The Dissociaitve Ionization of C2H2 and C2D2. The [CH(CD)]+ dissociaiton channel. The H(D)C-C(D)H Binding Energy.

The dissociative electroionization of C2H2(C2D2) has been investigated in the CH+(CD+) dissociation channel. The translational energy distribution of the fragment ion has been examined as a function of the electron energy between 20 and 99 eV. The first differentiated ionization efficiency curve has been measured for KE(CH+)=0.0-6.0 eV. Threshold energies of CH+ and CD+ have been measured and the effect of isotopic substitution is discussed. For the lowest onset of both CH+ and CD+, and from the kinetic energy measurements, the C-C bond strength has been derived, i.e. D(HC-CH)=9.83+/-0.10 eV. Higher appearance energies are assigned and reaction mechanisms are proposed. Above 34 eV electron energy, the CH+ ions carrying 2.0-5.5 eV kinetic energy are produced through Coulomb explosion of (C2H2)2+ states.