REACTIONS OF SODIUM CLUSTERS WITH WATER CLUSTERS

In a crossed molecular beam experiment, the reactive scattering of sod ium clusters Na-n (n less than or equal to 21) with water clusters (H2 O)(m) (m less than or equal to 40) is investigated. By measuring the a ngular and the velocity distributions of the scattered reaction produc ts, direct information on the reaction mechanisms is obtained. The sod ium clusters are generated in a supersonic expansion of sodium vapor f rom an oven with a refilling system with argon carrier gas. The produc ts are detected by photoionization at wavelengths of 308 and 355 nm an d mass analyzed in a time-of-flight mass spectrometer (TOF-MS), In add ition, a fast chopper with a pseudorandom sequence modulating the sodi um cluster beam allows us to determine at the same time the velocity d istributions of the products. The scattering of Na clusters with H2O c lusters shows only one series of reaction products, that is, solvated sodium atoms Na(H2O)(m) (m less than or equal to 32) with maximum inte nsities at m = 4, 5, 6. For all products, the measured angular and vel ocity distributions exhibit the formation of a complex that is stabili zed by isotropic evaporation of water molecules. The detected products have low translational energy. Products containing NaOH have not been observed.