The electric-quadrupole coupling constant of the ground states of the proton
drip line nucleus 20Na(IĻ = 2+, T1/2ā = 447.9 ms) and the
neutron-deficient nucleus 21Na(IĻ = 3/2+, T1/2ā = 22.49 s)
in a hexagonal ZnO single crystal were precisely measured to be ā£eqQ/hā£=690Ā±12 kHz and 939 Ā± 14 kHz, respectively, using the multi-frequency
Ī²-ray detecting nuclear magnetic resonance technique under presence of an
electric-quadrupole interaction. A electric-quadrupole coupling constant of
27Na in the ZnO crystal was also measured to be ā£eqQ/hā£=48.4Ā±3.8
kHz. The electric-quadrupole moments were extracted as ā£Q(20Na)ā£ = 10.3
Ā± 0.8 e fm2 and ā£Q(21Na)ā£ = 14.0 Ā± 1.1 e fm2, using
the electric-coupling constant of 27Na 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.Comment: Accepted for publication in Physics Letters