Cluster structure in nuclei and nucleosynthesis process in the universe

In studying the cluster structure in nuclei, the measurement of monopole excitation intensity via alpha inelastic scattering is effective. This paper described the alpha condensed state in self-conjugated A=4n nuclei and the cluster state search in unstable nuclei. As the first step in the search for the alpha condensed state, the authors searched for the alpha condensed state at ²⁰Ne. They obtained a spectral diagram that is considered to be a strong candidate for the alpha condensed state. They have developed an active target that can detect low energy (0.4 MeV) recoiled alpha particles and measure alpha inelastic scattering, and are analyzing the measured data. This makes it possible to determine the monopole excitation intensity distribution from the excitation energy spectra and search for the cluster state at ¹⁰C. As an example of nucleosynthesis influenced by cluster correlation in the nuclei, this paper explained the triple alpha reaction in which ⁴He captures two alpha particles to synthesize ¹²C. This alpha cluster correlation is closely related to nucleosynthesis in the universe. In order to identify the gamma decay event, the authors newly developed a low background solid hydrogen target and a charged particle detector that can simultaneously measure the protons emitted from inelastic proton scattering and ¹²C, and were able to determine the gamma decay width and gamma decay probability of 3-₁ state. (A.O.)