Göttingen 1997 – wissenschaftliches Programm

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HK: Hadronen und Kerne

HK 42: Kernspektroskopie, mittelschwere Kerne II

HK 42.2: Gruppenbericht

Mittwoch, 26. März 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 πg_9/2→νg_7/2 (A∼100) and πh_11/2→νh_9/2 (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.