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Excited states in 30 Mg have been populated to ∼6h and 5 MeV excitation energy with the 14 C( 18 O,2p) reaction. Firm spin assignments for states with J > 2h have been made in this nucleus. The level scheme is compared to shell-model calculations using the Universal sd effective interaction and the Monte Carlo shell model method. Calculations employing a full sd model space fail to reproduce the observed levels. The results indicate that excitations across the N = 20 gap are required at relatively low excitation energy to achieve a description of the data. The incorporation of the f 7/2 and p 3/2 orbitals into the model space gives improved results but indicate the need for further refinement of the models to reproduce the observed spectra.

There is sparse direct experimental evidence that atomic nuclei can exhibit stable 'pear' shapes arising from strong octupole correlations. In order to investigate the nature of octupole collectivity in radium isotopes, electric octupole (E3) matrix elements have been determined for transitions in 222,228 Ra nuclei using the method of sub-barrier, multi-step Coulomb excitation. Beams of the radioactive radium isotopes were provided by the HIE-ISOLDE facility at CERN. The observed pattern of E3 matrix elements for different nuclear transitions is explained by describing 222 Ra as pear-shaped with stable octupole deformation, while 228 Ra behaves like an octupole vibrator.

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