Coulomb dissociation of the deformed halo nucleus 31Ne

TL;DR

This paper analyzes Coulomb dissociation data of the deformed halo nucleus 31Ne using a particle-rotor model, showing the importance of core deformation and rotational excitation in understanding its structure.

Contribution

It introduces a detailed particle-rotor model analysis that accounts for core deformation and rotational excitation, providing new insights into the ground state configuration of 31Ne.

Findings

Experimental data are well reproduced with core deformation parameter β2≈0.2–0.3.

The ground state likely has spin-parity 3/2−, corresponding to Nilsson level [330 1/2].

Configurations with higher deformation (β2≈0.55) are excluded when finite core excitation energy is considered.

Abstract

The recently observed large cross sections for the Coulomb dissociation of $^{31}$Ne nucleus indicate that this nucleus takes a halo structure in the ground state. We analyse these experimental data using the particle-rotor model, that takes into account the rotational excitation of the core nucleus $^{30}$Ne. We show that the experimental data can be well reproduced when the quadrupole deformation parameter of $^{30}$Ne is around $\beta_2=0.2\sim0.3$, at which the ground state takes the spin and parity of $I^\pi$=3/2$^-$. This state corresponds to the Nilsson level [330 1/2] in the adiabatic limit of the particle-rotor model. On the other hand, the state corresponding to the Nilsson level [321 3/2] with $\beta_2\sim 0.55$ can be excluded when the finite excitation energy of the core is taken into account, even though this configuration is a candidate for the ground state of $^{31}$Ne in the Nilsson model analysis. We discuss briefly also a possibility of the $I^\pi$=1/2$^+$ configuration with $\beta_2\sim 1$ and $\beta_2\sim -0.4$.