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Conference on Nuclei at the Limits, Argonne, Illinois : États-Unis (2004)
Shape coexistence in light krypton isotopes
E. Clément1, A. Görgen1, E. Bouchez1, A. Chatillon1, W. Korten1, Y. Le Coz1, C. Theisen1, C. Andreoiu, F. Becker, B. Blank2, C. Borcea, A. Buta, P. Butler, J.M. Casandjian3, W.N. Catford, T. Czosnyka, A. Emsallem4, G. De France3, J. Genevey5, J. Gerl, F. Hannachi2, K. Hauschild6, R.-D. Herzberg, A. Hürstel, J. Iwanicki, D. Jenkins, G. Jones, M. Lewitowicz3, R. Lucas, I. Matea3, F. Negoita, F. de Oliveira Santos3, D. Pantelica, J.A. Pinston5, P. Rahkila, M. Rejmund3, G. Sletten, M. Stanoiu3, C. Timis, R. Wadsworth, J.N. Wilson, M. Zielinska

Shape coexistence in the light krypton isotopes was studied in a series of experiments at GANIL using various experimental techniques. A new low-lying $0^+$ state, a so-called shape isomer, was found in delayed conversion-electron spectroscopy after fragmentation reactions. The systematics of such low-lying $0+^$ states suggests that the ground states of the isotopes $^{78}$Kr and $^{76}$Kr have prolate deformation, while states with prolate and oblate shape are practically degenerate and strongly mixed in $^{74}$Kr, and that the oblate configuration becomes the ground state in $^{72}$Kr. This scenario was tested in experiments performing low-energy Coulomb excitation of radioactive $^{76}$Kr and $^{74}$Kr beams from the SPIRAL facility. Both transitional and diagonal electromagnetic matrix elements were extracted from the observed $\gamma$-ray yields. The results find the prolate shape for the ground-state bands in $^{76}$Kr and $^{74}$Kr and an oblate deformation for the excited $2^{+}_{2}$ state in $^{74}$Kr, confirming the proposed scenario of shape coexistence
1 :  DAPNIA - Département d'Astrophysique, de physique des Particules, de physique Nucléaire et de l'Instrumentation Associée
2 :  CENBG - Centre d'Etudes Nucléaires de Bordeaux Gradignan
3 :  GANIL - Grand Accélérateur National d'Ions Lourds
4 :  IPNL - Institut de Physique Nucléaire de Lyon
5 :  LPSC - Laboratoire de Physique Subatomique et de Cosmologie
6 :  CSNSM - Centre de Spectrométrie Nucléaire et de Spectrométrie de Masse
Physique/Physique Nucléaire Expérimentale
nuclear shape – krypton – nuclei with mass number 59 to 89 – isotopes – nuclear isomerism – deformed nuclei – nuclear fragmentation – electron spectroscopy
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