Article révisé par les pairs
Résumé : Within a constrained Hartree-Fock calculation we investigate the effects of left-right asymmetric degrees of freedom associated with the channel 16O + 4He ↔ 20Ne. We find a large softness of 20Ne against octupole deformation. The optimal solution after restoration of the parity by means of a projection shows a pronounced 16O + 4He clustering. A generator coordinate calculation along the collective path confirms this conclusion. Once center-of-mass motion effects are taken into account a good agreement with experiment is found. © 1983.