A THEORETICAL INVESTIGATION OF THE PROPARGYL RADICAL AND ITS CATION

Large-scale ab initio calculations have been carried out for the propargyl radical (H2C3H) and its cation. Both have rather similar planar equilibrium geometries so that the first band of the photoelectron spectrum is expected to show little structure. Our calculations confirm the assignment of matrix absorptions at 686.5 and 483.5 cm(-1) to the CH2 wagging and out-of-plane CCH bending vibrations, respectively. A strong band at 621 cm(-1) is predicted for the in-plane CCH bending vibration. The equilibrium dipole moment of H2C3H is calculated to be small; we recommend \mu(e)\ = 0.14 D. The calculated adiabatic ionization potential of 8.65 eV is in excellent agreement with the recent experimental value of 8.67+/-0.02 eV.