Ground state properties and Coulomb dissociation of the deformed halo nucleus Ne31

The recently observed large cross sections for the Coulomb dissociation of Ne31 nucleus indicate that this nucleus takes a halo structure in the ground state. We analyze these experimental data using the particle-rotor model that takes into account the rotational excitation of the core nucleus Ne30. We show that the experimental data can be well reproduced when the quadrupole deformation parameter of Ne30 is around β₂=0.2∼0.3, at which the ground state takes the spin and parity of Iπ=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 β₂∼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 Ne31 in the Nilsson model analysis. We discuss briefly also a possibility of the Iπ=1/2⁺ configuration with β₂∼1 and β₂∼-0.4.