1. Magnetic moments ofN17andB17
- Author
-
Akihiro Yoshimi, Naruto Takahashi, N. Aoi, H. Ueno, Koichiro Asahi, Hirohiko Sato, N. Fukunishi, Tadashi Shimoda, Y. Hori, G. Liu, Misao Sasaki, K. Mochinaga, H. Izumi, W. D. Schmidt-Ott, Hiroshi Ogawa, Kyosuke Nagata, Takashi Kubo, M. Adachi, H. Miyatake, Hideki Okuno, S. Mitsuoka, M. Ishihara, A. Yoshida, and T. Shirakura
- Subjects
Physics ,Nuclear and High Energy Physics ,Magnetic moment ,Spin polarization ,Neutron magnetic moment ,010308 nuclear & particles physics ,Nuclear Theory ,Nuclear structure ,01 natural sciences ,Electron magnetic dipole moment ,Spin magnetic moment ,0103 physical sciences ,Nuclear magnetic moment ,Atomic physics ,010306 general physics ,Nuclear magneton - Abstract
The magnetic moments of $^{17}\mathrm{N}$ and $^{17}\mathrm{B}$ were measured by using spin-polarized radioactive nuclear beams which were obtained from the projectile fragmentation reaction. The observed magnetic moment of $^{17}\mathrm{N}$, \ensuremath{\Vert}\ensuremath{\mu}${(}^{17}$N)\ensuremath{\Vert}=(0.352\ifmmode\pm\else\textpm\fi{}0.002)${\mathrm{\ensuremath{\mu}}}_{\mathit{N}}$, where ${\mathrm{\ensuremath{\mu}}}_{\mathit{N}}$ is the nuclear magneton, falls outside the Schmidt lines. By virtue of a simplifying feature of nuclear structure inherent in a ${\mathit{p}}_{1/2}$ valence nucleus, the deviation from the Schmidt value is attributed on firm ground to admixing of the configurations in which two neutrons in the sd shell are coupled to ${\mathit{J}}^{\mathrm{\ensuremath{\pi}}}$=${2}^{+}$. This interpretation is confirmed in standard shell-model calculations. The calculations reproduce fairly well the experimentally inferred amount of ${2}^{+}$ admixture, as well as the experimental magnetic moment itself. The magnetic moment for $^{17}\mathrm{B}$ was determined as \ensuremath{\Vert}\ensuremath{\mu}${(}^{17}$B)\ensuremath{\Vert}=(2.545\ifmmode\pm\else\textpm\fi{}0.020)${\mathrm{\ensuremath{\mu}}}_{\mathit{N}}$. The result is substantially smaller than the \ensuremath{\pi}${\mathit{p}}_{1/2}$ single-particle value, and the shell-model calculations indicate that the quenching of \ensuremath{\mu} largely stems from ${\mathit{J}}^{\mathrm{\ensuremath{\pi}}}$=${2}^{+}$ configurations of the sd neutrons. The observed amount of quenching, however, is larger than the shell-model predictions, suggesting an enhanced contribution of the ${2}^{+}$ neutron configurations. This result is explained if the pairing energy for neutrons in the sd shell of a neutron-rich nucleus is assumed to diminish by about 30%. We also find that the use of the reduced pairing energy improves agreements in the magnetic moment and low-lying energy levels of $^{17}\mathrm{N}$ as well. \textcopyright{} 1996 The American Physical Society.
- Published
- 1996
- Full Text
- View/download PDF