The study of shell closures in light neutron-rich nuclei

The behavior of the nuclear shell structure far away from the valley of stability is discussed in this paper with an emphasis on the N = 20 magic number. Two experimental examples, namely γ-spectroscopy of 27Ne by 1H(28Ne, 27Ne) reaction and single-particle spectroscopy of 23O by 22O(d, p)23O* → 22O+n process in inverse kinematics, are shown providing indirect indication and a direct evidence for the extreme decrease of the N = 20 shell gap and, consequently, the vanishing N = 20 magicity.