In a high resolution laser excitation spectrum of NO 2, lines were recorded which do not follow the selection rule ∆ N = ∆ J = ∆ F of "spin allowed" transitions. Line positions and intensities of these "spin forbidden" lines were investigated for all rotational lines up to N″ = 12 of the Ka = 0 subband around λ = 592.5 nm. While the observed line intensities of "spin allowed" transitions can be well described by the J-coupling scheme, neither the J- nor the G-coupling scheme sufficiently describes the "spin forbidden" transitions. The observations can be fitted satisfactorily by perturbation theory, in which the Fermi interaction in 2A1 is treated as the perturber. This looks similar to a superposition of J and G scheme in the 2A1 ground state.