Magnetic moments of 17N and 17B

H. Ueno, K. Asahi, H. Izumi, K. Nagata, H. Ogawa, A. Yoshimi, H. Sato, M. Adachi, Y. Hori, K. Mochinaga, H. Okuno, N. Aoi, M. Ishihara, A. Yoshida, G. Liu, T. Kubo, N. Fukunishi, T. Shimoda, H. Miyatake, M. SasakiT. Shirakura, N. Takahashi, S. Mitsuoka, W. D. Schmidt-Ott

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The magnetic moments of 17N and 17B were measured by using spin-polarized radioactive nuclear beams which were obtained from the projectile fragmentation reaction. The observed magnetic moment of 17N, |μ(17N)|=(0.352±0.002)μN, where μN is the nuclear magneton, falls outside the Schmidt lines. By virtue of a simplifying feature of nuclear structure inherent in a p1/2 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 Jπ=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 17B was determined as |μ(17B)|=(2.545±0.020)μN. The result is substantially smaller than the πp1/2 single-particle value, and the shell-model calculations indicate that the quenching of μ largely stems from Jπ=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 17N as well.

Original languageEnglish
Pages (from-to)2142-2151
Number of pages10
JournalPhysical Review C - Nuclear Physics
Issue number5
StatePublished - May 1996
Externally publishedYes


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