Quadrupole moments of neutron-deficient 20,21Na

Abstract The electric-quadrupole coupling constant of the ground states of the proton drip line nucleus 20 Na ( I π = 2 + , T 1 / 2 = 447.9 ms ) and the neutron-deficient nucleus 21 Na ( I π = 3 / 2 + , T 1 / 2 = 22.49 s ) in a hexagonal ZnO single crystal were precisely measured to be | e q Q / h | = 690 ± 12 kHz and 939 ± 14 kHz , respectively, using the multi-frequency β -ray detecting nuclear magnetic resonance technique under presence of an electric-quadrupole interaction. An electric-quadrupole coupling constant of 27 Na in the ZnO crystal was also measured to be | e q Q / h | = 48.4 ± 3.8 kHz . The electric-quadrupole moments were extracted as | Q ( Na 20 ) | = 10.3 ± 0.8 e fm 2 and | Q ( Na 21 ) | = 14.0 ± 1.1 e fm 2 , using the electric-coupling constant of 27 Na and the known quadrupole moment of this nucleus as references. The present results are well explained by shell-model calculations in the full sd -shell model space.