Search for resonant absorption of solar axions by atomic nuclei

Search for resonant absorption of solar axions by 57Fe and 169Tm nuclei, leading to the excitation of the first nuclear level: 57Fe: A + 57Fe → 57Fe* → 57Fe + γ and A + 169Tm → 169Tm* → 169Tm + γ, has been performed. To this end, the energy spectra of the Si(Li) detector with 57Fe and 169Tm targets have been measured. The detector and targets were located in a low-background setup equipped with passive and active shields. A new upper limit on the axion mass: mA ≤ 330 eV (90% confidence level) has been established from the spectrum of 57Fe (30 days). Measurements with a 169Tm target during 8 days gave a new upper limit on the product of the axion-photon coupling constant and the axion mass: gAγ (GeV−1) × mA (eV) ≤ 2.9 × 10−4 (90% confidence level).