Spectroscopic factors in the N=20 island of inversion: The Nilsson strong-coupling limit

Spectroscopic factors, extracted from one-neutron knockout and Coulomb dissociation reactions, for transitions from the ground state of Mg33 to the ground-state rotational band in Mg32, and from Mg32 to low-lying negative-parity states in Mg31, are interpreted within the rotational model. Associating the ground state of Mg33 and the negative-parity states in Mg31 with the 32[321] Nilsson level, the strong coupling limit gives simple expressions that relate the amplitudes (Cjℓ) of this wave function with the measured cross sections and derived spectroscopic factors (Sjℓ). To obtain a consistent agreement with the data within this framework, we find that one requires a modified 32[321] wave function with an increased contribution from the spherical 2p3/2 orbit as compared to a standard Nilsson calculation. This is consistent with the findings of large-scale shell model calculations and can be traced to weak binding effects that lower the energy of low-ℓ orbitals