Intruder configurations in the ground state of 30Ne

Hongna Liu ,E Ideguchi,T Motobayashi,P Doornenbal,M Matsushita,N Kobayashi,Y Kondo,D Steppenbeck,Y Togano,H Scheit,S Michimasa,M Takechi,N Aoi,A Poves,H Baba,Satoshi Takeuchi ,G Lee ,Handing Wang ,Ka Li ,J Lee ,J A Tostevin ,H Sakuraï ,Yutaka Utsuno

doi:10.1016/j.physletb.2017.01.052

Abstract

We report on the first detailed study of intruder configurations in the ground state of 30Ne by means of the 12C(30Ne,29Ne+γ)X one-neutron knockout reaction at 228 MeV/nucleon. Using a combined analysis of individual parallel momentum distributions and partial cross sections we find: (a) comparable p- and d-wave removal strength to 29Ne final states with excitation energies below 200 keV, and (b) significant p-wave removal strength to the 620 keV state of 29Ne, and (c) no evidence for f-wave intruder strength leading to bound 29Ne final states. The SDPF-U-MIX shell model calculation in the sd-pf model space provides a better overall agreement with the measured energy levels of 29Ne and the fp-intruder amplitudes in 30Ne than the SDPF-M prediction, suggesting that the refinement of the sd-pf cross shell interaction and extension of the model space to include the 2p1/2 and 1f5/2 levels are important for understanding the island of inversion.

Highlights

[7] and shell-model [8,9,10,11,12] approaches
We find almost equal amounts of 29Ne with l = 1 and l = 2 in the extracted momentum distribution for bound final states with excitation energies below 200 keV, suggesting that 29Ne has a ground state of 3/2− or 3/2+
Taken together with the measured enhanced interaction cross section of 29Ne with respect to 28Ne, which indicated low-l valence neutron configurations [33], the 3/2− assignment was adopted for the ground state of 29Ne in the current analysis

Summary

Introduction

[7] and shell-model [8,9,10,11,12] approaches. It has been discussed that in neutron-rich nuclei the reduced T = 0 tensor forces suppress the separation between the 1d3/2 and 1 f7/2 orbitals, leading to the intruder dominance by particle–hole excitations across the N = 20 shell gap [10]. We report on the 1n knockout measurement from 30Ne. The combined analysis of the momentum distributions and partial cross sections for individual bound 29Ne final states allows the spin-parity assignment for the low-lying states of 29Ne as well as a quantitative study of the respective f p-shell intruder amplitudes in the ground state of 30Ne. This new experimental information can provide a stringent test of theory and shed new light on the understanding of the island of inversion.

Results

Conclusion