Probing Axion via M\"ossbauer Spectroscopy

TL;DR

This paper proposes using M"ossbauer spectroscopy of $^{109}$Ag to detect QCD axion dark matter by observing oscillations in nuclear energy levels, surpassing current laboratory bounds and exploring new axion mass ranges.

Contribution

It introduces a novel experimental approach using M"ossbauer spectroscopy to search for axion dark matter, extending sensitivity to higher masses beyond existing methods.

Findings

Derived constraints on axion parameters surpass other lab bounds.

Proposed experimental setup can detect time-varying signatures of axion fields.

Potential to explore a vast, previously inaccessible axion parameter space.

Abstract

We propose using the ultra-narrow 88 keV M\"ossbauer transition in $^{109}$Ag to search for QCD axion dark matter. The sub-eV axion field oscillates coherently, inducing a time-varying effective $\bar{\theta}_{\rm QCD}$ 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 M\"ossbauer 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.