Magnetic Moments of Short-Lived β-Radioactive Nuclei, 12B and 12N

The magnetic moments of 12 B( T 1/2 =20 ms) and 12 N( T 1/2 =11 ms) have been determined by an NMR method using the recoil polarization and the asymmetric β decay. The nuclear polarization was preserved by using a holding static magnetic field and a recoil stopper of metal foil. Several kinds of metal foils were employed. Relative shifts of the order of 10 -3 between the centers of NMR by different metals and the resonance widths comparable to the dipolar broadening were observed. The results obtained for the magnetic moments are µ( 12 B, 1 + )=+(1.003±0.001) nm and µ( 12 N, 1 + )=+(0.4571±0.0005) nm.