Vanishing of the N = 20 Magic Number Studied by the Monte Carlo Shell Model

摘要

The structure of unstable nuclei around N = 20 is studied theoretically by the Monte Carlo shell model (MCSM). We focus mainly upon the vanishing of the N = 20 magic structure in this region. The binding energies, the energy levels, and the B(E2) values are well reproduced by the MCSM, and some of them are predicted successfully. We discuss the mechanism of the vanishing in terms of the effective single-particle energy, pointing out that the strong T = 0 monopole interaction between the 0d_(5/2) and 0d_(3/2) plays an important role on the vanishing of the N = 20 magic number and the appearance of the new N = 16 one. The location of F drip line is discussed along the lines.