New nuclide $^{139}$Tb and (EC+ $\beta ^{+}$) decay of $^{138,139}$Gd

Xie Yuanxiang; Xu Shuwei; Li Zhankui; Yu Yong; Pan Qiangyan; Wang Chunfang; Zhang Tianmei

EPJ

New nuclide ¹³⁹Tb and (EC+ $\beta ^{+}$ ) decay of ^138,139Gd

Xie Yuanxiang - Xu Shuwei - Li Zhankui - Yu Yong - Pan Qiangyan - Wang Chunfang - Zhang Tianmei

Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000, P.R. China

Received: 2 June 1999 / Revised version: 4 August 1999 Communicated by D. Schwalm

Abstract
The unknown isotope ¹³⁹Tb and the known isotopes ^138,139Gd were produced in the ³⁶Ar+¹⁰⁶Cd reaction and studied by using a He-jet tape transport system in combination with X- $% \gamma$ and $\gamma$ - $\gamma$ coincidence measurements. The half-lives of ¹³⁹Tb, ^139gGd, ^139mGd and ¹³⁸Gd were determined to be 1.6(2), 5.8(9), 4.8(9) and 4.7(9) s, respectively. Partial (EC+ $\beta ^{+}$ ) decay schemes of ^139gGd, ^139mGd and ¹³⁸Gd were proposed for the first time.