Few Nucleons Configuration Around Heavy Core Nuclei

We formulate the computational method of the overlap integral of the shell-model and cluster-model configurations. The framework is applied to the systems of the core plus two neutrons (n), and the magnitude of the overlap of the shell model configuration $$(\hbox {core} + n + n)$$ and the di-neutron cluster one $$(\hbox {core} +2n)$$ are explored. The overlap integrals are systematically calculated in the systems with the jj-closed cores, and the enhancement due to the occupation of the s or p orbit occurs in the systematic calculation. The effect of the configuration interaction on the shell-cluster overlap integrals is also discussed.