on the collisional propensity for conservation of the e/f molecular symmetry index. The molecule-state-resolved cross sections are expressed as a sum of spin-independent and spin-correlated terms. The spin-independent term is formally equivalent to the cross section for state-resolved transitions in a 2S+1∑-state molecule upon collision with a structureless target. The spin-correlated term is due solely to the electrostatic exchange forces arising from the open-shell nature of both the molecule and the atomic target. Recently calculated CaCl(X 2∑+)–Ar cross sections are used to investigate the extent to which e/f conservation depends on the relative magnitudes of these two contributions. Experimental state-to-state rotationally inelastic cross sections for the scattering of CaCl(X 2∑+) by the open-shell NO(X 2∏) molecule are presented and analyzed by means of this formalism.