Journal of Physics B: Atomic and Molecular Physics
Theoretical results for spin-forbidden electric-dipole transitions have recently been questioned on the grounds that relativistic corrections to the transition operator were not included. It is shown here that these corrections are automatically included when the transition operator is expressed in the dipole length form. The above criticism of previous dipole-length calculations is therefore unfounded. The 1s2p 3P1-1s21S0 and 1s2p 3P1-1s2s 1S0 transitions of helium are discussed as specific numerical examples.
Drake, Gordon W. F.. (1976). Relativistic corrections to spin-forbidden electric-dipole transitions. Journal of Physics B: Atomic and Molecular Physics, 9 (7), L169-L171.