Search for solar axions using ${}^7\mathrm{Li}$

We describe a novel approach to the search for solar, near-monochromatic hadronic axions, the latter being suggested to be created in the solar core during $M1\mathrm{}$ transitions between the first excited level of ${}^7\mathrm{Li},$ at 478 keV, and the ground state. As a result of Doppler broadening, in principle these axions can be detected via resonant absorption by the same nuclide on the Earth. Excited nuclei of ${}^7\mathrm{Li}$ are produced in the solar interior by ${}^7\mathrm{Be}$ electron capture and thus the axions are accompanied by emission of ${}^7\mathrm{Be}$ solar neutrinos of energy 384 keV. An experiment was made which has yielded an upper limit on hadronic axion mass of 32 keV at the 95% confidence level.