Reaction geometry from orbital alignment dependence of ion pair production in crossed-beam Ba(1P1)–Br2 reactions

Strong orbital alignment dependence was observed for Ba+ produced in crossed-beam reaction of Ba(1P1) with Br2. The peak of this dependence varied strongly with scattering angle for alignment of the p orbital in the scattering plane, with the maximum flux seen for perpendicular alignment with respect to the relative velocity vector. The measured Ba+ was always favored by alignment of the orbital in the scattering plane, regardless of laboratory scattering angle. The experimental results suggest that this charge-transfer process is dominated by large impact-parameter collisions which achieve collinear nuclear geometry and Σ orbital alignment at the crossing point. Orbital locking is probably not important owing to the large internuclear distance of the crossing region.