ELECTRON NUCLEAR DOUBLE RESONANCE RESONATOR FOR DNP & ENDOR AT 5 TESLA

电子核双共振实验需要强 微波和射频场在样品位置。 一 典型的DNP设置针对NMR通道进行了优化， 简单地喷洒到NMR线圈中的样品上，从而浪费了 大量的入射微波功率。 以标准 高场ENDOR探头，优化了微波信号通道 使用具有外部安装NMR的高Q微波谐振器 线圈，导致射频效率的实质性损失 这是由于金属谐振器的屏蔽。 我们已经开发出一种新 双谐振谐振器，允许高效率的微波和 和射频辐射。 该设计基于圆柱形 在TEO模式下工作的腔。 与传统的 设计，微波腔体的实心体已被替换为 缠绕的扁平线，其形成NMR线圈，同时保持高的 微波辐射的品质因数（Q10 aded- 1000）。 在DNP 使用4-氨基克里思作为极化剂的实验，我们已经表明 使用这种谐振器，结合低微波功率， 设置（17 mW）导致F-=300-400的H-信号增强。 以前，这个数量级（F-=185）只能通过以下方法获得： 使用我们的高功率微波回旋管（1-5瓦）。 对于ENDOR 实验表明，射频脉冲长度减少了一个因子~！ 4 与标准ENDOR设置相比， 对低Y核ENDOR的灵敏度更高。 表现 用铁簇蛋白上的13 C-ENDOR证明， 由于电子弛豫非常短， 铁（S=1/2）簇的2 H-ENDOR， 全氘代BDPA稳定自由基。

Electron Nuclear Double Resonance experiments require both strong microwave and radio frequency fields at the sample position. A typical DNP setup is optimized for the NMR channel and microwaves are simply sprayed onto the sample in the NMR coil, thereby wasting a significant amount of the incident microwave power. In a standard high field ENDOR probe, the microwave signal channel is optimized using a high Q microwave resonator with an externally mounted NMR coil, resulting in a substantial loss of radio frequency efficiency due to the shielding of the metal resonator. We have developed a new double resonance resonator allowing high efficiency for both microwave and radio frequency irradiation. The design is based on a cylindrical cavity operating in the TEO,, mode. In contrast to the conventional design, the solid body of the microwave cavity has been replaced by a wound flat wire, which forms the NMR coil while maintaining a high quality factor for microwave irradiation (Q10aded - 1000). In DNP experiments using 4-amino TEMPO as polarizing agent, we have shown that the use of this resonator, combined with a low microwave power setup (17 mW) leads to a 'H-signal enhancement of F-=300-400. Previously, this order of magnitude (F-=185) could be obtained only by using our high power microwave gyrotron (1-5 Watt). For ENDOR experiments the RF pulse lengths are reduced by a factor ~! 4 compared to the standard ENDOR setup, which allows for substantial higher sensitivity on low Y-nuclei ENDOR. The performance was demonstrated with 13 C-ENDOR on an iron-cluster protein, where short irradiation time is required due to very short electronic relaxation times of the iron (S=1/2) cluster, as well as with 2 H-ENDOR on a perdeuterated BDPA stable radical.