Ab initio molecular orbital calculations with large, polarization basis sets and incorporating valence electron correlation have been employed to examine the C2H2O]+˙ potential energy surface. Four C2H2O]+˙ isomers have been identified as potentially stable, observable ions. These are the experimentally well-known ketene radical cation, CH2?C?O]+˙ (a), and the presently unknown ethynol radical cation, CH2?C? OH]+˙ (b), the oxirene radical cation (c) and an ion resembling a complex of CO with CH2]+˙, (d). The calculated energies of b, c and d relative to a are 189, 257 and 259 kJ mol?1, respectively. Dissociation of ions a and d is found to occur without reverse activation energy.
