Eur. Phys. J. A 15, 157-160 (2002)
DOI: 10.1140/epja/i2001-10245-5

Shape coexistence and the shell closure far from stability by inelastic scattering

W. Mittig¹, H. Savajols¹, D. Baiborodin^{1, 2}, J.M. Casandjian¹, C.E. Demonchy¹, P. Roussel-Chomaz¹, F. Sarazin¹, Z. Dlouhý², J. Mrazek², A.V. Belozyorov³, S.M. Lukyanov³, Y.E. Penionzhkevich³, N. Alamanos⁴, A. Drouart⁴, A. Gillibert⁴, C. Jouanne⁴, V. Lapoux⁴, E. Pollacco⁴, A. Korichi⁵ and J.A. Scarpaci<sup>6

1</sup>  GANIL (DSM/CEA, IN2P3/CNRS), BP 5027, 14076 Caen Cedex 5, France
²  Nuclear Physics Institute, ASCR, 25068 Rez, Czech Republic
³  FLNR, JINR, Dubna, P.O. Box 79, 101 000 Moscow, Russia
⁴  CEA/DSM/DAPNIA/SPhN, Saclay, 91191 Gif-sur-Yvette Cedex, France
⁵  CSNSM, F-91405 Campus Orsay, France
⁶  IPN, F-91406 Orsay Cedex, France

mittig@ganil.fr

(Received: 21 March 2002 / Published online: 31 October 2002)

Abstract
Following mass measurements in the region N=20 and N=28, we have studied inelastic nuclear scattering for the nuclei ³⁴Si, ³³Al and ³²Mg. No evidence for a low-lying shape isomeric 0 ⁺ state was found in ³⁴Si, and an upper limit for the population cross-section could be established, rendering its existence very unlikely. A new transition was found in ³³Al, that is a good candidate for a 2p-2h state and therefore a determination of the 2p-2h gap at N=20. Inelastic nuclear scattering strongly excites 3 ^- states, as seen in ³⁴Si. A strong transition was found in ³²Mg that should correspond to the first 3 ^- in this nucleus, lying very low as compared to theory and systematics in this region.

PACS
21.10.Re - Collective levels.
25.60.-t - Reactions induced by unstable nuclei.

© Società Italiana di Fisica, Springer-Verlag 2002