A. Gizon

New insight in the level structure of 153Er

Abstract: The high-spin level structure of the 153Er nucleus has been reinvestigated by in-beam γ-ray and electron spectroscopy with (14N,pxn) reaction. Excitation energies, spin and parity assignments are unambiguously established for the two lowest isomers T1/2≃ 380 ns and T1/2\simeq 10 ns. The characteristics of the third one (T1/2≃ 250 ns) at 5.2 MeV are still questionable but its main decay modes are better known. An extension of the level scheme is proposed up to 8.4 MeV.Experimental results have been discussed in terms of shell model multiplets and compared with the other structures observed in N=85 neighbouring nuclei.

La Désintégration 109Cd→109Ag

Abstract The 88 keV transition in 109 Ag has been studied by means of a double-focussing magnetic β-spectrometer and of a solid-state Ge(Li) detector. By comparison with the 84 keV transition in 170 Yb, the energy was found to be 88.09±0.03 keV and the internal conversion coefficient α K =12.7±0.9. The internal conversion spectrum has been recorded. All internal conversion measurements agree very well with a pure E3 assignment and theory. The fluorescence yield deduced from the Auger spectrum is ω K =0.834±0.018.

Identification and structure of yrast levels in theN=89 odd-odd158Tm nucleus

Excited levels have been identified in the odd-odd158Tm nucleus produced in the150Sm (14N,6n) reaction. The observed level structure based on an isomeric state (T1/216±4 ns) is interpreted as a rotational aligned band.

Detailed spectroscopy of the normally deformed states in 132Ce

Abstract High-spin states have been studied in 132 Ce produced in the 100 Mo( 36 S,4nγ) reaction using the EUROGAM II spectrometer. The structure of the normally deformed states ( β 2 ∼ 0.2) has been investigated. Eight ΔI = 2 bands and three ΔI = 1 bands have been identified and the level scheme extended up to spin and parity (40 + ) at an excitation energy 19.79 MeV. The results are interpreted with the aid of Woods-Saxon cranking calculations, which suggest a variety of triaxial (γ) shapes in this nucleus stabilised by specific active quasiparticle orbitals.

Level structures of 131,129Ce observed in beta decay

Abstract The low-lying levels of the odd-mass nuclei 131 Ce and 129 Ce have been investigated by means of the β + EC decays of 131g+m Pr and 129 Pr, respectively, The Pr nuclei were obtained by bombarding 94,96 Mo targets with a 255 MeV 40 Ca beam. The radioactivities produced in the reactions were transported with a He-jet device and γγt , X γt , e − γt coincidence measurements were performed. Conversion electrons were measured with a magnetic spectrometer and transition multipolarities were deduced. On-line mass separation was used to select the 129 Pr β-decay. The resulting level schemes of 131,129,127 Ce are discussed in connection with level systematics and calculations performed by using the Interacting Boson-Fermion Model (IBFM).

Evidence for multiple band terminations in 102Pd

Abstract The level structure of 102 Pd has been investigated using data collected with the Eurogam 2 array. Several cascades of γ-rays have been established up to high spins. Termination of rotational bands has been observed at I π = 28 − and 32 + , and tentatively at I π = 38 + and 42 + . The nucleus 102 Pd is the first case where rotational bands built on valence space configurations are followed from spin close to zero up to termination and, at higher spins, a smooth rotational band which appears to terminate is built on core excited configurations.

Collective excitations in 106Cd

High Spin states in 106Cd were populated by the reactions Zr-94(O-17, 5n) and Ge(S-32, 4n) at 80 MeV and at 148 MeV, respectively. The gamma-decay was studied by gamma-spectroscopic methods using t ...

ISOMERIC M3 TRANSITIONS IN 183PT AND 181OS

Abstract The M3 transitions linking the ν 7 2 [514] and ν 1 2 [521] states in 78183Pt105 and 76181Os105 have been searched by high-resolution conversion-electron measurements. The reduced M3 transition probabilities have been estimated and compared to the values obtained in neighbouring isotones (74179W105 and 79184Au105). All the known M3 transitions are presented and their properties discussed, especially as a function of deformation. The present work supports the π h 9 2 ⊗ν 1 2 [521] and π h 9 2 ⊗ν 7 2 [514] particle configuration assignments proposed for the 184Au isomeric and ground states, respectively.

Quasi-compound nucleus formation with 84 MeV/N12C projectiles

Angular and mass distributions of heavy fragments have been measured in nuclear reactions induced by 84 MeV/N12c on natAg, 112, 118, 124Sn. Products observed at small angles, with masses around 50, exhibit 1 MeV/N energies. A quasi-compound nucleus formation followed by evaporation is proposed as a possible explanation.

Spin and parity of isomeric and ground states of the doubly-odd nucleus184Au

Low-spin states in doubly-odd184Au have been populated in the β+/EC decay of184Hg produced by bombarding184Sm targets with an 185 MeV40Ar beam. Radioactive Hg nuclei were transported by a He jet system. A new level scheme has been established from γ-γ-t and X-γ-t coincidence measurements. Spin and parity values Iπ=5+, Iπ =2+ and Iπ=3− were assigned to the ground state and the two isomeric states of184Au, respectively. The structure of these states is discussed using B(E1) values.