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$$alpha$$-$$gamma$$核分光による超重核の核構造研究

$$alpha$$-$$gamma$$ spectroscopy of superheavy nuclei

浅井 雅人

Asai, Masato

原子力機構タンデム加速器を用いて超重核の$$alpha$$-$$gamma$$核分光実験を行った。$$^{248}$$Cm標的を用いた熱い融合反応により$$^{255}$$No, $$^{257}$$No, $$^{259}$$No, $$^{261}$$Rfを合成し、ガスジェット搬送した後、それらの$$alpha$$崩壊に伴う$$gamma$$線を回転円盤型測定装置を用いて観測した。その結果、陽子数101,中性子数153を超える領域に位置する超重核の基底状態及び励起準位のエネルギー,スピン・パリティ,中性子軌道配位を初めて実験的に同定することに成功した。中性子数152から162の領域で中性子の一粒子軌道のエネルギー順序が逆転していることを明らかにし、理論計算との比較からその原因について考察した。

$$alpha$$-$$gamma$$ spectroscopy of superheavy nuclei have been performed at JAEA tandem accelerator. The nuclei $$^{255}$$No, $$^{257}$$No, $$^{259}$$No, and $$^{261}$$Rf were produced by the cold-fusion reactions with a $$^{248}$$Cm target, and were transported with a gas-jet transport technique to a rotating wheel $$alpha$$-$$gamma$$ detection system, where $$gamma$$ rays associated with the $$alpha$$ decays of these nuclei were observed. Energies, spin-parities, and neutron configurations of the ground- as well as excited states in these nuclei have been successfully identified. These results suggest that the order of neutron orbitals should be inverted between the neutron number 152 and 162. The cause of this inversion is discussed through the comparison with theoretical calculations.

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