Ab initio MRD-CI study on the low-lying excited states of ClNO2

A theoretical study on the electronic absorption spectrum of nitryl chloride, ClNO2, has been carried out using multi-reference configuration interaction, MRD-CI, methods with cc-pVDZ + sp and cc-pVTZ + sp basis sets. The electronic spectrum is characterized by two very strong transitions (f from 0.30 to 0.67 ) at 7.04 eV (31A1←X1A1) and 7.25 eV (31B2←X1A1). Further, the transition at 5.77 eV (21A1←X1A1) is predicted to be somewhat less intense (f=0.02). In addition, the potential energy curves for the ground and low-lying singlet excited states are examined along the Cl–N bond cleavage. Also, triplet excited states of ClNO2 are discussed.