J. Genevey

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.

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).

Level structures of 119,121Xe excited in (12C, 3nγ) reactions and analysis of the h112 bands in the IBF model

Abstract Levels in 119, 121 Xe excited by the reactions 110, 112 Cd( 12 C, 3nγ) 119, 121 Xe have been studied by in-beam γ-ray spectroscopic techniques. Several bands have been observed: h 11 2 and g 7 2 in 119, 121 Xe , a decoupled one in 121 Xe. A new level structure in 119 Xe found for the first time is assigned as the g 9 2 band generated by one hole in the g 9 2 neutron shell. The connections between these bands have been fixed in both nuclei. A detailed analysis is made for the h 11 2 level structure. An interpretation is given in terms of the interacting boson-fermion model where h 11 2 , f 7 2 and h 9 2 fermion configurations are included.

Mass, charge, angular and energy distributions in the interaction of 84 MeV/A12C with silver and tin

The cross sections, the angular distributions and the ranges of the target fragmentation products formed by the reaction of 84 MeV/A12c with natural silver and tin have been evaluated. Their identification has been made by offline gamma ray decay measurements.

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.

High-spin states in the odd-odd nucleus 49108In

Abstract Levels in 108 In were studied using the 98 Mo( 14 N, 4nγ) 108 In reaction at 65 MeV. The experiments included γ-ray yields as a function of bombardment energy, γ-γ coincidence measurements, γ-ray angular distributions, γ-ray linear polarization and conversion electron measurements, γ-ray intensities were also extracted from the 108 Cd( 3 He, p2nγ) 108 In reaction at 40 MeV. The 108 In level scheme exhibits a simple structure including only 13 levels. The main feature consists of ΔI = 1 transitions based on the 1119.3 keV level (7 − ) and the 2514.3 keV level (9 − ). However no ΔI = 2 transition was observed. The lower band is interpreted in the frame of the rotor + two-quasiparticle model.

Identification and decay of102In, new neutron deficient isotope close to100Sn

Abstract102In, [T1/2=(24±4)s], has been identified for the first time using an on-line mass isotopic separator operating on nuclear reactions induced by heavy ions. Gamma-rays observed both in102In→102Cd decay and in-beam measurements allow to build a partial level scheme for102Cd. Systematics of the two first excited states of even cadmium isotopes shows the special behaviour of the lightest one.

On the nature of the 17 μs isomer of the 133Sb valence nucleus

Abstract: The decay of the 17 μs isomer of 133Sb was re-investigated experimentally. It was produced by thermal neutron induced fission of 241Pu. Its detection is based on time correlation between fission fragments selected by the LOHENGRIN spectrometer at ILL (Grenoble), and the γ-rays, and conversion electrons from the isomer. The interpretation of the level scheme is based on shell model calculations, where empirical two-body matrix elements were employed. The good agreement between theory and experiment suggests that the isomer is the 21/2+ member of the 2p-1h πg7/2ν(f7/2h11/2−1) configuration.

Low-lying states in the doubly odd nucleus 132Pr from beta decay of 132Nd

Abstract The low-lying level scheme of the odd-odd nucleus 132Pr has been investigated for the first time. The radioactive nuclei were produced by bombarding 96Mo targets with a 225 MeV 40Ca beam. Levels in 132Pr have been populated from the 132Nd β-decay. A new value of its half-life has been measured: T 1 2 = 88 ± 7 s . The activities produced in the reaction have been transported with a He-jet device and γγt, Xγt, e−γt coincidence measurements performed. Internal conversion coefficients have been measured with a magnetic lens spectrometer. The experimental level scheme of 132Pr is compared to theoretical calculations performed with the interacting boson-fermion-fermion model (IBFFM).

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.