Nuclear structure investigations using gamma-ray and electron spectroscopy

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The building blocks of the world around us are atoms which are formed of a cloud of electrons orbiting a tiny, very dense core called the nucleus. This nucleus is formed of a collection of protons and neutrons. It is the aim of this research to help further our understanding of the interactions between the protons and neutrons within the nucleus. Inside a nucleus the protons tend to pair up with each other, and the neutrons also form pairs, in both cases with their spin quantum numbers coupled to zero. This is somewhat analogous to the electron pairs (Cooper pairs) in a superfluid. It is then the interaction between these pairs and the breaking of individual pairs which are the excitations we can observe in the laboratory. In the special case of nuclei with the same number of neutrons and protons, so called N=Z nuclei, another situation arrises where neutron-proton pairs can form. This special type of pair can couple the spins not just to zero but also to one and still obey the rules of quantum mechanics. The unique properties of these neutron-proton pairs and how similar they behave to the usual neutron-neutron or proton-proton pairs is still not fully understood. In the proposed research here we will produce a high energy beam of a N=Z nucleus at the ISAC facility of TRIUMF, Vancouver. This high energy beam will then undergo a nuclear reaction to form a hot, excited state. The TIGRESS detector will be used to observe the high energy form of light, called gamma rays, which are emitted as the nucleus cools down again after the reaction. In some special cases the nucleus cools down not by emitting a gamma ray but by emitting an atomic electron. The new SPICE spectrometer will be able to detect these electrons which can provide additional information to the gamma rays alone. In studying the energy and properties of the gamma rays or electrons we can investigate the interactions between the neutrons and protons inside the nucleus.