Multiconfigurational second-order perturbation study of the photochemical decomposition of methyl thionitrite

► The photodissociation of methyl thionitrite has been computationally studied by means of CAS-SCF and MS-CASPT2 methods. ► The low-lying excited potential energy surfaces of methyl thionitrite are repulsive with respect to NO, nitric oxide, elimination. ► The primary process after light absorption is NO, nitric oxide, extrusion.