Configuration mixing effects in neutron-rich carbon isotopes

Shell model calculations are done to study the structure of neutron-rich carbon isotopes. For both even-A and odd-A neutron-rich carbon isotopes, the energy levels are strongly affected by the configuration mixing of valence neutrons. The calculated energy levels in the nucleus ¹⁷C are significantly improved compared with experimental values when the model space of the three valence neutrons is enlarged from pure v(0d_5/2)³ configuration to full sd space. We also investigate the configuration mixing effect on the B(E2) values in even-even nuclei ^16-20C.