Cluster effects in O3/H2O photochemistry: Dynamics of the O+H2O→2OH reaction photoinitiated in the O3⋅H2O dimer

The dynamics of the 266 nm photoinitiated reaction of 16O3 and H218O were studied using 16O3⋅H218O van der Waals dimers to orient the initial reagents. In the absence of perturbations, the geometry of the 16O3⋅H218O dimer is such that 266 nm photolysis of cluster‐bound ozone initiates glancing O+H2O trajectories, with a 3 A impact parameter. Laser induced fluorescence probes show that 81±7% (2σ) of the ‘‘new’’‐16OH and essentially all of the ‘‘old’’‐18OH products were formed with v=0, with a slight preference for the Π(A’) Λ doublets, and average rotational energies of 900±130 and 760±80 cm−1, respectively. Approximately 19% of the ‘‘new’’‐16OH products form with v=1 and average rotational energy of 930±210 cm−1. No significant OH scattering anisotropy or other vector correlations were observed. Sub‐Doppler resolution experiments showed average kinetic energies for new‐16OH(v=0) products about 19% higher than for old‐18OH(v=0) products in the same rotational levels; increasing from values of about 500 cm−...