Probing the N = 14 subshell closure: g factor of the ²⁶Mg(2₁⁺) state

The first-excited state g factor of ²⁶Mg has been measured relative to the g factor of the ²⁴Mg(2₁⁺) state using the high-velocity transient-field technique, giving g=+0.86±0.10 . This new measurement is in strong disagreement with the currently adopted value, but in agreement with the sd -shell model using the USDB interaction. The newly measured g factor, along with E(21+) and B(E2) systematics, signal the closure of the νd5/2 subshell at N=14 . The possibility that precise g -factor measurements may indicate the onset of neutron pf admixtures in first-excited state even–even magnesium isotopes below ³²Mg is discussed and the importance of precise excited-state g -factor measurements on sd shell nuclei with N≠Z to test shell-model wavefunctions is noted