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In-Beam γ -Ray Spectroscopy of Mg 34 , 36 , 38 : Merging the N = 20 and N = 28 Shell Quenching

Year: 2013

Type: article

Abstract: Neutron-rich $N=22$, 24, 26 magnesium isotopes were studied via in-beam $\ensuremath{\gamma}$-ray spectroscopy at the RIKEN Radioactive Isotope Beam Factory following secondary fragmentation reactions on a carbon target at $\ensuremath{\approx}200\text{ }\text{ }\mathrm{MeV}/\mathrm{\text{nucleon}}$. In the one- and two-proton removal channels from $^{39}\mathrm{Al}$ and $^{40}\mathrm{Si}$ beams, two distinct $\ensuremath{\gamma}$-ray transitions were observed in $^{38}\mathrm{Mg}$, while in the one-proton removal reaction from $^{37}\mathrm{Al}$ a new transition was observed in addition to the known ${2}_{1}^{+}\ensuremath{\rightarrow}{0}_{\mathrm{g}.\mathrm{s}.}^{+}$ decay. From the experimental systematics and comparison to theoretical predictions it is concluded that the transitions belong to the ${2}_{1}^{+}\ensuremath{\rightarrow}{0}_{\mathrm{g}.\mathrm{s}.}^{+}$ and ${4}_{1}^{+}\ensuremath{\rightarrow}{2}_{1}^{+}$ decays in $^{36}\mathrm{Mg}$ and $^{38}\mathrm{Mg}$, respectively. For $^{34}\mathrm{Mg}$, previously reported ${2}_{1}^{+}$ and ${4}_{1}^{+}$ level energies were remeasured. The deduced $E({4}_{1}^{+})/E({2}_{1}^{+})$ ratios for $^{34,36,38}\mathrm{Mg}$ of 3.14(5), 3.07(5), and 3.07(5) are almost identical and suggest the emergence of a large area of deformation extending from the $N=20$ to the $N=28$ shell quenching.

Source: Physical Review Letters

DOI: 10.1103/physrevlett.111.212502