Mass andβDecay of the New IsotopeMg29: Systematics of Masses ofTz=52Nuclides in the2s−1dShell

Abstract

Measurements of the mass, half-life, and $\ensuremath{\beta}$ decay of the new isotope $^{29}\mathrm{Mg}$ are reported. Produced by the $^{18}\mathrm{O}(^{13}\mathrm{C},2p)^{29}\mathrm{Mg}$ reaction, this activity was periodically transferred to remotely located Ge(Li) and NE 102 detectors. $\ensuremath{\gamma}$-ray energies (in keV) and relative intensities for the $^{29}\mathrm{Al}$ daughter transitions are 960.3 \ifmmode\pm\else\textpm\fi{} 0.4 (52 \ifmmode\pm\else\textpm\fi{} 18), 1397.7 \ifmmode\pm\else\textpm\fi{} 0.4 (${64}_{\ensuremath{-}20}^{+30}$), 1430 \ifmmode\pm\else\textpm\fi{} 1.5 (34 \ifmmode\pm\else\textpm\fi{} 17), 1753.8 \ifmmode\pm\else\textpm\fi{} 0.4 (22 \ifmmode\pm\else\textpm\fi{} 5), and 2223.7 \ifmmode\pm\else\textpm\fi{} 0.4 (100 \ifmmode\pm\else\textpm\fi{} 6). The $^{29}\mathrm{Al}$ excitation energies (in keV) and relative $\ensuremath{\beta}$ branching intensities are 1397.7 \ifmmode\pm\else\textpm\fi{} 0.4 (${64}_{\ensuremath{-}28}^{+35}$), 1753.8 \ifmmode\pm\else\textpm\fi{} 0.4 (10), 2223.8 \ifmmode\pm\else\textpm\fi{} 0.4 (55 \ifmmode\pm\else\textpm\fi{} 22), and 3184.0 \ifmmode\pm\else\textpm\fi{} 0.6 (100 \ifmmode\pm\else\textpm\fi{} 35). Upper limits on other possible transitions are given. $^{29}\mathrm{Mg}$ decays with a half-life of 1.20 \ifmmode\pm\else\textpm\fi{} 0.13 sec, measured by the decay of the prominent 2224-keV $\ensuremath{\gamma}$ ray. The decay of $^{29}\mathrm{Mg}$ is discussed in terms of the Nilsson model. By measuring the spectrum of pulses in the NE 102 detector coincident with 2224-keV $\ensuremath{\gamma}$ rays, the mass excess for $^{29}\mathrm{Mg}$ has been determined to be -10 590 \ifmmode\pm\else\textpm\fi{} 400 keV, disagreeing by 1.7 \ifmmode\pm\else\textpm\fi{} 0.5 MeV from a previous report. The present mass for $^{29}\mathrm{Mg}$ is combined with all other information concerning masses of ${T}_{z}=\frac{5}{2}$ nuclides in the $2s\ensuremath{-}1d$ shell, and the results are compared with predictions based upon measured masses closer to stability using the transverse relationship of Garvey. When the differences between the measured and predicted values are plotted against atomic weight, systematic effects are evident.