Doppler-Resolved Laser Probing of Photon-Initiated Bimolecular Collisions O(1D) + CH4 → OH(v,N) + CH3

The stereodynamics of the reaction O(¹D) + CH₄ → OH(v ≤ 4,N) + CH₃ at collision energies of ? 40 kJ mol^?1, has been probed via Doppler-resolved, polarized laser-induced fluorescence spectroscopy. Velocity-aligned, reagent O(¹D) atoms were generated under bulb conditions via polarized laser photodissociation of N₂O. Analysis of the Doppler profiles of nascent OH(v,N) fragments has allowed both scalar and vectorial product correlations to be determined, including differential scattering cross sections and rotational alignments. These imply the operation of a ‘delayed’ collision mechanism, dominated by the deeply attractive potential energy surface associated with the insertion to form CH₃OH; the intermediacy of a long-lived complex is excluded, however. Rotational angular momentum in the recoiling OH fragments is preferentially aligned perpendicular to, and azimuthally distributed about, their recoil velocity. The rotational excitation is thereby attributed to bending motion in the C···O···H plane during the reagent collisions. The scalar product pair correlations establish a near-zero translational exoergicity and anticorrelated internal energy distributions in the two reaction products.