Measurement of electric quadrupole moments of neutron-rich nuclei14B and15B

The experimental study of nuclear moments of several neutron-rich nuclei, using the phenomenon of ejectile spin polarization in the projectile fragmentation reaction, is reported. The spin-polarized fragments 14B and 15B were produced in the fragmentation of 18O projectiles on a Nb target at 64.7 MeV/u. They were implanted into a Mg single crystal, and the quadrupole moments Q were determined by the ��-NMR method. The results, ��18O = 29.84 �� 0.75 mb and (15B)| = 38.01 �� 1.08 mb, are compared with theoretical models. Shell model calculations in a Ofiut 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 method was also applied to the measurement of the magnetic moments of 17N and 17B. The result reveals an important contribution of configurations with excess neutrons coupled to form J�� = 2+. ? J.C. Baltzer AG, Science Publishers.