A $\mathrm{^{136}Xe}$ nuclei capture electron neutrinos through charged-current (CC) interaction.
This lead to a excited state of $\mathrm{^{136}{Cs}: \nu_e + \mathrm{^{136}Xe} \rightarrow e^- +\mathrm{^{136}Cs} ~(1^+)}$.
This reaction can be used for low energy solar neutrino measurements and MeV scale mass fermionic dark matter searches.
The recent observation of low-lying isomeric states in $\mathrm{^{136}Cs~(1^+)}$ with lifetimes on the order of 100 ns implies that the CC interaction can be identified by a delayed-coincidence measurement in liquid scintillator detector.
This technique involves detecting a prompt signal consisting of the electron and most of the de-excitation $\gamma$-rays, followed by a delayed signal consisting of the remaining de-excitation $\gamma$-rays with energies below 140 keV.
KamLAND-Zen is an experiment designed to search for neutrinoless double-beta decay of $\mathrm{^{136}Xe}$.
KamLAND-Zen uses organic liquid scintillators dissolving 750 kg of xenon (91% enriched in $\mathrm{^{136}Xe}$) and has the world's largest exposure to the CC reaction.
We conducted a feasibility study of identifying the CC interaction in KamLAND-Zen.