Shape resonance of sulphur dioxide anion excited states using the CAP-CIP-FSMRCCSD method

We have studied the shape resonance of excited states of sulphur dioxide (SO₂) anion by using the correlated independent particle Fock space multi-reference coupled cluster (CAP-CIP-FSMRCCSD) method augmented by complex absorption potential. These resonant states have been trapped experimentally in recent years by electron collision. In particular, we have investigated e^–-SO₂ scattering and computed the negative-ion resonance states of the ${SO}_2^{-}$ anion responsible for the two resonances around 4.45 and 6.56 eV and compared the results with the existing experimental observations. From the computational results using the CAP-CIP-FSMRCCSD method, it has been observed that both the resonances near 4.45 and 6.56 eV result from A₁ symmetries.