Double-magicity of proton drip-line nucleus 22Si with ab initio calculation.

New magic numbers have been discovered in the neutron-rich region of the nuclear chart. However, there has been a lack of research on proton-rich nuclei. 22O, the mirror nucleus of 22Si, is a double-magic nucleus bearing a high E (2 1 +). Whether 22Si exhibits double-magic characters is an intriguing topic. To investigate this matter, we utilized ab initio valence space in-medium similarity renormalization group for 22Si/22O, and their nearby nuclei. Our ab initio calculations provide good descriptions for the double magicity of 22O, as well as the shell evolution of N = 14 and Z = 14 through E (2 1 +). The computed E (2 1 +) indicate that the closure of Z = 14 sub-shell in proton-rich nuclei is weaker than the N = 14 sub-shell closure in their mirror nuclei. Particularly, the calculated E (2 1 +) of 22Si is 800 keV lower than the one of 22O. To further explore the magicity of 22Si, the mirror energy difference (MED) of 26Si/26Mg, 24Si/24Ne, as well as 22Si/22O are calculated. The results demonstrate that the calculated MEDs agree well with available experimental data, and the E (2 1 +) values of 22,24,26Si are all lower than their respective mirror nuclei due to the Thomas-Ehrman shift with large s 1 / 2 occupation. Moreover, our calculation provides that the many-body configurations of the low-lying state of 22Si/22O are nearly identical despite the fact that the states bearing large MED. In conclusion, our ab initio results suggest that 22Si is a double magic nucleus, similar to its mirror nucleus 22O, albeit with a lower E (2 1 +). [ABSTRACT FROM AUTHOR]