RESUMO
Neutron-rich, radioactive Zn isotopes were investigated at the Radioactive Ion Beam facility REX-ISOLDE (CERN) using low-energy Coulomb excitation. The energy of the 2(1)+ state in 78Zn could be firmly established and for the first time the 2+ --> 0(1)+ transition in 80Zn was observed at 1492(1) keV. B(E2,2(1)+ --> 0(1)+) values were extracted for (74,76,78,80)Zn and compared to large scale shell model calculations. With only two protons outside the Z=28 proton core, 80Zn is the lightest N=50 isotone for which spectroscopic information has been obtained to date. Two sets of advanced shell model calculations reproduce the observed B(E2) systematics. The results for N=50 isotones indicate a good N=50 shell closure and a strong Z=28 proton core polarization. The new results serve as benchmarks to establish theoretical models, predicting the nuclear properties of the doubly magic nucleus 78Ni.
RESUMO
The reduced transition probabilities B(E2;0(+) --> 2(+)(1)) of the neutron-rich (74)Zn and (70)Ni nuclei have been measured by Coulomb excitation in a (208)Pb target at intermediate energy. These nuclei have been produced at Grand Accélérateur National d'Ions Lourds via interactions of a 60A MeV (76)Ge beam with a Be target. The B(E2) value for (70)Ni(42) is unexpectedly large, which indicates that neutrons added above N=40 strongly polarize the Z=28 proton core. In the Zn isotopic chain, the steep rise of B(E2) values beyond N=40 continues up to (74)Zn(44). The enhanced proton core polarization in (70)Ni is attributed to the monopole interaction between the neutron in the g(9/2) and protons in the f(7/2) and f(5/2) spin-orbit partner orbitals. This interaction could result in a weakening of magicity in (78)Ni(50).
RESUMO
To analyse the origins of the appearance of the zoonite concept as a unit of segmentary organisation in zoology requires positioning oneself in the context of the first half of the nineteenth century, more specifically in the years 1826-1839. If the origins of the problem go back to Goethe, on the one hand, and to botanists such as de Candolle on the other, the thesis of Moquin-Tandon on the splitting of plants (1826) is an essential step. The hypotheses of multiplication and diversification of organs arranged according to a symmetry, also presides over his research on the Hirudinées (1827). The zoonite is an elementary organic unit which can multiple itself and is structured symmetrically. But what characterises it is that its composition confers on it a certain autonomy. In 1832, Dugès regarded the connection between zoonite and total organism from the angle of organic conformity. He deduced from his observations the laws of multiplicity of organisms, of disposition, of modification and of coalescence. This last law would become vital to Dugès in 1838 for explaining the evolution of the composed being as well as embryonic development. But zoonitism in the 1830s did not constitute a scientific theory, even if it would ultimately serve as a reference, in particular for the animal physiology of Edwards.