Search for Solar Axions Produced by Primakoff Conversion Using Resonant Absorption by ¹⁶⁹Tm Nuclei

The search for resonant absorption of the Primakoff solar axions by $^{169}$Tm nuclei have been performed. Such an absorption should lead to the excitation of low-lying nuclear energy level: $A+^{169}$Tm $\to ^{169}$Tm$^*$ $\to ^{169}$Tm$ + \gamma$ (8.41 keV). The Si(Li) detector and $^{169}$Tm target placed inside the low-background setup were used for that purpose. As a result, a new restriction on the axion-photon coupling and axion mass was obtained: $g_{A\gamma}({GeV}^{-1})\cdot m_A(eV)\leq1.36\cdot10^{-5}$ (90% c.l.). In model of hadronic axion this restriction corresponds to the upper limit on axion mass - $m_A\leq$ 191 eV for 90% c.l.