Observation of low-lying isomeric states in 136Cs with implications for solar neutrino detection

We report new measurements establishing the existence of low-lying isomeric states in 136Cs. These measurements are carried out at the TUNL Tandem Laboratory using γ rays produced in 136Xe(p,n)136Cs reactions. Two states with O(100) ns lifetimes are placed in the decay sequence of the 136Cs levels that are populated in charged-current interactions of solar neutrinos and fermionic dark matter with 136Xe. 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. We compare our results with shell model calculations and recent experimental results from 138Ba(d,alpha)136Cs reactions.