Molecular beam study on BaO and SrO formation for clarifying interaction of metal-vapors with upper atmosphere oxygen

In crossed-beam experiments, reactive cross-sections for the oxidation of groundstate Ba and Sr atoms by oxygen molecules were determined over a wide range of relative collisional energies (0.1–1 eV). On the basis of rate constants, thus derived, it is shown that Ba oxidation in upper atmosphere releases proceeds predominantly via optically pumped metastable Ba states, whereas SrO concentrations will be too low to be seen, because an equilibrium unfavorable to oxide formation is established.