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In the Fermionic Molecular Dynamics (FMD) approach [1] nuclei are described using Gaussian wave-packets as single-particle states. Many-body basis states are Slater determinants which are projected on parity, angular momentum and total linear momentum to restore the symmetries of the Hamiltonian. The FMD basis is very flexible and contains harmonic oscillator and Brink-type cluster configurations as special limiting cases. The widths of the wavepackets are variational parameters which together with the possibility to superimpose two wave-packets in a singleparticle states allows a successful description of extended halo states. An effective Hamiltonian derived from the realistice Argonne V18 interaction within the Unitary Correlation Operator Method (UCOM) is used for all nuclei. Recent measurements of the charge radii of the Neon isotopes 17−22 Ne by the COLLAPS group at ISOLDE triggered a study of the properties of these nuclei in the FMD approach and resulted in a joint publication [2]. Of particular interest here was the structure of 17 Ne. Whereas three-body cluster calculations found large s 2 components and therefore a halo-like structure, shell model calculations based on Coulomb displacement energies and magnetic moments predicted a small s 2 component. FMD configurations for the neon isotopes were obtained in a variation after parity projection procedure. For 17,18 Ne two minima were found which are essentially 15,16 O cores plus two protons in either s 2 or d 2 configurations. Because of the missing centrifugal barrier the s-orbits are much more extended. A large s 2 component in the ground state wave function is therefore related to a large charge radius. The calculated s 2 admixture is about 42 % for 17 Ne but only ρ (fm-3

Year: 2010

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