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

Hayakawa, Takehito; Mohr, P.*; Kajino, Toshitaka*; Chiba, Satoshi; Mathews, G. J.*

We analyze the production and freeze-out of the isomer Ta in the -process. We consider the influence of a possible low-lying intermediate ( = 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 ratio from the previous result. The isomer ratio changes from 0.39 to 0.38, whereas previously it was estimated that this transition could reduce the ratio to R = 0.18. This finding strengthens the evidence that La and Ta are coproduced by neutrino nucleosynthesis with an electron neutrino temperature of 4 MeV.