International Research Fellowship Program: Fundamental Studies of Spin-Exchange Optical Pumping for the Production of Large Quantities of Highly Spin-Polarized Noble Gases

国际研究奖学金计划使美国科学家和工程师能够在国外进行9到24个月的研究。 该计划的奖项提供了联合研究的机会，以及使用独特或互补的设施，专业知识和国外的实验条件。该奖项将支持由尼古拉斯·怀汀博士与迈克尔·J·巴洛博士，彼得·莫里斯，和英国诺丁汉大学的托马斯米尔斯曼，以及年南伊利诺伊大学卡本代尔分校的博伊德古德森博士，美国？极端化？(HP)惰性气体可用于增强磁共振（MR）检测灵敏度，用于许多潜在的和已实现的应用。因为在常规MR方法中实现的核自旋极化通常在~10 - 5？10 - 6，数量级更高的自旋极化表现出这样的HP气体可以直接转化为相应的大规模增强MR检测灵敏度？从而能够进行广泛的新颖实验和方法，这在其他情况下是不可能的。产生HP气体的主要方法之一是自旋交换光泵浦（SEOP）。SEOP是一个两步过程，其中角动量从共振的圆偏振激光转移到碱金属蒸气的电子自旋，然后通过碰撞转移到惰性气体的核自旋。使得核自旋极化随时间积累。SEOP背后的基本物理过程是令人惊讶的多方面和相互依赖的，尽管对这些过程的光学，原子和分子物理学进行了数十年的研究，但它们尚未得到充分的探索;事实上，还有很多不知道或不理解的东西？特别是当在与MR应用最相关的关键机制和实验条件下执行SEOP时。拟议的研究的目标是获得更深入的基本了解SEOP过程涉及选定的碱金属和稀有气体，并应用这些见解，以改善SEOP MR应用需要大量的高自旋极化气体。拟议中的研究将涉及使用铷（Rb）和铯（Cs）作为碱金属，氙-129（129Xe）和氪-83（83Kr）作为惰性气体物质的SEOP（有可能扩大到131毫米）;虽然Rb/129 α SEOP在过去已被很好地表征，（尽管不是在本工作提出的条件下），涉及Cs/129氪的研究以及提高四极83氪/131氪同位素的极化和MR应用的努力在很大程度上仍处于起步阶段。在主办机构的基本SEOP过程的拟议研究包括：碱金属电子自旋极化（PRb/PC）分布的依赖性？地图？使用光学电子自旋共振（ESR）光谱学对惰性气体类型和密度、电池温度、总压力、激光通量、光谱偏移等进行研究;对OP电池内的能量传输机制进行研究（作为相同参数的函数）使用拉曼光谱测量氮气的振转温度;以及通过低场3-D MR成像研究OP单元上相应的核自旋极化分布（和气体动力学）。诺丁汉仪器？私家侦探会帮你完成吗将第一次允许在真实的时间内比较所有这些实验观测值。这些实验将不仅提供有关SEOP的新知识，但将通知MR应用程序生成HP气体的条件优化？包括提议的实验，将探索使用高自旋极化气体探测多孔材料和表面。虽然拟议的研究是基本的性质，结果？在会议发言和出版物中广泛传播？应该对HP气体的新兴和成熟应用产生直接影响;这些应用是多种多样的，从材料研究到肺空间和组织的临床人体MR成像。诺丁汉大学是唯一的定位，作为主机，鉴于其在国家的最先进的实验仪器，专家人员，并在MR创新强大的历史丰富的资源？提供重要的培训和经验，以及建立长期的国际合作，这将在PI的整个专业研究生涯中产生积极的影响。

0966393WhitingThe International Research Fellowship Program enables U.S. scientists and engineers to conduct nine to twenty-four months of research abroad. The program's awards provide opportunities for joint research, and the use of unique or complementary facilities, expertise and experimental conditions abroad.This award will support a twenty-four-month research fellowship by Dr. Nicholas Whiting to work with Drs. Michael J. Barlow, Peter Morris, and Thomas Meersmann at the University of Nottingham in the United Kingdom and with Dr. Boyd Goodson at Southern Illinois University Carbondale in the United States.?Hyperpolarized? (HP) noble gases can be used to enhance the magnetic resonance (MR) detection sensitivity for a host of potential and realized applications. Because the nuclear spin polarization achieved in conventional MR methods is usually on the order of ~10-5?10-6, the orders-of-magnitude higher spin polarization manifested by such HP gases can translate directly into correspondingly massive enhancements in MR detection sensitivity?thus enabling a wide range of novel experiments and approaches that would not be possible otherwise. One of the primary methods for generating HP gases is spin-exchange optical pumping (SEOP). SEOP is a two-step process where angular momentum is transferred from resonant, circularly polarized laser light to the electronic spins of an alkali metal vapor, and then subsequently transferred to the nuclear spins of a noble gas via collisions?allowing the nuclear spin polarization to accumulate over time. The fundamental physical processes underlying SEOP are surprisingly multifaceted and interdependent, and despite decades of research into the optical, atomic, and molecular physics of these processes, they have yet to be sufficiently explored; indeed, there is much that is not known or understood?particularly when SEOP is performed under key regimes and experimental conditions that are most relevant for MR applications. The objectives of the proposed research are to gain a deeper fundamental understanding of SEOP processes involving selected alkali metals and noble gases, and to apply these insights to improve SEOP for MR applications requiring large amounts of highly spin-polarized gases. The proposed research will involve SEOP using both rubidium (Rb) and cesium (Cs) as alkali metals, and xenon-129 (129Xe) and krypton-83 (83Kr) as noble gas species (with the possibility to expand to 131Xe); while Rb/129Xe SEOP has been well characterized in the past (although not under the conditions proposed in this work), studies involving Cs/129Xe as well as efforts to boost the polarization and MR applications of the quadrupolar 83Kr/131Xe isotopes are still largely in their infancy. The proposed studies of fundamental SEOP processes at the Host institution include: the dependence of the alkali metal electronic spin polarization (PRb/PCs) distribution ?map? on noble gas type and density, cell temperature, total pressure, laser flux, spectral offset, etc. using optical electron spin resonance (ESR) spectroscopy; investigations of energy-transport mechanisms within the OP cell (as a function of the same parameters) using Raman spectroscopy to measure the rovibrational temperature of nitrogen gas; and studies of the corresponding nuclear spin polarization distribution (and gas dynamics) across the OP cell via low-field 3-D MR imaging. The Nottingham apparatus?which the PI will help complete?will for the first time allow the comparison of all of these experimental observables in real time. These experiments will not only provide new knowledge concerning SEOP, but will inform the optimization of conditions for generating HP gases for MR applications?including proposed experiments that will explore the use of highly spin-polarized gases for probing porous materials and surfaces. While the proposed research is fundamental in nature, the results?to be widely disseminated in conference presentations and publications?should have a direct impact on both emerging and established applications of HP gases; such applications are manifold and vary from studies of materials to clinical human MR imaging of lung spaces and tissues. The University of Nottingham is uniquely positioned to serve as host, given its vast resources in state-of-the-art experimental instrumentation, expert personnel, and strong history in MR innovation?providing vital training and experiences, as well as establishing long-lasting international collaborations, that will positively impact the PI throughout the duration of his professional research career.