Cross Polarization of Unstable Nuclei and Its Application

提出了一种新的极化不稳定原子核的方法，该方法适用于高能重离子反应中产生的弹丸破片。该方法包括以下四个阶段：1。激光光泵浦在Rb原子中产生偏振的研究，2。2 . Rb-Xe原子碰撞过程中Rb极化向^<129>Xe核的超精细相互作用转移；通过冷冻Xe和4的极化气体产生极化的Xe固体。弹丸碎片在极化的Xe固体中植入，随后由宿主Xe自旋使植入物发生交叉极化。到目前为止，本研究得到的结果是：1。在直径22 mm，长40 mm的耐热玻璃电池中成功地极化了Agaseous Xe。在p=10torr的Xe气体压力下，极化率P_<Xe>=60%。P_<Xe>随p的增大而减小，P_<Xe>随p的增大而减小，P_<Xe>随p的变化规律可以用基于t的理论很好地解释，并且考虑了Rb-Xe和Xe-Xe碰撞以及Xe自旋壁相互作用是自旋转移和弛豫的来源。为了获得较高的P_<Xe>值，我们努力消除壁面松弛。结果表明，在细胞内表面涂覆二氯二甲基硅烷可获得长达11 min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，可以被极化到P_<Xe>=7.5-11% 3。由此获得的Xe极化气体从泵站输送到高场区，在那里冷却，并在90mt的外加磁场下冻结成固体。从固体中观察到的核磁共振信号表明，大约35%的初始极化通过输送和冻结保留了下来。需要进一步研究以减少这些过程中极化的损失。对植入弹丸破片的核磁共振测量技术进行了研究。用E/A=70-100 MeV/u的重离子束产生了几种富含轻中子的同位素，并进行了β -核磁共振测量。在研制过程中，得到了能被裂解反应本身极化的原子核的磁矩和电四极矩的结果。在此基础上，研究了^<11>Be的交叉极化实验及其在磁矩测量中的应用。少

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