【作者】 周欣；

【导师】 刘买利； 曾锡之；

【作者基本信息】 中国科学院研究生院（武汉物理与数学研究所） ， 无线电物理， 2004， 博士

【摘要】 激光极化（超极化）¹²⁹Xe,由于其核自旋极化度比热平衡条件下的极化度提高10⁴-10⁵倍,被广泛应用到众多的自然科学领域中,特别是核磁共振中。因此,本学位论文选用激光极化¹²⁹Xe的核磁共振（Nuclear Magnetic Resonance, NMR）研究为题,研究涉及激光极化¹²⁹Xe的产生和存储、NMR辐射阻尼动力学、自旋极化诱导核的Overhauser效应（Spin Polarized-Induced Nuclear Overhauser Effect, SPINOE）和NMR谱仪和探头技术四方面的工作,主要包括以下内容:建立了一套在低磁场流动系统下,利用自旋交换光泵（Spin-Exchange Optical Pumping, SEOP）产生激光极化¹²⁹Xe的实验装置。并首次在无氮气的条件下,利用激光光泵Cs原子的D₂线形成高度极化的Cs原子,随后再与惰性气体¹²⁹Xe进行自旋交换,获得了比热平衡条件下,极化度增强大于10000倍、5000倍和6000倍的气态、液态和固态的激光极化¹²⁹Xe的NMR信号。在77 K和2800 Gauss的条件下,激光极化固态¹²⁹Xe的存储时间超过3小时。实验上,首次观测到了低磁场流动系统下,激光极化¹²⁹Xe的液态和气态NMR辐射阻尼信号,并研究了在不同脉冲反转角的激发下,激光极化液态¹²⁹Xe的辐射阻尼动力学行为。理论上,拟合得到激光极化液态¹²⁹Xe的辐射阻尼时间常数,并模拟了在不同脉冲反转角的激发下,当横向弛豫和辐射阻尼相互竞争时,自由感应衰减（Free Induction Decay, FID）信号包络和谱图线形的变化。实验上,首次利用激光极化¹²⁹Xe,通过SPINOE的方法,获得了固态1HCl中增强6倍的质子NMR信号。理论上,推导了在磁偶极—偶极相互作用下,固态的SPINOE极化增强公式,并通过此公式计算出理论增强值为7.1倍,与实验值符合。在实验还获得了,通过SPINOE增强天然丰度¹³C的NMR信号。总结和分析了在上述NMR实验中,Bruker AC-80 NMR谱仪的常见故障,并给出了相应的解决方案。另外,还给出了激光极化¹²⁹Xe的探头电路,并分析说明了调试中应该注意的问题。更多还原

【Abstract】 Laser-polarized （hyperpolarized） ¹²⁹Xe, whose nuclear spin polarization can be increased by four or five orders of magnitude over the equilibrium Boltzmann polarization, has been widely used in many fields of natural sciences, especially in nuclear magnetic resonance （NMR）. Therefore, the‘study of laser-polarized ¹²⁹Xe via NMR’is chosen as the subject of this dissertation, which involves the production and storage of laser-polarized ¹²⁹Xe, radiation damping of laser-polarized ¹²⁹Xe in NMR, spin polarized-induced nuclear Overhauser effect （SPINOE） via laser-polarized ¹²⁹Xe, and the techniques of NMR spectrometer and probe. Significant results are shown as follows:An experimental setup for production of laser-polarized ¹²⁹Xe via spin-exchange optical pumping （SEOP） at low magnetic field in a flow system has been constructed. Based on this setup, in absence of nitrogen gas, production of the laser-polarized ¹²⁹Xe via spin-exchange with optically pumped Cs atoms at the D2 line was firstly reported. The nuclear polarizations of laser-polarized ¹²⁹Xe have been enhanced by factors over 10000, 5000 and 6000 for the gaseous, liquid and solid state, respectively, comparing with those at thermal equilibrium. The storage time of solid laser-polarized ¹²⁹Xe has exceeded three hours at 77 K and 2800 Gauss.The NMR radiation damping effects of the gaseous and liquid laser-polarized ¹²⁹Xe have been firstly observed at low magnetic field in a flow system, and the dynamics of radiation damping has been experimentally studied with different pulse flip angles. The radiation damping time constant of the liquid laser-polarized ¹²⁹Xe was derived on the basis of the theoretical simulation. The envelopes of the ¹²⁹Xe free induction decay （FID） and the spectral lineshape have been theoretically simulated, in the presence of both the transverse relaxation and the radiation damping with different pulse flip angles.For the first time, the solid NMR signal enhancement of 6 for the proton （¹HCl） has been achieved via SPINOE with laser-polarized ¹²⁹Xe. The formula for the SPINOE enhancement in solid state has been theoretically deduced on the basis of the spin-spin dipole-dipole interaction, and the theoretical calculated enhancement of about 7.1 is in agreement with the experimental one. The enhanced ¹³C NMR signal with the更多还原