Study of Bohr-Weisskopf effect using low-temperature nuclear orientation

利用低温核取向研究玻尔-韦斯科普夫效应

• 批准号: 13640270
• 负责人: OHYA Susumu
• 金额: $ 2.18万
• 依托单位: NIIGATA UNIVERSITY
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (C)
• 财政年份: 2001
• 资助国家: 日本
• 起止时间: 2001 至 2002
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-13640270/
• 关键词: Nuclear orientation; Bohr-Weisskopf effect; Hyperfine anomaly; Nuclear Magnetic resonance on oriented nuclei; 低温各偏極; Bohr-Weisskopt効果

The hyperfine anomaly arises from the hyperfine interaction of the finite nuclear volume of nuclear magnetization and the hyperfine field due to Fermi-contact. The difference between the point nuclear magnetic structure and the finite magnetic structure is referred as Bohr-Weisskopf effect [2], which depends on the nuclear structure. If the spin and orbital contributions to the magnetic moment have opposite sign, the large hyperfine anomaly is expected. The study of Bohr-Weisskopf effect by this project was carried on for two years from 2001.Nuclear magnetic resonance on oriented nuclei (NMR-ON) experiments on Sc isotopes (A=44, 44m, 46, 47, 48) have been performed at about 10mK. The samples were prepared by recoil implantation into Fe foils using α- beams at CYRIC cyclotron, Tohoku University. The activated part of the foil was cooled down to about 10mK by a ^3He/^4He dilution refrigerator. All NMR-ON resonances for Sc isotopes (A=44, 44m, 46, 47, 48) were observed. The values of magnetic moments except ^<48>Sc are already known by the atomic beam method. From these results, the values of the hyperfine field of ^<47>ScFe and the magnetic moment of ^<48>Sc were determined as -13, 17(5) T and 3.79(1)μ_<N_3> respectively. Comparing with ^<44m>Sc the effects of Bohr-Weisskopf were determined as; ^<44>ScΔ^<44m>Sc = -1.2(12)%, ^<46>ScΔ^<44m>Sc = 1.3(7)%, ^<47>ScΔ^<44m>Sc = -1.3(7)%. We also made the sample of ^<91g.m>YFe using the mass separator at Kyoto Univ.. The NMR-ON resonances for both isotopes were observed. From the values of the resonance frequencies versus the external magnetic fields, the effects of Bohr-Weisskopf was determined as ^<91>YΔ^<91m>Y = -1(3)%. The ^<91>Y case is that the spin and orbital contributions to the magnetic moment have opposite sign. The theoretical estimation from Fujita and Arima yields that the effect is -4-5%. Detailed analysis are now in progress.

超精细异常是由核磁化有限核体积的超精细相互作用和由于费米接触引起的高精细场。点核磁性结构和有限磁结构之间的差异称为bohr-weisskopf效应[2]，它取决于核结构。如果自旋和轨道对磁矩的贡献相反，则预计大型高精细异常。从2001年开始对该项目进行了两年的Bohr-Weisskopf效应。对SC同位素的定向核（NMR-ON）实验（A = 44、44m，46、46、47、48）的核磁共振已在约10MK时进行。通过在Tohoku University的Cyric Cyclotron上使用α-梁植入fe箔来制备样品。通过A ^3he/ ^4he稀释冰箱将箔的活化部分冷却至约10MK。观察到了SC同位素的所有NMR-ON共振（A = 44、44M，46、47、48）。除 ^<48> sc以外的磁矩的值已经通过原子束法知道。从这些结果中，分别确定 ^<47> scfe和 ^<48> sc的磁矩的高精细场的值分别确定为-13、17（5）T和3.79（1）μ__<n_3>。与 ^<44m> SC相比，Bohr-Weisskopf的效果被确定为； ^<44>scδ^<44m> sc = -1.2（12）％，^<46>scδ^<44m> sc = 1.3（7）％，^<47>scδ^<44m> sc = -1.3（7）％。我们还使用京都大学的质量分离器制作了 ^<91g.m> yfe的样本。观察到了两种同位素的NMR-ON共振。从共振频率与外部磁场的值中，Bohr -Weisskopf的效果被确定为 ^<91>yδ ^<91m> y = -1（3）％。 ^<91> y的情况是，旋转和轨道对磁矩的贡献具有相反的符号。富士和阿里玛的理论估计得出的效果为-4-5％。现在正在进行详细的分析。