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The magnetic moments of 17 N and 17 B were measured by using spin-polarized radioactive nuclear beams which were obtained from the projectile fragmentation reaction. The observed magnetic moment of 17 N, ͉͑ 17 N͉͒ϭ͑0.352Ϯ0.002͒ N , where N is the nuclear magneton, falls outside the Schmidt lines. By virtue of a simplifying feature of nuclear structure inherent in a 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 J ϭ2 ϩ. This interpretation is confirmed in standard shell-model calculations. The calculations reproduce fairly well the experimentally inferred amount of 2 ϩ admixture, as well as the experimental magnetic moment itself. The magnetic moment for 17 B was determined as ͉͑ 17 B͉͒ϭ͑2.545Ϯ0.020͒ N. The result is substantially smaller than the p 1/2 single-particle value, and the shell-model calculations indicate that the quenching of largely stems from J ϭ2 ϩ 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 ϩ 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 N as well. ͓S0556-2813͑96͒05005-4͔

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