Charge-exchange reactions on double-β decaying nuclei populating Jπ=2- states

The (He-3, t) charge-exchange reaction populating J(pi) = 2(-) states has been examined at 420 MeV incident energy for a series of double-beta decaying nuclei, i.e., Ge-76, Se-82, Zr-96, Mo-100, Te-128, Te-130, and Xe-136. The measurements were carried out at the Grand Raiden spectrometer of the Research Center for Nuclear Physics at the University Osaka with typical spectral resolution of 30-40 keV. It is found that the charge-exchange reaction leading to 2(-) spin-dipole states is selective to the sigma tau part of the interaction much similar to the observed selectivity to Gamow-Teller transitions. In the present case, the Delta L = 1 peak cross sections at finite momentum transfers are used to extract the spin-isospin part of the low-lying transition strength near the Fermi surface (i.e., E-x <= 5 MeV). Relative strength values are confronted with various model calculations, i.e., the interacting shell model, the quasiparticle random-phase approximation, and the Fermi surface quasiparticle model. The impact on the nuclear matrix elements for the neutrinoless double-beta decay is discussed.