从微观结构到反应可观测量描述单中子晕核新进展

With the development of radioactive ion beam physics, the exotic phenomena appear in exotic nuclei and arouse great interest, such as the inversion of islands on shell evolution, halo nuclei, cluster effect, etc. In this paper, we review the progress on 1n halo nuclei from both experimental and theoretical aspects. Taking the heavier and heaviest 1n p-wave halo nuclei ³¹Ne and ³⁷Mg as examples, we study the effects from deformation, resonant states and pairing correlations in the formation of a halo nucleus via our newly developed approach. Firstly, we utilized the analytical continuation of the coupling constant (ACCC) method, based on a relativistic mean field (RMF) structure theory with the Bardeen-Cooper-Schrieffer (BCS) approximation—the RAB model, which includes the contributions from the single-particle resonant states around Fermi surface and the pairing correlations with the coupling of the bound states and resonant states. We modify the Glauber reaction model so that the densities from the microscopic theory can be directly used for the calculations and the results are improved by ~50 mb compared with those with multi-set of the Gaussian-fitted densities. In this way, we achieved a unified description from the microscopic structure to reaction observables for the case of neutron-rich isotopes on a carbon target and succeeded in the identification of 1n p-wave halo nucleus ³¹Ne for the first time. Furthermore, we adopted the deformed relativistic Hartree-Bogoliubov theory in continuum (DRHBc) incorporated with the Glauber model to study the effects from the deformation, discretized continuum and pairing correlations on the reaction observables. We found that the previous overestimated results are largely modified by 30% for the reaction cross sections, 1n removal cross sections and momentum distributions for halo nucleus ³¹Ne on a carbon target and agree with the experimental data.In this scheme, we computed the reaction cross sections of ³⁷Mg bombarding a carbon target at 240 MeV/nucleon and found that most of the results agree well with the experimental data within the uncertainty of 1σ. Our predicted increase of the cross section from ³⁶Mg to ³⁷Mg is twice than that from ³⁴Mg to ³⁵Mg, consistent with a halo structure in ³⁷Mg. Additionally, our calculated narrow longitudinal momentum distribution of ³⁶Mg residues from ³⁷Mg+¹²C breakup reaction agree well with the data and imply a nuclear size much larger than ³⁵Mg. Moreover, our study shows a dominant p-wave contribution to the longitudinal momentum distribution, supporting the conclusion that ³⁷Mg is a p-wave halo nucleus.In total, the spherical structure combined with the spherical reaction model (i.e., RAB+Glauber model) can comprehensively describe 1n halo nucleus ³¹Ne, but overestimate the observables by 30%. The deformation effect is crucial for the improvement of the predictions. The DRHBc+Glauber model has turned out to be an efficient tool to unified describe the halo characteristics in ³¹Ne and ³⁷Mg from nuclear structures to reaction dynamics, which casts a light on new 1n p-wave halo candidates in the near future.