title: Communication: Spectral representation of the Lamb shift for atomic and molecular calculations.
abstract: A spectral representation of the self-energy based on hydrogenic atomic data is examined for its usefulness to evaluate the self-energy of many-electron atoms, and thus its potential for molecular calculations. Use of the limited hydrogenic data with a diagonal projection overestimates the valence self-energy by an order of magnitude. The same diagonal projection for the vacuum polarization produces a similar overestimate, but a full projection produces values that are within a factor of 2 of the exact value, as does a density-fitting procedure.
authors.affiliation: Dirac Solutions, 10527 NW Lost Park Drive, Portland, Oregon 97229, USA. diracsolutions@gmail.com
authors.forename: Kenneth G
authors.initials: KG
authors.lastname: Dyall