Decoherence in Excited Atoms by Low-Energy Scattering

We describe a new mechanism of decoherence in excited atoms that arise from particle scattering by the atomic nucleus. It is based on the idea that the scattering will produce a sudden displacement of the nucleus which will be perceived by the electron of the atom as an instant shift in the electrostatic potential. This will leave the atom’s wavefunction partially projected into lower-energy states which will lead to the decoherence of the atomic state. The decoherence is calculated to increase with the excitation of the atom, making observations of the effect easier in Rydberg atoms. We estimate the order of the decoherence for photons and massive particles scattering, analyzing several commonly presented scenarios. By maximizing the order of the effect it can be used for detection of weakly-interacting particles, like those which may be the constituents of Dark Matter, through applying very precise atomic spectroscopy.