| A.Gorgen, E.Clement, E.Bouchez, A.Chatillon, W.Korten, Y.Le Coz, Ch.Theisen, C.Andreoiu, F.Becker, B.Blank, A.Burger, P.Butler, J.M.Casandjian, W.Catford, T.Czosnyka, P.Davies, S.P.Fox, G.de France, G.Georgiev, J.Gerl, H.Hubel, J.Iwanicki, D.G.Jenkins, F.Johnston-Theasby, P.Joshi, I.Matea, P.Napiorkowski, F.de Oliveira Santos, G.Sletten, C.Timis, R.Wadsworth, 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 {\\it 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. |
