Exploration of the exotic structure of Ca-74 using the relativistic point-coupling model combined with complex momentum representation

In this paper, the significance, methods, and progress of research on exotic nuclei are introduced. The theoretical framework of the RMFPC-CMR-BCS method developed by combining the complex momentum representation (CMR) and the Bardeen-Cooper-Schrieffer (BCS) methods according to the relativistic point-coupling model is given. This paper focuses on the investigations of the exotic structure of Ca-74 using the developed method. Because single-particle states near the continuous spectrum threshold are crucial to the formation of an exotic structure, the wave function and the density distribution of a single-particle state that are essential for the halo phenomenon are studied in detail. As the 2d(3/2) state with low orbital angular momentum is closest to the continuum threshold, the last nucleon is likely to spread to the 2d(3/2) state after the BCS method is used to deal with the pairing correlation, which increases the radius of the nucleus. Details about the 2d(3/2) state can be found, and it shows the relevance of resonance in the formation of exotic structures.