R. Duffait

Lifetimes and structures of some levels above 1.5 MeV in 168Yb, 164Er and 158, 160, 162Dy

Abstract The following lifetime measurements have been performed in 168 Yb: 62 ns (7 − , 2222.5 keV), 0.34ns (6 − , 2111.1 keV), 81.7 ns (5 − , 1998.7 keV), ≦ 0.14 ns (4 + , 2203.8 keV); in 164 Er: 23.3 ns (7 − , 1985.0 keV), 0.22 ns (6 − , 1744.4 keV), ≦ 0.08 ns (5 − , 1664.2 keV); in 158 Dy: ≦ 0.11 ns (4 + , 1895.3 keV); in 160 Dy: 0.18 ns (4 + , 1694.0 keV); in 162 Dy: 1.93 ns (5 − , 1485.9 keV). The experimental reduced transition probabilities are discussed in the framework of current nuclear models.

Connection of a He-jet to the medium-current source of the SARA on-line separator

Abstract The performances of a Bernas-Nier ion source coupled to a helium-jet transport system are reported. The results of coupling efficiency measurements using various cluster materials are given for a number of elements, especially of the light rare-earth region reached through heavy-ion (HI) fusion-evaporation reactions at SARA. The identification and study of several new neutron-deficient isotopes investigated using this system are presented.

High spin states and multiquasiparticle excitations in odd-odd114, 116Sb nuclei

Excited states of114, 116Sb have been investigated in the111, 113Cd (7Li, 4nγ) reactions. In both level schemes, two independant parts have been exhibited with, mainly, a negative parity band based on 8− or 7− states and a positive parity sequence based on a 11+ state. The interpretation of the significant levels has been performed in the core-particle model and in term of quasiparticle configurations mixing, this last approach being able to give a kind of unified description of the whole spectrum.

The decay of 80s 156Tm

Abstract The level structure of the 88-neutron nucleus 156 88 Er has been investigated from the EC and β + decay of 156 Tm (T 1 2 = 80 s ) . Mass-separated samples were obtained from the Orsay on-line separator. Gamma-ray spectra, conversion electron spectra, and γ-γ bi-dimensional coincidences were performed by using semiconductor detectors. Members of the β- and γ-bands are proposed. The possible superposition of the 0 + β-level and the 2 + γ-level at 930.5 keV is discussed.

Identification and decay of 12s138Eu

A 12 s138Eu. activity different from previously reported 1.5 s and 35 s isomers has been identified in the35Cl+Cd reaction products at 191 MeV energy using a He-jet coupled to a mass separator. The decay scheme derived from γ-γ coincidence measurements account s for probable spin and parity of 7+ for138Eu.

Gamma-ray doppler shift measurements in 93Mo

Abstract The lifetimes of a number of levels in 93Mo have been measured with the Doppler shift attenuation method (DSAM) using the 93Nb(p, nγ)93Mo reaction and observing the γ-rays emitted by the 93Mo nuclei recoiling in the self-supporting 93Nb target. The lifetimes are: 115−45+60 fs, 1362.95keV; 340−130+180 fs, 1477.15keV; 38−13+20 fs, 1492.30 fs; > 280 fs, 1520.28 keV; 95−25+50 fs, 1694.50 keV; 205−65+100 fs, 2141.10 keV; > 390 fs, 2246.80 keV; > 290 fs, 2303.90 keV; > 500 fs, 2355.25 keV; > 900 fs, 2409.00 keV; 160−55+90 fs, 2430.90 keV; > 440 fs, 2440.20 keV; 87−30+50 fs, 2479.00 keV; 130−35+60 fs, 2535.20 keV. The results are compared to previous experimental or theoretical investigations.

New exotic neutron-deficient nuclei nearN=82

Residual activities produced via35Cl or32S beams in thin112Sn and106Cd targets have been studied by γ-ray and X-ray spectroscopy techniques behind a He-jet system. Mass identification of the products has been performed by coupling the He-jet to the medium current ion source of an isotope separator. Neutron-deficient nuclei with 137≦A≦144 have been identified. Decay schemes of several new isotopes as138Eu (12s),141Gd (22s),143Tb (12s and <17s),144Dy (9s) and possibly140Gd (11s) have been derived. New informations have also been provided for137Sm (45s),139Eu (24s) and144Tb (5s). Data have been presented through systematics. The shapes of these nuclei and their trends versusN andZ have been analysed.

On-line γ-ray investigation of the14N+27Al reaction at 30 MeV/u

The cross-sections of target-like residues following the14N+27Al reaction at 30 MeV/u have been measured from in-beam and radioactiveγ-ray spectra. The recoil velocities of some fragments have been estimated from theγ-ray Doppler broadening.