Spin-orbit effects in chemical reactions: The reaction of spin-orbit state-selected Ca(3P J) with Cl2, Br2, and CH3Cl

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Abstract
An optical pumping state selection technique is employed to investigate the effect of atomic spin‐orbit state on chemical reactivity for the Ca(3P0) level, for which the spin‐orbit splitting is small. The spin‐orbit dependence of the chemiluminescence and chemi‐ionization cross sections has been determined for the reactions of Ca(3P0) with Cl2, Br2, and CH3Cl. For the CaCl A–X and B–X chemiluminescence channels of the Cl2 and Br2 reactions, the spin‐orbit dependence is substantial, and the order of reactivity is J=2>J=1>J=0. The differences in reactivity of the spin‐orbit states for these channels in the CH3Cl reaction are much smaller, as is true also for the chemi‐ionization channels of all three reactions. No significant differences in reactivity were found for the C–X chemiluminescence channel in the Cl2 and Br2 reactions. The nonreactive intramultiplet mixing cross sections were estimated by modeling the dependence of the Ca(3P0→1S) emission intensity vs scattering pressure. These experimental results are interpreted in terms of the expected dynamics of these reactions. The spin‐orbit selectivity is related to how the asymptotic spin‐orbit states evolve into the different electrostatic covalent surfaces at smaller separations.