G. Walter

Study of the giant gamow-teller resonance in nuclear β-decay: The case of 32Ar

Delayed proton and gamma emissions following the β-decay of 32Ar have been studied. The half-life of 32Ar is 98 ± 2 ms, and the T = 2 analogue state in 32Cl lies at the excitation energy 5036 ± 12 keV. From the intensity of the feeding to this state the proton intensities can be converted to an absolute scale leading to a total proton branching ratio of (43 ± 3)%. From proton-gamma coincidence measurements it emerges that (1.9 ± 0.2)% of the protons lead to the first-excited state in 31S. A level scheme up to 8.75 MeV excitation in 32Cl has been constructed and the Gamow-Teller strength function has been deduced. The result is a renormalization of the axial-vector strength to (49 ± 5)% of the free-nucleon value.

Single-neutron states in Sn-133

The location of several single-neutron states in Sn-133 has been identified. The P-3/2, h(9/2), and f(5/2) states were found at 853.7, 1560.9, and 2004.6 keV, respectively, by measuring gamma rays in coincidence with delayed neutrons following the decay o

34Si: A new doubly magic nucleus?

Abstract The 34 Al β-decay was studied at the CERN on-line mass separator ISOLDE. A 34 Al β-decay scheme to 34 Si bound states is established. The first level scheme in 34 Si including three levels at 3328, 4257 and 4383 keV with respectively J π =2 + , 3 − and (4, 5) − , is consistent with a J π =4 − assignment for the 34 Al ground state. The value of P 1 n =0.27 (5) is deduced. The 34 Si level scheme is in agreement with the present shell-model predictions and 34 Si appears as a doubly magic nucleus.

Level structure of light even xenon nuclei populated in the decays of isomeric and ground states of 118,120,122Cs

Abstract Gamma and conversion electron lines following the β-decay of 118,120,122Cs nuclei have been investigated at the ISOLDE facility. Evidence has been found for two isomeric states with similar half-lives in 118,120Cs. Level schemes of 118,120,122Xe including levels of the quasiground state, gamma and beta bands have been established. The structure of these nucle is discussed in the framework of the rotational model and the vibrational limit of the interacting boson approximation (IBA) approach.

The levels of 185Ir populated in the decay of 185m + gPt

Abstract The decay scheme of 185m + g pt has been investigated using isotopically separated samples produced by the ISOLDE facility. A level scheme of 185 Ir has been established. The 3 2 + [402] and 1 2 + [400] positive parity bands have been observed. The negative parity levels belonging to the h 9 2 and h 11 2 orbitals are discussed in the framework of the asymmetric rotor-plus-particle model.

Isolde ps booster facility at cern: Experiments with slow radioactive beams

Abstract CERNs ISOLDE, an acronym for Isotope Separator On Line, went into operation again last year, after a major upgrading that has placed the facility in new building complex fed by a 1 GeV proton beam from the injector synchrotron, called the PS Booster (PSB). Hence, ISOLDE is now firmly integrated into the accelerator architecture of CERN. In the following, we give a description of the new installation and the physics that is being studied there. As is more often than not the case with laboratory visits and “portraits,” the picture is kaleidoscopic, and we have tried to make the overview easier by placing most of the examples and all the detailed information in the form of “Panels,” most of them illustrated and all of them, we hope, sufficiently self contained, so that they can be read without referring to the main text and to other Panels. For a start we point to Panel I, which gives some important dates and data concerning ISOLDE.

The 49K beta decay

Abstract The decay of 49 K has been studied using a mass-separated ion beam by neutron and gamma-ray singles and multiparameter spectroscopic measurements. The 49 K activity was produced by 600 MeV proton fragmentation reactions in a uranium target. The observed beta-strength function displays two resonances centered at about 6.5 MeV and 9.5 MeV in 49 Ca. This structure is discussed in simple shell-model terms.

Laser ionization in β decay studies of Zn and Mn nuclei

Resonance ionization laser ion source (RILIS) technique has been used in the β-decay studies of 59Mn and 58Zn. The importance of the RILIS for production of these elements is discussed. The properties of the low-lying levels of the studied nuclei are discussed.

Décroissance β de 40Cl

Abstract The γ-rays following the β − decay of 40 Cl have been investigated with Ge(Li) and Nal(Tl) detectors. The 40 Cl sources were produced by fast-neutron bombardment of high-purity liquid argon samples. The half-life was measured to be 1.32 ± 0.02 min. Coincidence data for the prominent lines lead to a decay scheme accounting for 71 transitions, out of the 76 attributed to 40 Ar, between 37 levels. The 40 Cl β-ray branching was inferred from the relative γ-ray intensities. Evidence is found for 22 new β-branches. A previously reported strong β-group (20 %) to the first excited state is shown to have an intensity ft values support J π = 2 − for the ground state of 40 Cl.

Beta-decay of 56Cu

Abstract By measuring positrons and β -delayed γ -rays emitted from mass-separated sources, the decay of 56 Cu (4 + , T z =−1, T =1) to states in the doubly-magic nucleus 56 Ni was studied for the first time. The half-life of 56 Cu was measured to be 78(15) ms, and four β -delayed γ -rays were assigned to its decay. The resulting experimental data on Fermi and Gamow–Teller strength are compared with shell-model predictions.