Speaker
Description
The neutron-rich, lighter actinoid isotopes are important for revealing the origin of the heavy r-process elements beyond Pb, such as uranium. In the recent observations, the r-process element was identified in the kilonova AT2017fgo associated with the neutron-star merger. Moreover, the theoretical study has shown that the radioactive isotopes produced by the r-process play an important role as a heating source for the kilonova’s ejecta. Theoretical investigations indicate that energy release via the spontaneous fission of 254Cf is dominant among them.
The abundance of 254Cf produced in the r-process nucleosynthesis strongly depends on the nuclear masses of the neutron-rich isotopes along the predicted r-process path. However, the location of the predicted r-process path is far from the β-stable line, and the variance of theoretically predicted masses becomes larger toward the neutron-rich region, where experimental information is lacking. In particular, the difference in the nuclear mass model significantly changes the predicted kilonova light curve. Therefore, comprehensive mass measurements of the neutron-rich trans-Pb isotopes are required. However, the neutron-rich actinoid region had long been unexplored territory due to the difficulties with production methods.
Multinucleon transfer (MNT) reactions have recently been discussed as a new method to access the unreached neutron-rich region. In this presentation, we report mass measurements of new neutron-rich americium isotopes produced via the MNT reaction with 248Cm, as the first step toward exploring the Terra Incognita of the nuclear chart.
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