Existence and Construction of Resonances for Atoms Coupled to the Quantized Radiation Field

For a nonrelativistic atom, which is minimally coupled to the quantized radiation field, resonances emerging from excited atomic eigenstates are constructed by an iteration scheme inspired by \cite{Pizzo2003} and \cite{BachFrohlichPizzo2006}. This scheme successively removes an infrared cut off in momentum space and yields a convergent algorithm enabling us to calculate the resonance eigenvalues and eigenstates, to arbitrary order in the feinstructure constant $\alpha \sim 1/137$, and is thus an alternative method of proof of a similar result obtained in \cite{Sigal2010}.