A theoretical derivation of closed form expressions for the intensities of all the rotational branches arising out of⁴Σ-⁴Π electronic transition in a diatomic molecule is described. In the present theory the tradition of treating the coupling in the⁴Σ state as belonging to Hund’s case (b) is discarded; instead a full-fledged intermediate coupling treatment which rigorously takes into account the spin-spin and second order spin-orbit effects is presented. Since accurate intermediate coupling treatment of⁴Π, in analytically closed form, is not possible, the⁴Π is first restricted to the extreme coupling scheme Hund’s case (a)(or case (b)); the effect of spin uncoupling (or spin-orbit and spin-spin interactions) is then incorporated through a first order perturbation calculation.