Forbidden transitions such as intercombination ones, appear due to relativistic effects. In light atoms these effects are usually incorporated through the use of Breit-Pauli Hamiltonian. We show that for some transitions such as $E2\mathrm{}$ or $M1\mathrm{}$ this treatment is incomplete. There exist additional corrections to the transition amplitude which can be equally significant. We analyze also the role of the anomalous magnetic moment of the electron in some forbidden transitions.

• Received 22 October 2002

DOI:https://doi.org/10.1103/PhysRevA.67.012504