  Experimental studies for nuclear matrix elements (NMEs) for neutrinoless
double beta decays (DBDs) and astro-neutrino inverse beta decays (IBDs) are
crucial for neutrino studies beyond the standard model and the astro neutrino
reactions since theoretical model calculations for the NMEs are hard due to the
high sensitivities of the NMEs to the models. The NMEs associated with DBDs and
IBDs are found for the first time to be studied experimentally by measuring
electro-magnetic (gamma) transitions from isobalic analogue states (IASs) of
the DBD and IBD nuclei. They are used to help the theoretical model
calculations for them. The IAS gamma cross sections and the event rates are
estimated to show the feasibility of the experiments.
