Abstract
Intermediate energy single-neutron removal from 31Mg has been employed to investigate the transition into the N=20 island of inversion. Levels up to 5 MeV excitation energy in 30Mg were populated and spin-parity assignments were inferred from the corresponding longitudinal momentum distributions and γ-ray decay scheme. Comparison with eikonal-model calculations also permitted spectroscopic factors to be deduced. Surprisingly, the 02+ level in 30Mg 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 31Mg ground state. In addition, negative parity levels were identified for the first time in 30Mg, 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 30Mg. 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 30Mg.
Highlights
Intermediate energy single-neutron removal from 31Mg has been employed to investigate the transition into the N = 20 island of inversion
Levels up to 5 MeV excitation energy in 30Mg were populated and spin-parity assignments were inferred from the corresponding longitudinal momentum distributions and γ -ray decay scheme
Negative parity levels were identified for the first time in 30Mg, one of which is located at low excitation energy
Summary
Results for single-neutron removal from 31Mg. The observed levels (Ex), transition energies (Eγ ), intensities (Iγ ), direct fractional population (b) and corresponding cross sections (σ−1n ) are listed. High energy (and unobserved) γ -rays, would arise from any 1+ levels populated by 1s1/2 and/or 0d3/2 neutron removal; these are predicted to lie near 5 MeV (Fig. 5) and candidates are suggested in β-decay measurements [29].
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
