Finite-time deviations from exponential decay of dipole-moment expectation values in the case of spontaneous emission

Abstract

For the first time, to the authors' knowledge, a mathematically rigorous method is used for obtaining finite-time deviations from the exponential decay of the dipole-moment expectation values in the case of spontaneous Lyman-α transition in a two-level hydrogenic atom. In calculations counterrotating terms, yielding the frequency shift (Lamb shift) within the scope of the two-level model, are taken into account.