Cross Polarization of Unstable Nuclei and Its Application

不稳定原子核的交叉极化及其应用

• 批准号: 06640379
• 负责人: ASAHI Koichiro
• 金额: $ 1.28万
• 依托单位: Tokyo Institute of Technology
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for General Scientific Research (C)
• 财政年份: 1994
• 资助国家: 日本
• 起止时间: 1994 至 1995
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-06640379/
• 关键词: Nuclear Spin Polarization; Optical Pumping; Nuclear Magnetic Moment; Nuclear Magnetic Resonance; Radioactive Nuclear Beam; Projectile Fragmentation Reaction

New method of polarizing unstable nuclei has been developed, which is applicable to the projectile fragments produced in the high-energy heavy-ion reaction. The method consists of the following four stages : 1.Production of polarization in Rb atoms by means of the laser optical pumping, 2.transfer of the Rb polarization to ^<129>Xe nuclei through the hyperfine interactions inthe course of Rb-Xe atomic collisions, 3.production of a polarized Xe solid by freezing the polarized gas of Xe, and 4.implantation of projectile fragments in the polarized Xe solid and subsequent cross polarization of the implants by the host Xe spins. Results obtained untilnow in the present investigation are :1.Agaseous Xe was successfully polarized in a pyrex glass cell, 22 mm in diameter, 40 mm in length. Polarization P_<Xe>=60% was attained at the Xe gas pressure of p=10torr. P_<Xe> was found to decrease with increasing p. The whole behavior of P_<Xe> as a function of p was well explained by theory based on t … More he consideration of Rb-Xe and Xe-Xe collisios and Xe spin-wall interaction as sources of spin transfer and relaxation.2.Efforts were made to eliminate the wall relaxation in order to achieve a high value of P_<Xe>. As a result, a wall relaxation time T_w as long as 11 min was attained by coating the inner surface of the cell with dichlorodimethylsilane. With such a value of T_w,10^<21> atoms of Xe, amounting to a solid Xe of 5*5*1mm^3 volume, can be polarized to P_<Xe>=7.5-11%.3.Apolarized gas of Xe thus obtained was transported from the pumping station to a high-field region, cooled there, and frozen into a solid under an applied field of 90 mT.Observed NMR signals from the solid indicated that about 35% of the initial polarization was retained through the transportation and freezing. Further investigation is needed to reduce loss of polarization in these procedures.4.Development was made of the beta-NMR measurement technique on implanted projectile fragments. Heavy-ion beams at E/A=70-100 MeV/u were used to produce several light neutron-rich isotopes, and the beta-NMR measurements were made. In the course of development, results were obtained for magnetic moments and electric quadrupole moment of those nuclei which could be polarized by the fragmentation reaction itself.Based on the outcome presented above, the cross polarization experiment of ^<11>Be and its application to the magnetic moment measurement are now under consideration. Less

开发了一种极化不稳定核的新方法，适用于高能重离子反应中产生的弹丸碎片。该方法由以下四个阶段组成：1.通过激光光泵浦在Rb原子中产生偏振，2.通过Rb-Xe原子碰撞过程中的超精细相互作用将Rb偏振转移到^<129>Xe核，3.通过冻结Xe的偏振气体产生偏振Xe固体，以及4.将射弹碎片植入偏振Xe中 固体以及随后由主体 Xe 自旋引起的注入物的交叉极化。到目前为止，本研究获得的结果是： 1.气态氙在直径为22毫米、长度为40毫米的派热克斯玻璃池中成功极化。在p＝10torr的Xe气压下获得偏振P_<Xe>＝60％。发现 P_<Xe> 随着 p 的增加而减少。 P_<Xe> 作为 p 的函数的整个行为可以通过基于 Rb-Xe 和 Xe-Xe 碰撞以及 Xe 自旋壁相互作用作为自旋转移和弛豫源的理论得到很好的解释。2.努力消除壁弛豫以获得高值的 P_<Xe>。结果，通过用二氯二甲基硅烷涂覆电池的内表面，获得了长达11分钟的壁弛豫时间T_w。在这样的T_w值下，10^<21>个Xe原子，相当于5*5*1mm^3体积的固体Xe，可以极化到P_<Xe>=7.5-11%。 3.将由此获得的非极化Xe气体从泵站输送到高场区域，在那里冷却，并在90mT的施加场下冻结成固体。从固体观察到的NMR信号表明： 通过运输和冷冻保留了约35%的初始极化。需要进一步研究以减少这些程序中的极化损失。4.开发了植入弹丸碎片的β-NMR测量技术。使用 E/A=70-100 MeV/u 的重离子束产生几种轻中子富同位素，并进行 β-NMR 测量。在开发过程中，获得了那些可以通过碎裂反应本身极化的原子核的磁矩和电四极矩的结果。基于上述结果，目前正在考虑^<11>Be的交叉极化实验及其在磁矩测量中的应用。较少的

项目成果

H.Sato et al.: "Development of Polarized ^<129>Xe Stopper as a Polarizer for Unstable Nuclei" 「短寿命核ビームの科学'94」研究会報告集. 55-60 (1995)

H. Sato 等人：“发展极化^<129>Xe Stopper 作为不稳定核的偏振器”“短命核束科学94”研究小组的报告55-60 (1995)。

H.Sato et al.: "Polarized Xe Solid as a Means to Produce Spin Polarization in Stopped Unstable Nuclei" RIKEN Accelerator Prog.Rep.29 (to be published). (1996)

H.Sato 等人：“Polarized Xe Solid as a Means to Produce Spin Polarization in Stopped Unstable Nuclei”RIKEN Accelerator Prog.Rep.29（待出版）。

H.Sato et al.: "Polarized Xe Solid as a Means to Produce Spin Polarization in Stopped Unstable Nuclei" Riken Accelerator Progress Report. 29. (1996)

H.Sato 等人：“极化 Xe 固体作为在停止的不稳定核中产生自旋极化的手段”Riken 加速器进展报告。

H.Izumi et al.: "Electric Quadrupole Moments of Neutron-rich Nuclei ^<14>B and ^<15>B" Phy.Lett.B366. (1996)

H.Izumi 等人：“富中子核^ 14 B 和^ 15 B 的电四极矩”Phy.Lett.B366。

K.Asahi: "Spin-polarized Radiactive Nuclear Beams and Their Applications" Butsuri. 50. 791-798 (1995)

K.Asahi：“自旋极化放射性核束及其应用”Butsuri。