ELECTRIC QUADRUPOLE-MOMENTS OF NEUTRON-RICH NUCLEI B-14 AND B-15

Spin-polarized fragments B-14 and B-15 produced in intermediate-energy projectile fragmentation reactions were implanted in a Mg single crys tal, and the electric quadrupole moments Q for B-14 and B-15 were dete rmined by beta-NMR spectroscopy. The results, \Q(B-14)\ = 29.84 +/- 0. 75 mb and \Q(B-15)\ = 38.01 +/- 1.08 mb, are compared with theoretical models. Shell-model calculations with 0 (h) over bar omega model spac e, using effective charges commonly accepted in this mass region, pred ict values about 40 % larger than the experimental Q(B-15). Agreement is obtained when a much smaller effective charge for neutrons is emplo yed. The Q(B-14) sensitively reflects small admixture of the d(3/2) ne utron configuration and, when combined with the previously obtained da ta for the magnetic moment, determines reliably the ground state wave function of B-14.