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 $\gamma$- 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 $|g_{Ae}(g^3_{AN}-g^0_{AN})|\leq 1.50\times 10^{-17}$ ($90\%$ C.L.) has been obtained for the axion–electron and axion–nucleon coupling constants, which corresponds to new constraints on the axion mass $m_A \leq 320$ eV and $m_A \leq 4.6$ eV in the KSVZ and DFSZ axion models, respectively.