A. Gadea

Pulse pileup correction of large NaI(Tl) total absorption spectra using the true pulse shape

Abstract The usefulness of a simple numerical correction method of electronic pulse pileup distortion in measured energy spectra is investigated. The algorithm only requires the knowledge of the true pulse shape. The accuracy of the correction achieved for total absorption gamma-ray spectroscopy measurements with NaI(Tl) detectors is demonstrated.

Delayed g9/2 Alignment in the N=Z Nucleus 72Kr

The structure of Kr-72 has been investigated at GASP through the Ca-40(Ca-40,2 alpha) reaction at a beam energy of 160 MeV using the 4 pi ISIS Si-ball for reaction channel selection. The level scheme has been extended up to an excitation energy of approximate to 8.5 MeV. The spins and parities of the observed levels are assigned tentatively. The observed band shows the predicted change from oblate to prolate shape. The four quasi-particle g(9/2) alignment is found to be significantly delayed in rotational frequency with respect to the heavier Kr isotopes. Such a delay contradicts the predictions of standard mean-field calculations and may reflect either additional correlations in the T = 0 pairing channel or coupling to vibrational degrees of freedom or both

Monte Carlo simulation of the response of a large NaI(Tl)total absorption spectrometer for β-decay studies

Abstract The response of a large NaI(Tl) total absorption spectrometer for β-decay studies is investigated.The accuracy of Monte Carlo simulations taking into account the light yield non-proportionality of NaI(Tl) and the detailed geometry is assessed through comparison with spectra measured for several radioactive sources.

Simulation of light collection in scintillators with rough surfaces

Abstract A simple model to evaluate the light collection in scintillators with rough surfaces by Monte Carlo simulation is proposed. The model has a single parameter related to the degree of roughness. The results are compared with measurements for a long tapered BGO crystal.

Spectroscopy of neutron-rich Dy-168,Dy-170: Yrast band evolution close to the NpNn valence maximum

The yrast sequence of the neutron-rich dysprosium isotope Dy-168 has been studied using multinucleon transfer reactions following collisions between a 460-MeV Se-82 beam and an Er-170 target. The reaction products were identified using the PRISMA magnetic spectrometer and the gamma rays detected using the CLARA HPGe-detector array. The 2(+) and 4(+) members of the previously measured ground-state rotational band of Dy-168 have been confirmed and the yrast band extended up to 10(+). A tentative candidate for the 4(+) -> 2(+) transition in Dy-170 was also identified. The data on these nuclei and on the lighter even-even dysprosium isotopes are interpreted in terms of total Routhian surface calculations and the evolution of collectivity in the vicinity of the proton-neutron valence product maximum is discussed. (Less)

Beta decay of 103In: Evidence for the Gamow-Teller resonance near 100Sn

Abstract The β decay of the neutron-deficient isotope 103 In was investigated by using total absorption γ-ray spectrometry on mass-separated sources. The measurement reveals a high-lying resonance of the β-decay strength in striking disagreement with high-resolution γ-ray data. The result is discussed in comparison with shell-model predictions.

Gamow–Teller strength distribution near 100Sn. The beta decay of 102In

One of the main motivations of today’s β-decay studies is to investigate whether the presence of many bound nucleons affects the value of the Gamow—Teller (GT) axialvector coupling constant. The quest for 100Sn is driven by the hope that its particulary simple decay scheme may help to perform improved tests of the models used to calculate the summed GT strength (B GT). Since 100Sn can not yet be produced in sufficient quantity, the experiments are restricted to nearby nuclei. In this paper we report on a study of the β decay of 102In, performed at the GSI Online Mass Separator. This odd—odd nucleus has a very complicated decay scheme and thus represents indeed a great challenge. The loss of numerous weak transitions in high resolution mesurements is suspected to be one of the main reasons for incomplete B GT measurements. Therefore, the experiment with a cube-like array of 6 Euroball Cluster high-resolution germanium detectors (Euroball Cube), with 7 crystals per Cluster, was complemented by the measurement with a total-absorption gamma spectrometer (TAS) [1].

Production of very neutron-deficient isotopes near 100Sn via reactions involving light-particle and cluster emission

Abstract The production of very neutron-deficient isotopes near 100Sn has been investigated by using on-line mass separation of evaporation residues produced by heavy-ion induced complete-fusion reactions. We measured the cross sections for 99Cd, 100In, 101Sn and 102In via 58Ni+58Ni fusion reactions followed by cluster emission, and via 58Ni+50Cr fusion reactions accompanied by evaporation of protons, neutrons or α particles. Both types of reactions yield similar cross sections for the production of exotic nuclei near 100Sn. The data are discussed in comparison with results obtained from statistical-model calculations.

Determination of the Gamow–Teller strength function for the neutron-deficient isotopes 104–107In

Abstract The Gamow–Teller β decays of the neutron-deficient indium isotopes 104–107 In have been investigated by using total absorption γ -ray spectrometry on mass-separated sources. The experimental Gamow–Teller strength, deduced as a function of the excitation energy in the daughter nuclei 104–107 Cd, is compared to shell-model predictions.

Very high rotational frequencies and band termination in 73Br

Rotational bands in