Bethe' first calculated the Lamb shift for the hydrogen atom in 1947, using a method that was essentially nonrelativistic (NR), but nevertheless approximately correct. In 1948, Welton gave an intuitive derivation of the Bethe result by considering the coupling of the electron to second-quantized electromagnetic vacuum fluctuations —leading to the generally held folklore that vacuum fluctuations...

We give a general treatment of the spontaneous excitation rates and the non-relativistic Lamb shift of constantly accelerated multi-level atoms as a model for multi-level detectors. Using a covariant formulation of the dipole coupling between the atom and the electromagnetic field we show that new Raman-like transitions can be induced by the acceleration. Under certain conditions these transiti...

In an ensemble of identical atoms, cooperative effects like subor superradiance may alter the decay rates and the energy of specific transitions may be shifted from the single-atom value by the so-called collective Lamb shift. So far, one has considered these effects in ensembles of two-level systems only. In this work we show that in a system with atoms or nuclei under the action of an externa...