Observation of Low-Lying Isomeric States in Cs136 : A New Avenue for Dark Matter and Solar Neutrino Detection in Xenon Detectors

We report on new measurements establishing the existence of low-lying isomeric states in $^{136}\mathrm{Cs}$ using $\ensuremath{\gamma}$ rays produced in $^{136}\mathrm{Xe}(p,n)^{136}\mathrm{Cs}$ reactions. Two states with $\mathcal{O}(100)\text{ }\text{ }\mathrm{ns}$ lifetimes are placed in the decay sequence of the $^{136}\mathrm{Cs}$ levels that are populated in charged-current interactions of solar neutrinos and fermionic dark matter with $^{136}\mathrm{Xe}$. Xenon-based experiments can therefore exploit a delayed-coincidence tag of these interactions, greatly suppressing backgrounds to enable spectroscopic studies of solar neutrinos and dark matter.