Molecular beam chemiluminescence. IX

Two distinct chemiluminescence bands of the Sm+N2O reaction, presumably due to two electronic states of SmO*, have been studied as a function of collision energy and vibrational N2O temperature in a crossed beam experiment. The reaction cross section is enhanced particularly at low collision energies by vibrational excitation (presumably γ2 bending mode) of N2O. The averaged state-to-state cross sections sigma obtained from the excitation functions after removal of their statistical bias, are identical for both emitting states, with and without vibrational excitation of reactants. The threshold behaviour is dominated by barrier surmounting as described by a modified close collision model. Rate constants for chemiluminescence production and for Sm-beam attenuation (approximately total reaction) were measured in a beam-gas experiment. They yield Arrhenius plots with strong curvature of opposite sign. Relative quantum yields are obtained as a function of average reactant energy. (Auth.)