Göttingen 1997 – scientific programme
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HK: Hadronen und Kerne
HK 42: Kernspektroskopie, mittelschwere Kerne II
HK 42.2: Group Report
Wednesday, March 26, 1997, 14:30–15:00, HS E
High-resolution and high-efficiency Gamow-Teller β-decay studies around 100Sn and 146Gd — •R. Collatz1, J. Agramunt2, A. Algora3, L. Batist4, D. Cano-Ott2, A. Gadea5, M. Gierlik6, H. Grawe1, M. Hellström1, Z. Hu1, M. Karny6, R. Kirchner1, P. Kleinheinz7, O. Klepper1, A. Plochocki6, E. Roeckl1, B. Rubio2, J. Saarinen1, M. Shibata1, J. Szerypo6, J.L. Tain2, and EBGSI8 — 1GSI, Darmstadt, Germany — 2IFIC Valencia, Spain — 3INR, Derbecen, Hungary — 4NPI, Gatchina, Russia — 5INFN Legnaro, Italy — 6University of Warsaw, Poland — 7KFA Jülich, Germany — 8
The reliable determination of the Gamow-Teller (GT) strength from β-decay in heavy nuclei is usually limited by the finite detection sensitivity for γ-rays. Particularly at high excitation energy in the daughter nucleus, when the Fermi function becomes small, the non-observation of β-feed has drastic consequences on the GT transition rates. To solve this problem, extensive GT β-decay investigations were started recently at the on-line mass separator of GSI Darmstadt using two complementary experimental techniques. First, a large volume NaI detector for total γ-ray absorption was installed and β-decay studies of light indium isotopes and odd-odd N=83 nuclei above 146Gd were carried out. This Total Absorption Spectrometer (TAS) with its high efficiency is in principle sensitive to weak β-branches which remain unobserved with conventional Ge detectors. Therefore, this spectrometer should allow to detect the entire GT strength. However, precise knowledge on the response function and reliable data on the γ-decay pattern are mandatory to deconvolute the raw spectra. Thus, a complementary experiment was performed utilizing six Euroball Cluster detectors in close geometry (Ω=65%) to obtain high-resolution β-decay results of sofar unknown sensitivity. In 40Ca and 58Ni incuced fusion-evaporation reactions the β-decays of 97Ag50, 98Ag51, 102In53, 147Dy81, 148Tb83, 150Ho83, and 152Tm83 were studied. These decays are governed by the fast GT transitions πg9/2→νg7/2 (A∼100) and πh11/2→νh9/2 (A∼146), respectively. In total, ∼500 GByte of γγ-coincidences and γ-singles events were recorded. The data clearly reveal intense high-lying GT resonances in the respective daughter nucleus. First examples of these unique experimental results will be presented.