First measurement of beta-decay half-lives and neutron emission probabilities in several isotopes beyond N = 126

• Autores: Roger Caballero Folch
• Directores de la Tesis: Guillem Cortes Rossell (dir. tes.), César Domingo Pardo (dir. tes.)
• Lectura: En la Universitat Politècnica de Catalunya (UPC) ( España ) en 2015
• Idioma: inglés
• Tribunal Calificador de la Tesis: José Luis Taín (presid.), Francisco Calviño Tavares (secret.), Zsolt Podolyak (voc.)
• Materias:
  • Física
    • Física atómica y nuclear
      • Reacción nuclear y dispersión
      • Estructura nuclear
    • Nucleónica
      • Detectores de partículas
• Enlaces
  • Tesis en acceso abierto en: TDX
• Resumen

  • In this work beta-decay half-lives and neutron-emission probability values have been experimentally determined for first time in several nuclei beyond the neutron-shell closure at N=126. To this aim the accelerator complex at the GSI center for heavy ion research (Germany), in combination with the FRS fragment separator, were employed. The beta-decay detection system consisted of a charged particle detector named SIMBA, which served to detect both ion and beta-particles, surrounded by an array of He-3 based neutron counters named BELEN. The half-life values of eighteen isotopes of Au, Hg, Tl, Pb and Bi were determined, as well as the neutron-branching ratios (or upper limits) for seven nuclei. A comparison of the present results with previous half-life measurements in this mass-region shows a generally good agreement, thus reflecting the systematic validity of the decay data available in this region. Compared to theoretical models, our results show a reasonable agreement for half of the analyzed isotopes, and large discrepancies of up to a factor of 10 for the other half. The measured neutron-branching ratios represent the first set of experimental data available in this mass-region for several isotopes. Owing to the absence of previous experimental results, the values reported here can be only compared with theoretical predictions. In summary, a fair compatibility is found between FRDM+QRPA calculations, which however are underestimating by a factor of 5 the neutron-branching ratio of Tl-215, which is the most exotic nucleus measured in this work.