Re-examining the transition into the N=20 island of inversion: structure of ${}^{30}$Mg

Abstract

Intermediate energy single-neutron removal from ${}^{31}$Mg has been employed to investigate the transition into the N=20 island of inversion. Levels up to 5~MeV excitation energy in ${}^{30}$Mg were populated and spin-parity assignments were inferred from the corresponding longitudinal momentum distributions and $\gamma$-ray decay scheme. Comparison with eikonal-model calculations also permitted spectroscopic factors to be deduced. Surprisingly, the 0${}_2^{+}$ level in ${}^{30}$Mg was found to have a strength much weaker than expected in the conventional picture of a predominantly $2p-2h$ intruder configuration having a large overlap with the deformed ${}^{31}$Mg ground state. In addition, negative parity levels were identified for the first time in ${}^{30}$Mg, one of which is located at low excitation energy. The results are discussed in the light of shell-model calculations employing two newly developed approaches with markedly different descriptions of the structure of ${}^{30}$Mg. It is concluded that the cross-shell effects in the region of the island of inversion at Z=12 are considerably more complex than previously thought and that $np-nh$ configurations play a major role in the structure of ${}^{30}$Mg.

arXiv commentPhysics Letters B, Volume 779, 10 April 2018, Pages 124-129

References in corpus (12)

• Magic numbers in exotic nuclei and spin-isospin properties of {\it NN} interaction
• A new effective interaction for $0\hslash \omega$ shell model calculations in the sdpf valence space
• The merging of the islands of inversion at N=20 and N=28
• Systematics of intermediate-energy single-nucleon removal cross sections
• One-neutron removal reactions on light neutron-rich nuclei
• Exotic neutron-rich medium-mass nuclei with realistic nuclear forces
• Shape coexistence near the neutron number N=20: First identification of the E0 decay from the deformed 0^+_2 state in 30Mg
• Initial State Dependence of the Breakup of Weakly Bound Carbon Isotopes
• Core Transitions in the Breakup of Exotic Nuclei
• Structure of 23Al from one-proton breakup reaction and astrophysical implications
• Extended sudden approximation model for high-energy nucleon removal reactions
• Particle removal reactions with deformed projectiles

Cited by in corpus (5)

• A two-neutron halo is unveiled in ${}^{29}$F
• Shell evolution approaching the N=20 island of inversion: Structure of 29Mg
• Intruder configurations in ${}^{29}$Ne at the transition into the island of inversion: Detailed structure study of ${}^{28}$Ne
• Structure of ${}^{30}$Mg explored via in-beam $\gamma$-ray spectroscopy
• Coexisting normal and intruder configurations in ${}^{32}$Mg