State-resolved inelastic cross sections from CN A 2Π v=8 to X 2Σ+ v=12: Quenching of the even–odd alternation in the final rotational state populations

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Abstract
An optical–optical double resonance technique has been employed for the study of collisional transfer from the CN A 2Π v=8 manifold to X 2Σ+ v=12 with initial and final rotational state resolution. In contrast to our previous studies of vA=3 to vX=7 and vA=7 to vX=11 collisions, no significant even–odd oscillation in the final X state rotational populations was observed for any of the incident A state levels investigated. The absence of this alternation for vA=8 collisions is ascribed to the dependence on CN vibrational coordinate of the off-diagonal matrix element connecting the Σ and Π(A′) wave functions describing the CN(A,X)–Ar interaction. For all incident vA=8 levels studied, a preference for formation of X state e vs f levels of a given N was observed.