Absolute Dissociative Electron Attachment Cross Sections in Acetylene and its Deuterated Analogue

An instrument for the measurement of absolute dissociative electron attachment cross sections was constructed and applied to two prototype molecules, acetylene (C2H2) and deuterated acetylene (C2D2). The isotope effect at the first dissociative electron attachment band at 3 eV was determined–the cross section for C2D?/C2D2 is 14.4 times smaller than that for C2H?/C2H2. The results play a central role in validating recent theoretical work of Chourou and Orel. The dominant fragments at the second dissociative attachment band around 8 eV are the light fragments H? or D?. These bands exhibit weaker isotope effects