Continuum effect in resonance spectra of neutron-rich oxygen isotopes**Supported by the National Key R&D Program of China (2018YFA0404401), the National Natural Science Foundation of China (11320101004, 11575007), the China Postdoctoral Science Foundation (2018M630018), the CUSTIPEN (China-U.S. Theory Institute for Physics with Exotic Nuclei) funded by the U.S. Department of Energy, Office of Science (DESC0009971), and High-performance Computing Platform of Peking

Abstract

Starting from the CD-Bonn potential, we have performed Gamow shell-model calculations for neutron-rich oxygen isotopes, investigating excitation spectra and their resonant properties. The Gamow shell model is based on the Berggren ensemble, which is capable of treating the continuum effect reasonably in weakly bound or unbound nuclei. To calculate heavier-mass oxygen isotopes, we choose 16O as a frozen core in the Gamow shell-model calculations. The first 2+ excitation energies of the even-even O isotopes are calculated, and compared with those obtained by the conventional shell model using the empirical USDB interaction. The continuum effect is proved to play an important role in the shell evolution near the drip line. We also discuss the effect of the Berggren contour choice. We improve the approximation in the contour choice to give more precise calculations of resonance widths.