# Metastable Nuclear Isomers as Dark Matter Accelerators

## TL;DR

This paper proposes a novel method to detect inelastic and strongly interacting dark matter by observing the collisional de-excitation of metastable nuclear isomers, which could reveal interactions otherwise hard to detect.

## Contribution

It introduces the idea of using metastable nuclear isomers to probe dark matter interactions that are weakly constrained by existing experiments.

## Key findings

- Metastable nuclear isomers can be de-excited by heavy dark matter particles.
- Existing nuclear waste sources can be used as isomer sources for dark matter detection.
- The proposed method can complement current dark matter search techniques.

## Abstract

Inelastic dark matter and strongly interacting dark matter are poorly constrained by direct detection experiments since they both require the scattering event to deliver energy from the nucleus into the dark matter in order to have observable effects. We propose to test these scenarios by searching for the collisional de-excitation of meta-stable nuclear isomers by the dark matter particles. The longevity of these isomers is related to a strong suppression of $\gamma$- and $\beta$-transitions, typically inhibited by a large difference in the angular momentum for the nuclear transition. The collisional de-excitation by dark matter is possible since heavy dark matter particles can have a momentum exchange with the nucleus comparable to the inverse nuclear size, hence lifting tremendous angular momentum suppression of the nuclear transition. This de-excitation can be observed either by searching for the direct effects of the decaying isomer, or through the re-scattering or decay of excited dark matter states in a nearby conventional dark matter detector setup. Existing nuclear isomer sources such as naturally occurring $^{180m}$Ta, $^{137m}$Ba produced in decaying Cesium in nuclear waste, $^{177m}$Lu from medical waste, and $^{178m}$Hf from the Department of Energy storage can be combined with current dark matter detector technology to search for this class of dark matter.