Abstract
In a recent paper [Phys. Rev. A 37, 1087 (1988)] Gorceix and Indelicato study the difference between the multiconfiguration Dirac-Fock (MCDF) expectation value of the Lorentz and Coulomb gauge forms for the Breit interaction. After a slight rearrangement of their expressions, we have found that the difference can be written as a commutator with the full Hamiltonian. This commutator is nonvanishing due to projection operators onto positive energy states implicit in the MCDF approach and gives contributions O(). It is shown that the diagram involving the excitation of a single virtual electron-positron pair, which removes the discrepancy if the low-frequency limit is used also where it is not valid, does not do so for the proper frequency-dependent form and that a more detailed analysis is required.
- Received 28 September 1988
DOI:https://doi.org/10.1103/PhysRevA.39.3794
©1989 American Physical Society