Beta-decay studies of high-isospin nuclei ³¹Ar, ³³Ar and ⁴¹Ti

Abstract

This thesis is a review of five different articles already published or submitted for publication. Beta decay properties of proton-rich isotopes of ³¹Ar, ³³Ar and ⁴¹Ti were surveyed experimentally. In addition, the mechanism of beta-delayed two-proton emission was studied in the decay of ³¹Ar. Two types of on-line mass separators were applied to select and transport the studied nuclei. The detection of delayed radiation was done by means of silicon, gas, germanium and scintillation detectors. A special construction of a gas-silicon detector telescope was developed for these studies. In comparison with conventional silicon telescopes the new telescope proves to be progressive. It allows detection of charged particles with better energy resolution and reduced detection threshold. All the studied nuclei are beta-delayed proton precursors. They possess high beta-decay energies, which allowed measurement of beta-decay strength up to 8 MeV excitation in ⁴¹Sc and 14 MeV in ³¹Cl. Fifteen new energy levels were discovered in ³¹Cl. Isospin impurity in the lowest Jπ=3/2⁺, T=3/2 level in ⁴¹Sc was deduced to be ≈10%. Partial decay widths for proton emission were studied for ³³Ar. Comparison of experimental results to output of the shell model calculations showed the generally acknowledged problems, such as, quenching of the beta strength and scarcity in predicting level energies. A conclusion cannot be given for the mechanism of 2p-emission in the decay of ³¹Ar.