NUCLEI WITH ODD MASS NUMBER A AND CHARGE NUMBER Z IN THE REGION WHERE A IS NEAR 190 (in French)
For nuclei in which the number of neutrons is 88 to 90 (A is approximately 150), a sharp variation of their properties is produced: the energy of the collective excited level and the Coulomb excitation cross section vary. This discontinuity indicates the passage from the almost spherical form to the ellipsoidal form. The possible existence of the inverse passage in the region of the magic number Z = 82 and N -- 126 was studied. The energy levels of three nuclei in the region of A = 190: Ir/sup 191/, Ir/sup 193/, and Au/sup 197/ were measured. First, the definition of the characteristic nuclear magnitudes necessary for the comprehension of the study and the expressions resulting from the shell model and the unified Bohr-Mottelson-Nilsson model are reviewed. The decay of Os/sup 191/ was studied to determine the maximum energy and complexity of the beta /sup -/ spectrum, the K/L ratio and conversion coefficient of the 129-kev photon, and the nature of 42-kev photon. The decay of Os/sup 193/ was studied to explain the disagreement between the configuration of the g/sub 7/2/ level and the shell and unified models and to define the nature of the 558-kev photon. A direct measurement of the conversion coefficient of the 191-kev photon in the decay of Hg/sup 197/ was made. A coherent scheme of the excited levels of Ir/sup 193/ was established. The examination of the systematics of nuclei with mass number approxtmately 190 showed that the configuration of the ground level and first excited 1/2 level of Ir and Au nuclei can be interpreted with the shell model. The unified model takes into account the shape of the energy variation of the 11/2-- and 1/2+ levels and the filling of the h/sub 11/2/ level for Au and Ir nuclei. The transition probabilities measured were in excellent agreement with the theoretical calculations based on the Nilsson wave functions. In its collective aspect the unified model permits the conclusion that the inertia moments of rotation families based on the ground level presents a sharp discontinuity during the passage from Ir to Au, corresponding to the filling of the h/sub 11/2/ level. The energy of the first excited level of rotation fandlies based on 1/2 particle level is compatible with a decoupling factor in excellent agreement, for Re/sup 185/, Ir/sup 191/, Ir/sup 193/, Au/sup 193/, Au/ sup 195/, and A u/sup 197/, with the theoretical predictions of Nilsson. The discontinuity observed in deformation of nuclei during the passage from Ir to Au does not introduce a sharp variation of the intrinsic structure or of the characteristic nuclear magnitudes. It appears that for nuclei passing from Re (deformed nuclei) to Au (almost spherical nuclei) the unified model only can give a coherent interpretation of experimental data. (J.S.R.)
- Research Organization:
- Universite, Paris
- NSA Number:
- NSA-14-012212
- OSTI ID:
- 4195114
- Journal Information:
- Ann. phys., Vol. Vol: (13) 5; Other Information: Orig. Receipt Date: 31-DEC-60
- Country of Publication:
- Country unknown/Code not available
- Language:
- French
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Related Subjects
ATOMS- BETA DECAY- BRANCHING RATIO- CAPTURE- COULOMB EXCITATION- CROSS SECTIONS- DECAY- DEFORMATION- ELECTRIC CHARGES- ELECTRONS- ENERGY- ENERGY LEVELS- EXCITATION- GOLD 193- GOLD 195- HALF-LIFE- - INTERNAL CONVERSION- IRIDIUM 191- MASS- MASS NUMBER- MEASURED VALUES- NILSSON MODEL- NUCLEAR MODELS- NUCLEAR STRUCTURE- NUCLEAR THEORY- NUCLEI- OSMIUM 191- PARITY- PHOTONS- QUANTUM MECHANICS- RARE EARTHS- RHENIUM 185- ROTATION- SHELL MODELS- SPECTRA- SPHERES- SPIN- VARIATIONS
ATOMS- CONFIGURATION- COULOMB EXCITATION- CROSS SECTIONS- DECAY- DEFORMATION- ELECTRIC CHARGES- ENERGY- ENERGY LEVELS- EXCITATION