Gamow-Teller strength in the exotic odd-odd nuclei 138La and 180Ta and its relevance for neutrino nucleosynthesis

The Gamow-Teller strength distributions below the particle threshold in La-138 and Ta-180, deduced from high-resolution measurements of the (He-3,t) reaction at 0 degrees, allow us to evaluate the role of charged-current reactions for the production of these extremely rare nuclides in neutrino-nucleosynthesis models. The analysis suggests that essentially all La-138 in the Universe can be made that way. Neutrino nucleosynthesis also contributes significantly to the abundance of Ta-180 but the magnitude depends on the unknown branching ratio for population of the long-lived isomer.