[Beta] decay of the nucleus ²⁶P at the proton drip line

Abstract

Present thesis reports an experimental study about the beta decay properties of 26P. The excited states of 26Si can be populated by the beta decay of 26P and then deexcited via the emission of protons or gamma rays. In this work, a detection system composed of silicon detectors, Clover-type high-purity germanium detectors and the necessary auxiliary supportive facilities was developed to measure the beta-delayed protons and gamma rays simultaneously, and also perform the proton-proton coincidence measurement. Reliable state information was obtained for the calculation of astrophysical reaction, and proton-proton correlation information was extracted for the investigation of two-proton emission mechanisms. The excited states of 26Si which lie within 500 keV above the proton threshold have very important implications in astrophysical studies, as they are believed to dominant the proton capture reaction rate of 25Al(p,g)26Si in explosive hydrogen burning environments and further influence the synthesis of 26Al in the galaxy. Among these excited states, the one lies at Ex = 5929.4(8) keV [Jp = 3+] has been convinced to make the most contributions to the total reaction rate at the peak temperature of classical novae. This resonant state can be populated by the beta decay of 26P and emit either protons or gamma rays for deexcitation. The beta-delayed protons and gamma rays have been measured in several experiments to investigate the resonant information of Ex = 5929.4(8) keV [Jp = 3+] state, but none of the previous studies observed both of the protons and gamma rays in one experimental setup. Present thesis will report the first simultaneous measurement of the beta-delayed protons and gamma rays that emitted from the Ex = 5929.4(8)keV [Jp = 3+] state. Both the detectors used for the measurement of charged particles and g-rays were calibrated under the same frame, so as to reduce the potential uncertainties caused by the different experimental setups and provide much reliable state property information for the astrophysical calculations. In addition, the isobaric analogue state (IAS) of 26Si populated by the 26P beta decay emits two protons and transits to the ground and first excited states of 24Mg, respectively, which makes 26P a good beta-delayed two-proton (b2p) emitter for the investigation of two-proton emission mechanisms. The detection system employed in this work is suitable for multi-particle emission measurement as the double-sided silicon strip detectors are sensitive both in energy and position for charged particles. Based on the proton-proton coincidence measurement method, the energy and angular correlations of the two protons are reconstructed to investigate the possible two-proton emission mechanisms. Combining the discrete peaks in the individual proton energy spectrum and the opening angle distributions of the two protons, the two-proton branch ending in the 24Mg ground state is determined to be a sequential process via two possible intermediate states of 25Al.