Electric quadrupole moments of neutron-rich nuclei 14B and 15B

Spin-polarized fragments 14B and 15B produced in intermediate-energy projectile fragmentation reactions were implanted in a Mg single crystal, and the electric quadrupole moments Q for 14B and 15B were determined by β-NMR spectroscopy. The results, |Q(14B)| = 29.84 ± 0.75 mb and |Q(15B)| = 38.01 ± 1.08 mb, are compared wi models. Shell-model calculations with 0ωω model space, using effective charges commonly accepted in this mass region, predict values about 40 % larger than the experimental Q(15B). Agreement is obtained when a much smaller effective charge for neutrons is employed. The Q(14B) sensitively reflects small admixture of the d32 neutron configuration and, when combined with the previously obtained data for the magnetic moment, determines reliably the ground state wave function of 14B.