Search for solar axions using 7 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 $M1$ 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.