The reactions of Na{sub 2} with O{sub 2}

The reactions of Na{sub 2} with O{sub 2} were studied in a crossed-beam experiment at collision energies (E{sub c}) of 8 and 23 kcal/mol. The formation of NaO{sub 2} + Na was observed at both collision energies, with the angular distributions of NaO{sub 2} in the center of mass coordinates peaking strongly forward with respect to the direction of the O{sub 2} beam, suggesting that the reaction is completed in a time scale that is shorter than one rotational period of the molecular system. From the velocity distribution of the products, the authors found that the newly formed NaO{sub 2} molecules are internally excited, with less than 20% of the available energy appearing in the translational motion of the separating products. These results indicate a ``spectator stripping`` mechanism for the reaction, with the O{sub 2} stripping one Na off the Na{sub 2} molecules. At E{sub c} = 23 kcal/mol the cross section for this reaction channel is estimated to be 0.8 {angstrom}{sup 2}. Another reaction channel which produces NaO + NaO was seen at E{sub c} = 23 kcal/mol. The angular distribution for NaO is broad and forward-backward symmetric in the center of mass frame. A substantial fraction of the available energy is released into the relative motion of the products. This reaction is likely to proceed on an excited potential energy surface since a charge transfer to the excited O{sub 2}{sup {minus}} orbitals seems necessary for breaking the O-O bond. The measurement yields a bond energy of 60 kcal/mol for the Na-O molecule, and a total cross section of 2 {angstrom}{sup 2} for this reaction channel at E{sub c} = 23 kcal/mol