Probing Axion via Mössbauer Spectroscopy

Abstract

We propose using the ultra-narrow 88 keV Mössbauer transition in $^{109}$Ag to search for QCD axion dark matter. The sub-eV axion field oscillates coherently, inducing a time-varying effective $\barθ_{\rm QCD}$ angle. This, in turn, modulates the nuclear binding energy. From existing linewidth measurements, we derive constraints on the $f_a^{-1}$-$m_a$ plane that already surpass other laboratory bounds. We further detail an experimental setup to directly probe this time-dependent signature via precision Mössbauer spectroscopy in the gravitational potential. This Letter demonstrates that this approach can significantly extend search capability and probe a vast, unexplored region of axion parameter space. Particularly, this setup can probe axion masses beyond the reach of existing experiments, such as atomic-clock measurements, offering a powerful new way for exploring higher-mass axion dark matter. The sensitivity has the potential to be further improved with advancing experimental capabilities.

Figures (2)

• Figure 1: The illustrative experimental setup.
• Figure 2: Here we show the sensitivity projection using $^{109}$Ag Mössbauer spectroscopy. The curve labeled "Ag 109" is derived by reinterpreting existing measurements Bayukov2009. It is obtained by requiring that the axion-induced peak shift be smaller than the experimental linewidth precision of $7.0 \Gamma_0$, for a source-absorber separation of $d= 0.24$m. The two dashed lines represent the projected sensitivities in the benchmark Scenario A and B. Other experimental sensitivities on the $f_a^{-1}-m_a$ plane are overlaid.