Collision Reactions of Electronically Excited Hydrogen Molecules

Abstract

Relative abundances of ions produced in collisions of metastable H₂, HD, and D₂ molecules with various ground‐state molecules (M, RH₂) are reported. It is found that, in addition to Penning ionization and fragmentation of the target ion, deuteron addition reactions D₂*+M→MD⁺+D, exchange reactions D₂*+RH₂→(RD₂⁺+H₂), (RHD⁺+HD), and addition reactions with exchange D₂*+RH₂→(RH₂D⁺+D), (RD₂H⁺+H) occur. In the case of acetylene, propyne, and the 1‐alkenes C₂H₄, C₂H₆, C₄H₈, C₆H₁₂, the reactions are explained in terms of an intermediate ion complex RH₂D₂⁺ which decomposes within 10⁻⁶ sec. In the case of NH₃ and H₂O only deuteron addition without exchange occurs. This is explained in terms of a stripping mechanism. From the occurance of deuteron addition reactions in collisions with O₂, H₂O, HCl, CO₂, and CO, a lower bound for the proton affinity of these molecules of PA ≧ 6.2 was derived.