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The nuclear magnetic dipole moment mu and electric quadrupole moment Q of the beta-emitting 16N(Ipi = 2(-), T(1/2) = 7.13 s) nucleus have been determined for the first time by detecting its beta-NMR in a MgO crystal and beta-NQR (nuclear quadrupole resonance) in a TiO (2) crystal to be /mu/ = (1.9859+/-0.0011) mu(N) and /Q/ = (17.9+/-1.7) mb, respectively. Although the prediction of mu given by the Hartree-Fock calculation agrees well with the experiment, an abnormally small effective charge for neutrons is required to account for the experimental Q.

The quadrupole moment of the $^{8}\mathrm{B}$ (${\mathit{I}}^{\mathrm{\ensuremath{\pi}}}$=${2}^{+}$, ${\mathit{T}}_{1/2}$=769 msec) nucleus was measured as \ensuremath{\Vert}Q${(}^{8}$B)\ensuremath{\Vert}=68.3\ifmmode\pm\else\textpm\fi{}2.1 mb by use of modified \ensuremath{\beta}-NMR. This value is twice as large as the prediction of the Cohen-Kurath shell model. It is found by subtracting the contribution of deeply bound neutrons that the protons in $^{8}\mathrm{B}$ carry more than 90% of the observed moment. The anomalous value is accounted for fairly well by the proton halo due to the loosely bound valence configuration. This is the first experimental evidence for the existence of a proton halo covering a neutron core.

The half-life of the {ital T}=3/2 nucleus {sup 13}O has been remeasured to be {ital T}{sub 1/2}=(8.55{plus minus}0.05) ms by observing a time spectrum of {beta}-delayed protons. This value is appreciably smaller than previously reported. Branching ratios of the {beta} transitions to the ground and excited states of {sup 13}N have been obtained from the proton energy spectrum and the proton-to-{beta} intensity ratio. Mirror asymmetry in the {ital ft} value deduced for the ground-state transition is found to be consistent with the theoretical estimate which takes account of nuclear asymmetry due to the Coulomb interaction.

Nuclear spin polarization of projectile-like fragments /sup 12/B produced in (/sup 14/N,/sup 12/B) reactions at around the classical grazing angle was measured as a function of reaction Q-italic value at incident energies of 120 and 200 MeV. Large positive /sup 12/B polarization was observed in the region of small kinetic energy loss for heavy target nuclei ranging from /sup 232/Th to /sup nat/Fe, and it was interpreted in terms of direct two-proton transfer. For the target nucleus /sup 27/Al, however, large negative polarization was observed in the region of small kinetic energy loss. It was found that the /sup 45/Sc target nucleus was situated at a crossover point for the sign of the polarization. This fact is explained by assuming coexistence of direct and frictional processes. It is found that the contribution of the frictional process tends to exceed that of the direct process with a decrease of target mass number in the region of small energy loss. In the region of large kinetic energy loss, the dominant mechanism is due to the frictional process. A friction constant of (2.4 +- 0.5) x 10/sup -22/ MeVXfm/sup 2/ is deduced from the present experimental data. This value agrees in order ofmore » magnitude with that obtained from the recent study on the reaction Xe + Bi.« less

Nuclear polarization $P$ of the short-lived $\ensuremath{\beta}$ emitter $^{12}\mathrm{B}$ was produced by the beam-foil interaction and directly determined via asymmetric $\ensuremath{\beta}$ decay. For a single tilted foil, at boron energy ${E}_{\mathrm{B}}=1.0$ MeV, $|P|=1.82(14)%$. This was enhanced to $|P|=4.69(46)%$ by stacking four tilted foils. The dependence of $P$ vs ${E}_{\mathrm{B}}$ was observed for a single tilted foil in the range of ${E}_{\mathrm{B}}=0.6 \mathrm{to} 1.3$ MeV. The sign of $P$ followed that of the tilt angle and was consistent with predictions from electron-density-gradient models.

The coefficients ..cap alpha../sub minus-or-plus/ in the alignment-correlation terms A..cap alpha../sub minus-or-plus/EP/sub 2/(costheta), in /sup 12/B and /sup 12/N decays have been determined; ..cap alpha../sub -/(/sup 12/B) =+(0.006 +- 0.018) %/MeV, and ..cap alpha../sub +/(/sup 12/N) =-(0.273 +- 0.041) %/MeV. The sign of ..cap alpha../sub +/(/sup 12/N) was determined for the first time, by use of an NMR method and measurements on ..beta..-..gamma.. correlation in aligned /sup 12/N. The (..cap alpha../sub -/-..cap alpha../sub +/) result is consistent with strong conservation of vector currents without second-class currents and the (..cap alpha../sub -/+..cap alpha../sub +/) result gives unique information on the time component of the axial-vector current.

Polarization of product $^{12}\mathrm{B}$ in the reaction $^{100}\mathrm{Mo}$($^{14}\mathrm{N}$, $^{12}\mathrm{B}$)$^{102}\mathrm{Ru}$ at 90 MeV was measured as a function of product kinetic energy at the reaction angle of 20\ifmmode^\circ\else\textdegree\fi{}. The polarization was found antiparallel to the vector ${\stackrel{\ensuremath{\rightarrow}}{\mathrm{k}}}_{f}\ifmmode\times\else\texttimes\fi{}{\stackrel{\ensuremath{\rightarrow}}{\mathrm{k}}}_{i}$ for higher-energy $^{12}\mathrm{B}$, while parallel for those with lower energy. The zero crossing occurred at around maximum in the energy spectrum.