This search identifies axionlike dark matter particles in a mass range using nuclear magnetic resonance in methanol, suggesting new detection methods.
We search for dark matter in the form of axionlike particles (ALPs) in the mass range 5.576741 \,neV/c² - 5.577733\,neV/c² by probing their possible coupling to fermion spins through the ALP field gradient. This is achieved by performing proton nuclear magnetic resonance spectroscopy on a sample of methanol as a technical demonstration of the Cosmic Axion Spin Precession Experiment Gradient (CASPEr-Gradient) Low-Field apparatus. Searching for spin-coupled ALP dark matter in this mass range with associated Compton frequencies in a 240 Hz window centered at 1.348570 MHz resulted in a sensitivity to the ALP-proton coupling constant of gₐₚ ≈ 3 × 10⁻²\,GeV⁻¹. This narrow-bandwidth search serves as a proof-of-principle and a commissioning measurement, validating our methodology and demonstrating the experiment's capabilities. CASPEr-Gradient Low-Field will probe the mass range from 4.1\,/c² to 17\,/c² with hyperpolarized samples to boost the sensitivity beyond the astronomical limits.
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Walter et al. (2025) studied this question.
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