Electronic Energy Partitioning in the Reactions of Metastable Mg*(3PJ) Atoms with F2, Cl2, Br2, I2, ICl, IBr

Abstract

Abstract Chemiluminescent reactions of metastable Mg*(3PJ) atoms with F2 , Cl2 , Br2 , I2 , IC1, IBr molecules were studied in a beam-gas experiment. For all homonuclear targets the MgX(A 2Π -X 2Σ+) emission was observed, but for IC1 and IBr reactants the Mgl(A-X) emission was absent and only MgCl(A-X) or MgBr(A-X) spectra were found. In addition, for the I2 , IBr, IC1, Br2 reactions, broad pseudocontinua extend from above 400 nm into the infrared. These pseudocontinua are ten-tatively attributed to the Mgl, MgBr (B' 2Σ+ -X2Σ+) transition. The total attenuation cross sections, chemiluminescence cross sections and quantum yields were measured. The quantum yields are all below 5%. The results are analyzed using information theory. The low yields for the Mg* + F2 system are explained by a barrier in the entrance channel. For other reactions the low yields are most probably caused by predissociation of the MgX*(A 2Π) products