โ Scribed by V. Weis; M. Bennati; M. Rosay; J.A. Bryant; R.G. Griffin
No coin nor oath required. For personal study only.
We describe a new triply tuned (e ุ , 1 H, and 13 C) resonance structure operating at an electron Larmor frequency of 139.5 GHz for dynamic nuclear polarization (DNP) and electron nuclear double-resonance (ENDOR) experiments. In contrast to conventional double-resonance structures, the body of the microwave cavity simultaneously acts as a NMR coil, allowing for increased efficiency of radiofrequency irradiation while maintaining a high quality factor for microwave irradiation. The resonator design is ideal for low-โฅ-nuclei ENDOR, where sensitivity is limited by the fact that electron spin relaxation times are on the order of the RF pulse lengths. The performance is demonstrated with 2 H ENDOR on a standard perdeuterated bis-diphenylene-phenyl-allyl stable radical. In DNP experiments, we show that the use of this resonator, combined with a low microwave power setup (17 mW), leads to significantly higher 1 H signal enhancement (โ ฯณ 400 ุ 50) than previously achieved at 5-T fields. The results emphasize the importance of optimizing the microwave B 1 field by improving either the quality factor of the microwave resonator or the microwave power level.
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