Cross sections for the collisions of metastable Mg*(3P) and Ca*(3P,1D) atoms with HX molecules (X = F, Cl, Br, I)

Collisions of the metastable Mg*(3P) and Ca*(3P, 1D) atoms with HF, HCl, HBr, and HI molecules have been studied in a beam-gas arrangement. The total collision cross section were determined from the attenuation of spectral lines emitted by the metastables and when possible from the dependence of chemiluminescence intensity on target gas pressure. The total cross sections for Mg*, Ca* + HC1, HBr, and HI are rather large and indicate harpooning mechanism. The Mg* reactions with HX give no electronic chemiluminescence while the Ca* +HX reactions produce electronically excited CaX* radicals for all HX targets studied. For the latter reactions electronic chemiluminescence cross sections and photon yields were determined.