-decay half-lives of new neutron-rich rare-earth isotopes Pm, Sm, and Gd

中性子過剰新希土類核種、Pm, Sm, Gdの半減期

市川 進一; 浅井 雅人  ; 塚田 和明  ; 羽場 宏光*; 永目 諭一郎 ; 柴田 理尋*; 阪間 稔*; 小島 康明*

Ichikawa, Shinichi; Asai, Masato; Tsukada, Kazuaki; Haba, Hiromitsu*; Nagame, Yuichiro; Shibata, Michihiro*; Sakama, Minoru*; Kojima, Yasuaki*

ガスジェット搬送装置と結合したオンライン同位体分離器を用い、ウランの陽子誘起核分裂で生成する中性子過剰未知希土類核、Pm, Sm, Gdを発見し、それぞれの半減期を1.50.2s, 2.40.5s, 4.81.0sと決定した。また、Gdについては部分崩壊図式を構築した。さらに、以前に見いだしたTbの半減期を精度よく再測定し25.62.2sと決定した。本研究で見いだした新核種の半減期は、大局的理論で予測された半減期と良い一致を見た。

The new neutron-rich raer-earth isotopes Pm, Sm, and Gd produced in the proton-induced fission of 238U were identified using the JAERI on-line isotope separator (JAERI-ISOL) coupled to a gas-jet transport sysetm. The half-lives of Pm, Sm, and Gd were determined to be 1.50.2s, 2.40.5s, and 4.81.0s, respectively. The partial decay scheme of Gd wes constructed for - coincidence data. The improved half-life values of 25.62.2s wes obtained for the previously identified isotope Tb. The half-lives measured in the present study are in good agreement with the theoretical predictions calculated by the second generation of the gross theory with the atomic masses evaluated by the Audei and Wapstra.