Chemiluminescence and rotational alignment in Mn*(a 4DJ, a 6DJ) + SO2 → MnO*(A′ 6Π, A 6Σ+) + SO

Measurements with 'hot' and 'cold' Mn atom beams, and analysis via the multiple line-of-centres procedure, have enabled the determination of separate state-to-state translational excitation functions for Mn*(a 4DJ, a 6DJ) + SO2 → MnO*(A′ 6Π, A 6Σ+) + SO. All indicate either a narrow cone of acceptance for reaction or a fairly flat angular dependence of the barrier, a result also inferred from ab initio density functional theory calculations on the lowest quartet surface. With increasing collision energy, the barrier appears to shift forward, suggesting a transition from 'soft-sphere' to 'hard-sphere' dynamics. For Mn*(a 4DJ) → MnO*(A 6Σ+) the rotational alignment -〈P2(ĵ′ · k̂)〉 at first falls with increasing collision energy, indicating preferred coplanar reaction geometry, but this preference is absent in all other channels. Simple molecular orbital-electron transfer arguments rationalise these observations and suggest strongly that Mn*(a 6DJ) reaction leads to SO*(a 1Δ) also.