CLUSTER ISOLATED CHEMICAL-REACTIONS - REACTIVITY OF BA ATOMS AND SMALL BA CLUSTERS WITH SF6 AND CO2 MOLECULES ON LARGE ARGON CLUSTERS

The cluster isolated chemical reaction technique was used to investiga te the reactivity of the Ba/CO2 and Ba/SF6 systems in the environment of Ar-approximate to 6000 clusters. The method was extended to documen t several aspects of the reactivity. Notably, mass spectrometry gives insight into the full reactivity of the system deposited on the cluste rs. Laser induced fluorescence (LIF) and chemiluminescence are also us ed as detection tools. Unexpectedly, we found that a single barium ato m neither reacts with CO2 nor with SF6, at the cluster temperature (32 K). In contrast, the LIF results suggest the formation of a weakly bo und covalent Ba ... CO2 complex. Finally, Ba-2 and larger barium aggre gates react with CO2, and Ba-3 and larger aggregates react with SF6. T he chemiluminescent products are Ba2O in the first case, and BaF in th e second. These observations are rationalized on the ground of the har poon model. (C) 1997 American Institute of Physics.