Interference-assisted resonant detection of axions

Detection schemes for the quantum-chromodynamics axions and other axion-like particles in light-shining-through-a-wall (LSW) experiments are based on the conversion of these particles into photons in a magnetic field. An alternative scheme may involve the detection via a resonant atomic or molecular transition induced by resonant axion absorption. The signal obtained in this process is second order in the axion–electron interaction constant but may become first order if we allow interference between the axion-induced transition amplitude and the transition amplitude induced by the electromagnetic radiation that produces the axions.