Properties of low-lying intruder states in 34Al and 34Si populated in the beta-decay of 34Mg

The results of the IS530 experiment at ISOLDE revealed new information concerning several nuclei close to the N ≈ 20 'Island of Inversion' - 34Mg, 34Al, 34Si. The half-life of 34Mgwas found to be three times larger than the adopted value (63(1) ms instead of 20(10) ms). The beta-gamma spectroscopy of 34Mgperformed for the first time in this experiment, led to the first experimental level scheme for 34Al, also showing that the full beta strength goes through the predicted 1+ isomer in 34Al[1] and/or excited states that deexcite to it. The subsequent beta-decay of the 1+ isomer in 34Alallowed the observation of new gamma lines in 34Si, (tentatively) associated with low-spin high-energy excited states previously unobserved

Half-life of the yrast 2 + state in 188W: evolution of deformation and collectivity in neutron-rich tungsten isotopes

The half-life of the yrast I π = 2+ state in the neutron-rich nucleus 188W has been measured using fast-timing techniques with the HPGe and LaBr3:Ce array at the National Institute of Physics and Nuclear Engineering, Bucharest. The resulting value of t1/2 = 0.87(12) ns is equivalent to a reduced transition probability of B(E2; 2+ 1 → 0+ 1 ) = 85(12) W.u. for this transition. The B(E2; 2+ 1 → 0+ 1 ) is compared to neighboring tungsten isotopes and nuclei in the Hf, Os, and Pt isotopic chains. Woods-Saxon potential energy surface (PES) calculations have been performed for nuclei in the tungsten isotopic chain and predict prolate deformed minima with rapidly increasing γ softness for 184–192W and an oblate minimum for 194W

Precision Lifetime Measurements Using LaBr

A range of high resolution gamma-ray spectroscopy measurements have been carried out using arrays which include a number of Cerium-doped Lanthanum-Tribromide (LrBr3(Ce)) scintillation detectors used in conjunction with high-resolution hyper-pure germanium detectors. Examples of the spectral and temporal responses of such set-ups, using both standard point radioactive sources 152Eu and 56Co, and in-beam fusionevaporation reaction experiments for precision measurements of nuclear excited states in 34P and 138Ce are presented. The current and future use of such arrays at existing (EURICA at RIKEN) and future (NUSTAR at FAIR) secondary radioactive beam facilities for precision measurements of excited nuclear state lifetimes in the 10 ps to 10 ns regime are also discussed

<i>B </i>(E2;21+→01+) value in ⁹⁰Kr

International audienceA smooth onset of collectivity in Kr-88,Kr-92,Kr-94,Kr-96 has been determined from reported B(E2; 2(1)(+) -> 0(1)(+)) and E(2(1)(+)) values. This is in contrast to the sudden onset in even-even Zr, Mo, and Sr isotopes. Our objective was to complete the systematics by determining the B(E2; 2(1)(+) -> 0(1)(+)) value in Kr-90, which was produced by cold-neutron-induced fission of U-235. The lifetime of the 2(1)(+) state in Kr-90 was measured via the electronic gamma-gamma timing technique using the EXILL and FATIMA spectrometers. Based on themeasured mean lifetime of tau = 15(10) ps, the B(E2; 2(1)(+) -> 0(1)(+)) value of 13(-5)(+26) W.u. in Kr-90 is determined for the first time and the smooth onset of deformation in the even-even Kr isotopes beyond neutron number N = 50 is confirmed

Precision Lifetime Measurements Using LaBr 3

A range of high resolution gamma-ray spectroscopy measurements have been carried out using arrays which include a number of Cerium-doped Lanthanum-Tribromide (LrBr3(Ce)) scintillation detectors used in conjunction with high-resolution hyper-pure germanium detectors. Examples of the spectral and temporal responses of such set-ups, using both standard point radioactive sources 152Eu and 56Co, and in-beam fusionevaporation reaction experiments for precision measurements of nuclear excited states in 34P and 138Ce are presented. The current and future use of such arrays at existing (EURICA at RIKEN) and future (NUSTAR at FAIR) secondary radioactive beam facilities for precision measurements of excited nuclear state lifetimes in the 10 ps to 10 ns regime are also discussed