First trap-assisted decay spectroscopy of the $^{81}$Ge ground state
Résumé
The $\beta $-delayed $\gamma $ spectroscopy of $^{81}$As has been performed using a purified beam of $^{81}$Ge $(9/2^+)$ ground state at the Ion Guide Isotope Separator On-Line facility (IGISOL). The $^{81}$Ge$^+$ ions were produced using proton-induced fission of $^{232}$Th and selected with the double Penning trap JYFLTRAP for the post-trap decay spectroscopy measurements. The low-spin $(1/2^+)$ isomeric-state ions $^{81m}\hbox {Ge}^+$ were not observed in the fission products. The intrinsic half-life of the $^{81}$Ge ground state has been determined as $T_{1/2}=6.4(2)~\hbox {s}$, which is significantly shorter than the literature value. A new level scheme of $^{81}$As has been built and is compared to shell-model calculations.
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