Unveiling the Intruder Deformed02+State inSi34

Abstract

The 0 þ 2 state in 34 Si has been populated at the GANIL-LISE3 facility through the decay of a newly discovered 1 þ isomer in 34 Al of 26(1) ms half-life. The simultaneous detection of e þ e À pairs allowed the determination of the excitation energy Eð0 þ 2 Þ ¼ 2719ð3Þ keV and the half-life T 1=2 ¼ 19:4ð7Þ ns, from which an electric monopole strength of 2 ðE0Þ ¼ 13:0ð0:9Þ Â 10 À3 was deduced. The 2 þ 1 state is observed to decay both to the 0 þ 1 ground state and to the newly observed 0 þ 2 state [via a 607(2) keV transition] with a ratio Rð2Gathering all information, a weak mixing with the 0 þ 1 and a large deformation parameter of ¼ 0:29ð4Þ are found for the 0 þ 2 state, in good agreement with shell model calculations using a new SDPF-U-MIX interaction allowing np-nh excitations across the N ¼ 20 shell gap.

Ground-state configuration of neutron-rich Al35 via Coulomb breakup

“…After constraining a maximum limit of the spectroscopic factor of the d orbital to 1.0, the spectroscopic factors for the p and f orbitals, obtained from fitting of the data, are 0.48(0.08) and 0.24 +0. 42 −0.24 , respectively. In conclusion, the enhanced Coulomb dissociation cross section of 35 Al clearly suggests that the neutron may occupy orbitals which are a combination of sd and pf orbitals.…”

“…In 34 Al, an isomeric state [T 1/2 = 26(1) ms] at 0.46 MeV (1 + ) has been reported [42]. Hence, it is necessary to consider the core as a system with an admixture of a 4 − [T 1/2 = 54.5(1) ms] [43] ground state with the 1 + isomeric state [42]. The allowed spin and parity corresponding to the former and latter configurations are (7/2; 9/2) − and (1/2; 3/2) + , respectively.…”

“…The convoluted curve has been fitted with the experimental data using a chi-square minimization procedure. In 34 Al, an isomeric state [T 1/2 = 26(1) ms] at 0.46 MeV (1 + ) has been reported [42]. Hence, it is necessary to consider the core as a system with an admixture of a 4 − [T 1/2 = 54.5(1) ms] [43] ground state with the 1 + isomeric state [42].…”

High-precision quadrupole moment reveals significant intruder component inAl201333ground state

“…33 13 Al 20 is thought to be a key isotope as the transition into the island is particularly rapid in the N = 20 isotones. In 34 14 Si 20 a 2p-2h intruder state was recently found at 2719 keV [12], which comes down almost 4 MeV in 32 12 Mg 20 , where it becomes the ground state, lying 1058 keV below the normal configuration [13]. 33 Al is therefore expected to have a transitional nature, with potentially a significant amount of intruder admixtures in its ground state.…”

“…Warburton et al [4] originally predicted that the island of inversion around N = 20 contains the 10 Ne, 11 Na, and 12 Mg isotopes with 20 N 22. Since then, an extensive research program has focused on the characterization of the low-energy properties of these isotopes and their neighbors, in * gerda.neyens@kuleuven.be † Present address: Department of Physics, Tokyo Institute of Technology, 2-12-1 Oh-okayama, Meguro-ku, Tokyo 152-8551, Japan.…”