Atomic spectroscopy can aid the search for ultralight dark matter.
Ken Van Tilburg at Stanford University, California, and his team measured the energy emitted as atoms of the rare-earth element dysprosium transitioned between two electronic states of very similar energy over a two-year period.
They looked for fluctuations in this energy over time, which would reveal short-term, local changes in the strength of the electromagnetic force. These could be caused by interactions with certain ultralight dark-matter particles.
No fluctuations were observed, meaning that any such dark-matter particles interacting would have to be heavier than 3 × 10−18 electronvolts or would have to interact very weakly. The results improve on previous bounds for the strength of such interactions by four orders of magnitude. If similar measurements were performed with atomic clocks, the limits might be improved by another order of magnitude.
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Tighter limits on dark matter. Nature 523, 130 (2015). https://doi.org/10.1038/523130c
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DOI: https://doi.org/10.1038/523130c
