Ab initio molecular orbital study of excited electronic states of the vinyl radical

Eight excited doublet electronic states of C2H3 have been studied using multireference configuration interaction calculations. Close agreement of the excitation energies with experiment is found for the Ã2A″, 52A′ (σ-n), and 32A″ (π-R) states where the experimental data are available. The undiscovered B 2 2A″ (n - π∗) state is predicted to have the adiabatic and vertical excitation energies of 33530 and 38546 cm−1, respectively. The π-π∗ C 2 2A′ state with the vertical energy of 45001 cm−1 is predicted to be difficult to observe because of the small oscillator strength.