Long-lived Nuclear Hyperpolarization of Methyl Groups

核磁共振（NMR）是一种技术，它利用许多原子的原子核作为微小的无线电发射器，以精确定义的频率发射无线电信号，可以通过仔细调谐的检测器检测到。在核磁共振实验中，首先将样品置于强磁场中一段时间，使原子核磁化。然后将一系列射频脉冲施加到样品上，样品随后发射无线电波，无线电波在无线电接收器中被检测到。发射波的模式提供了样品的化学成分和空间分布的信息。在一般情况下，由原子核发射的NMR和MRI信号相对较弱，因为原子核的磁矩指向随机方向。2003年，一种革命性的方法被开发出来，使原子核暂时相互排列，将核磁共振信号的强度提高了一万倍甚至更多。这种方法被称为溶解-DNP（DNP代表“动态核极化”），英国牛津仪器公司制造并销售了一种实现这种方法的仪器。然而，该技术的缺点是极大增强的偏振（称为超偏振）很快消失。2004年，我们的研究小组发现，对于某些物质，通过使用非磁性的特殊量子态（称为长寿命态），衰变时间可以延长10倍或更多。去年，有证据表明，称为甲基（CH 3）的化学基团支持长寿命态。这些小的对称基团在化学和生物学中非常常见。甲基具有小推进器的形状，并且通常相对于分子的其余部分非常快速地旋转。我们的研究小组表明，这种螺旋桨运动会产生某种长寿命的状态。我们用我们的理论解释了一些以前没有解释过的结果，并进行了第一系列实验来验证理论。在这个项目中，我们将联合收割机这些发展，产生甲基长寿命的状态，是强烈的超极化，并引起大大增强的NMR信号。我们提出了验证和利用含有甲基的分子中的这些状态的方法，这些甲基在天然物质中非常常见。该项目涉及量子力学，工程，实验光谱学和化学合成的跨学科组合，所有这些都是该项目成功的关键。我们将开发和展示一系列新的磁共振方法，这些方法在医学，化学工程和材料科学中具有广泛的应用。

Nuclear Magnetic Resonance (NMR) is a technique which uses the fact that the nuclei of many atoms act as tiny radiotransmitters, emitting radio signals at precisely-defined frequencies, which can be detected by a carefully-tuned detector. In an NMR experiment, the nuclei are first magnetised by placing a sample in a strong magnetic field for some time. A sequence of radiofrequency pulses is then applied to the sample, which subsequently emits radiowaves which are detected in the radio receiver. The pattern of emitted waves provides information on the chemical composition and spatial distribution of the sample.In ordinary circumstances, the NMR and MRI signals emitted by the nuclei are relatively weak, since the magnetic moments of the nuclei point in random directions. In 2003, a revolutionary method was developed for causing the nuclei to temporarily line up with each other, increasing the strength of NMR signals by a factor of ten thousand or even more. This method is called dissolution-DNP (where DNP stands for "dynamic nuclear polarization") and an instrument to implement this is built and marketed by the British company Oxford Instruments. However a drawback of the technique is that the greatly enhanced polarization (called hyperpolarization) dies out quickly. Our group showed in 2004 that for some substances the decay time could be extended by a factor of 10 or more by using special quantum states which are non-magnetic, called long-lived states.Last year evidence was presented that chemical groups called methyl groups (CH3) support long-lived states. These small symmetric groups are very common in chemistry and biology. A methyl group has the shape of a small propellor and usually rotates very rapidly with respect to the rest of the molecule. Our group showed that this propellor motion gives rise to a certain class of long-lived states. We used our theory to explain some prior results that had not been explained before, and performed a first series of experiments to validate the theory. In this project we will combine these developments to generate methyl long-lived states that are strongly hyperpolarized and give rise to greatly enhanced NMR signals. We propose methods for validating and exploiting these states in molecules containing methyl groups, which are very common in natural substances. The project involves an interdisciplinary combination of quantum mechanics, engineering, experimental spectroscopy, and chemical synthesis, all of which are essential for the success of the project. We will develop and demonstrate a range of new magnetic resonance methods with a wide range of applications in medicine, chemical engineering and materials science.