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HK: Hadronen und Kerne

HK 13: Kernspektroskopie, leichte Kerne I

HK 13.5: Vortrag

Montag, 24. März 1997, 18:15–18:30, HS E

New region of deformation: the neutron-rich sulfur isotopes — •M. Hellström¹, H. Scheit², T. Glasmacher², B. A. Brown², J. A. Brown², P. D. Cottle³, P. G. Hansen², R. Harkewicz², R. W. Ibbotson², J. K. Jewell³, K. Kemper³, D. J. Morrissey², M. Steiner², P. Thirolf², and M. Thoennessen² — ¹Gesellschaft für Schwerionenforschung, Darmstadt, Germany — ²National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, Michigan, USA — ³Florida State University, Tallahassee, Florida, USA

The energies, lifetimes and B(E2;0_g.s.⁺→ 2₁⁺) values of the 2₁⁺ states of ^38,40,42S and ^44,46Ar have been measured at the National Superconducting Cyclotron Laboratory at Michigan State University using intermediate-energy (35-40 A MeV) Coulomb excitation. The nuclei were produced via fragmentation of up to 80 A MeV ⁴⁸Ca and ⁴⁰Ar beams from the K1200 cyclotron and isotopically separated using the A1200 projectile fragment separator before interacting with a Au target. Gamma-rays following the excitation of the secondary beams were detected in an array of position-sensitive NaI detectors surrounding the Au target, allowing Doppler-shift correction of the transition energies. The results show that ^40,42S have |β₂| values around 0.3, indicating the presence of a new region of deformed nuclei near N=28. The data on the 2₁⁺ state in ⁴⁶Ar demonstrate that the N=28 major shell gap persists at Z=18. Both mean field calculations and shell model calculations using empirical interactions can approximately reproduce the behavior of the 2₁⁺ states of ^40,42S.