The importance of this work has been attached to three spectroscopic systems of oxygen, namely, the electric dipole-forbidden transitions Herzberg Herzberg and Herzberg which are in close relationship with atmospheric science. An excitation mechanism, which is based on ab init io potential energy curves, spin-orbit couplings, and orbit-rotation couplings is put forward in the presented work. The computed results are contrasted with previous experimental results for integrated line cross-sections of the Herzberg bands, for J up to 20. It is found that the intensity properties of these three Herzberg bands are quite different. Then, the origin of the intensity in each Herzberg system has been analyzed and elaborated.