Shell-model study of boron, carbon, nitrogen, and oxygen isotopes with a monopole-based universal interaction

We study boron, carbon, nitrogen, and oxygen isotopes with a newly constructed shell-model Hamiltonian developed from a monopole-based universal interaction (VMU). The present Hamiltonian can reproduce well the ground-state energies, energy levels, electric quadrupole properties, and spin properties of these nuclei in full $psd$ model space including (0-3)ω excitations. Especially, it correctly describes the drip lines of carbon and oxygen isotopes and the spins of the ground states of ¹⁰B and ¹⁸N while some former interactions such as WBP and WBT fail. We point out that the inclusion of 2ω excitations is important in reproducing some of these properties. In the present (0+2)ω calculations small but constant $E2$ effective charges appear to work quite well. As the inclusion of the 2ω model space makes a rather minor change, this seems to be related to the smallness of the ⁴He core. Similarly, the spin g factors are very close to free values. The applicability of tensor and spin-orbit forces in free space, which are taken in the present Hamiltonian, is examined in shell-model calculations.