TRANSLATIONAL ENERGY THRESHOLDS OF THE MG(1S0) + N2O(X1-SIGMA+) -] MGO(X1-SIGMA+,A3-PI) + N2(X1-SIGMA-G+) REACTION

The reaction Mg(1S0) + N2O(X1-SIGMA+) --> MgO(X1-SIGMA+,a3-PI) + N2(X1-SIGMA-g+) has been studied with pulsed, crossed supersonic molecular beams, in the relative translational energy range epsilon-tr = 0.28-1.05 eV. The MgO(X1-SIGMA+,a3-PI) products have been detected by laser-induced fluorescence. Two translational energy thresholds have been found: the first threshold at 0.30 eV corresponds to the simultaneous appearance of MgO in the metastable state, a3-PI, and in the ground state, X1-SIGMA+, with a hot, inverted, vibrational distribution peaking at upsilon" = 3; the second one near 0.40 eV results in the growth of a cold MgO(X1-SIGMA+) vibrational distribution. These results are tentatively explained by crossings between the lowest singlet and triplet potential energy surfaces.