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Y.X.Luo, J.H.Hamilton, J.O.Rasmussen, A.V.Ramayya, C.Goodin, A.V.Daniel, N.J.Stone, S.J.Zhu, J.K.Hwang, S.H.Liu, C.J.Beyer, Ke Li, H.L.Crowell, D.Almehed, S.Frauendorf, A.Covello0, V.Dimitrov, Jing-ye Zhang, X.L.Che, Z.Jang, D.Fong, A.Gelberg, I.Stefanescu, A.Gargano0, E.F.Jones, P.M.Gore, I.Y.Lee, G.M.Ter-Akopian, Yu.Ts.Oganessian, M.A.Stoyer, R.Donangelo, W.C.Ma, J.D.Cole, J.Kormicki, X.Q.Zhang, S.C.Wu, J.Gilat, T.N.Ginter, S.J.Asztalos0. New Insights into Frontier of Nuclear Structure of Neutronrich Nuclei by Means of Prompt Fission γ Ray Measurements at Gammasphere(II: Section 3 & Section 4)[J]. Nuclear Physics Review, 2010, 27(4): 363-389. DOI: 10.11804/NuclPhysRev.27.04.363
Citation: Y.X.Luo, J.H.Hamilton, J.O.Rasmussen, A.V.Ramayya, C.Goodin, A.V.Daniel, N.J.Stone, S.J.Zhu, J.K.Hwang, S.H.Liu, C.J.Beyer, Ke Li, H.L.Crowell, D.Almehed, S.Frauendorf, A.Covello0, V.Dimitrov, Jing-ye Zhang, X.L.Che, Z.Jang, D.Fong, A.Gelberg, I.Stefanescu, A.Gargano0, E.F.Jones, P.M.Gore, I.Y.Lee, G.M.Ter-Akopian, Yu.Ts.Oganessian, M.A.Stoyer, R.Donangelo, W.C.Ma, J.D.Cole, J.Kormicki, X.Q.Zhang, S.C.Wu, J.Gilat, T.N.Ginter, S.J.Asztalos0. New Insights into Frontier of Nuclear Structure of Neutronrich Nuclei by Means of Prompt Fission γ Ray Measurements at Gammasphere(II: Section 3 & Section 4)[J]. Nuclear Physics Review, 2010, 27(4): 363-389. DOI: 10.11804/NuclPhysRev.27.04.363
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New Insights into Frontier of Nuclear Structure of Neutronrich Nuclei by Means of Prompt Fission γ Ray Measurements at Gammasphere(II: Section 3 & Section 4)

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  • By means of γ-γ-γ and γ-γ(θ) measurements of prompt fission γ rays from 252Cf using Gammasphere, new insights have been gained into the A~100 (Z~40, N>56) neutron rich region, which has long been of interest for shape transitions, shape coexistence and onset of deformations. The systematic investigations of odd-Z isotopes have revealed a shape transition from axially symmetric shapes with very large quadrupole deformations in Z=39 (Y) to near maximum triaxial shapes with moderate quadrupole deformations in Z=43 (Tc), 44 (Ru), 45 (Rh) isotopes. The Nb (Z=41) isotopes are found to be transitional with regard to this shape transition. The bandcrossings observed in the evenN Tc and Rh isotopes are attributed to alignment of a pair of h11/2neutrons. The longexpected sudden shape transition in Nb isotopic chain is now observed. The longsought highspin level scheme and deformed states in 100Nb (N=59) were identified. The ground state of 100Nb was found to be strongly deformed, in disagreement with existing theory. The shape coexistence was confirmed in the nucleus, and the sudden shape transition in the Nb isotopic chain was seen to occur between N=58 (spherical) to N=59 (strongly deformed), in contrast to the sudden shape transition from N=59 (spherical) toN=60 (strongly deformed) in Sr (Z=38), Y (Z=39) and Zr (Z=40) isotopic chains. The observation of strongly deformed ground state in 100Nb and its very large and irregular moments of inertia make 100Nb an especially interesting case for further theoretical studies.
    Recent detailed studies of octupole excitations in odd-Z Cs (Z=55) and La (Z=57) isotopes have discovered a sharp drop in electric dipole moments D0 in the Cs isotopic chain 141, 143, 144Cs, and, most likely, the previously reported moderate drop in D0 in 145, 147La is extended sharply down in 148La. The sharp drops of D0 in Cs and La are most likely analogous to those reported in 146Ba and 224Ra, which were accounted for by the reflectionasymmetric mean field shell correction theory. The very large D0 in both 141Cs and 142Xe and the simplexdependent D0 deduced in 141Cs but not in 143Cs need further theoretical studies. Based on rotational frequency ratios, ω-(I)/ω+(I), octupole vibrations are proposed in Cs isotopes, like the cases in Xe isotopes, while octupole deformations are suggested in La isotopes.
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