Ab initio MRD-CI study of excited states of formyl chloride HClCO and photofragmentation along Cl-C cleavage

Large-scale multi-reference configuration interaction (MRD-CI) calculations are carried out for ground and excited states of formyl chloride HClCO to investigate photofragmentation processes relevant to atmospheric chemistry. Four transitions at 6.89 eV (21A′), 8.06 eV (31A′), 8.51 eV (41A′) and 8.80 eV (51A′) are computed with considerable oscillator strengths. The strongest transition (51A′) corresponds with both σ → σ∗ (C-Cl) and π → π∗ (CO). The states 31A′ and 41A′ correspond to σ → σ∗ (C-Cl). The three lowest singlet 1A′ and 1A″ states are found to be repulsive upon elongation of the Cl-C bond.