Neutralization of Intermediate Ions in the Radiolysis of Ethylene by Charge Exchange

The presence of nitric oxide and other additives of low ionization potentials during the radiolysis of ethylene markedly enhances the formation of butene‐1 and cis‐ and trans‐butene‐2. Yields of 1.4 to 1.6 molecule/100 eV absorbed in ethylene are reached at additive concentrations of 10% to 15%. The isotopic distribution of the butenes resulting from the radiolysis of ethylene—deuteroethylene—nitric oxide mixtures is typical of a molecular association mechanism, while the combined effects of electrostatic fields and nitric oxide demonstrate the absence of free radicals and excited species as precursors. The results suggest that intermediate butene ion produced by an ion—molecule association process of ethylene parent ion is relatively long lived and may be neutralized by charge exchange. This process apparently competes effectively with further ion—molecule reactions or unimolecular dissociation of [C₄H₈⁺]. The inference that G(C₂H₄⁺) $\text{≦1.5}$ ion/100 eV is in good agreement with the estimate G(C₂H₄⁺) = 1.5 based on mass‐spectrometric fragmentation patterns for 70‐eV electrons.