New Constraints on the Axion–Electron Coupling Constant for Solar Axions

The resonant excitation of the 83 Kr first excited nuclear level ( E = 9.4 keV) by solar axions whose fluxes depend on the axion–electron coupling constant g Ae is sought. The γ- and X-ray photons and the conversion and Auger electrons from the excited-level relaxation are detected with a gas proportional counter of a low-background detector in the underground Baksan Neutrino Observatory (Institute for Nuclear Research, Russian Academy of Sciences). As a result, a new constraint $${\text{|}}{{g}_{{Ae}}}(g_{{AN}}^{3} - g_{{AN}}^{0}){\text{|}}$$ ≤ 1.50 × 10 –17 (90% C.L.) has been obtained for the axion–electron and axion–nucleon coupling constants, which corresponds to new constraints on the axion mass m A ≤ 320 eV and m A ≤ 4.6 eV in the KSVZ and DFSZ axion models, respectively.