Reanalysis of the (J=5) state at 592 keV in Ta180 and its role in the ν-process nucleosynthesis of Ta180 in supernovae

We analyze the production and freeze-out of the isomer Ta180m in the ν-process. We consider the influence of a possible low-lying intermediate (J=5) state at 592 keV using a transition width estimated from the measured half-life. This more realistic width is much smaller than the previous estimate. We find that the 592-keV state leads only to a small reduction of the residual isomer population ratio from the previous result; that is, considering this better estimate for the transition width, the isomer population ratio changes from R=0.39 to R=0.38, whereas previously it was estimated that this transition could reduce the ratio to R=0.18. This finding strengthens the evidence that La138 and Ta180 are coproduced by neutrino nucleosynthesis with an electron neutrino temperature of kT≈4 MeV.