Coulomb dissociation of the deformed halo nucleus 31Ne

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 ${\hat{I}}_2^2=0.2\sim 0.3$, at which the ground state takes the spin and parity of $I^{\ddot{I}}€$=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 ${\hat{I}}_2^2\sim 0.55$ 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 $I^{\ddot{I}}€$=1/2${}^{+}$ configuration with ${\hat{I}}_2^2\sim 1$ and ${\hat{I}}_2^2\sim -0.4$.

6 pages, 3 figures, 1 table