Coherent axion-photon transformations in the forward scattering on atoms

Abstract

In certain laboratory experiments the production and/or detection of axions is due to the photon-axion transformations in a strong magnetic field. This process is coherent, and the rate of the transformation is proportional to the length $l$ and magnitude $B$ of the magnetic field squared, $\sim l^2B^2$. In the present paper, we consider coherent production of axions due to the forward scattering of photons on atoms or molecules. This process may be represented as being due to an effective electromagnetic field which converts photons to axions. We present analytical expressions for such effective magnetic and electric fields induced by resonant atomic M0 and M1 transitions, as well as give some numerical estimates for these fields. The corresponding experiments would allow one to measure the electron-axion coupling constant $g_{ae}$ in the same way as the photon-axion coupling $g_{a\gamma}$ is studied.