DEVELOPMENT OF PULSED ELECTRON NUCLEAR DOUBLE RESONANCE (ENDOR) AT 140 GHZ

我们研制了一台140 GHz的脉冲ENDOR光谱仪， 基于三个新的主要单位的磁铁利用10.4 T 超导扫描线圈和2 H-NMR场锁系统，139.5 GHz微波桥，具有四相功能， 反射模式和EPR/NMR双共振探针。 探针 由适于RF辐射的TEOI I腔和 具有用于变量自动调谐能力的高质量谐振电路 射频辐射 对于脉冲EPR，我们获得90* 脉冲， 在20 K时，绝对灵敏度为3.109自旋/高斯。 用脉冲ENDOR实验验证了光谱仪的性能 标准双-二亚苯基-苯基-烯丙基（BDPA）掺杂到 聚苯乙烯和来自E.大肠杆菌核糖核苷酸 还原酶（RNR）。 RNR酪氨酰自由基的EPR谱显示 在5 T下具有显著的g各向异性，并用于证明 方向选择性Davies-ENDOR。

We developed a spectrometer for pulsed ENDOR at 140 GHz, which is based on three new main units a magnet utilizing a 1 0.4 T superconducting sweep coil and a 2 H-NMR field lock system, a 139.5 GHz microwave bridge with four phase capabilities operating in reflection mode, and a probe for EPR/NMR double resonance. The probe consists of a TEOI I cavity adapted for RF irradiation and a high-quality resonance circuit with autotuning capability for variable radio frequency irradiation. For pulsed EPR we obtain 90* pulses of 60 - 70 ns and an absolute sensitivity of 3.109 spins/Gauss at 20 K. The performance of the spectrometer was demonstrated with pulsed ENDOR spectra of a standard bis-diphenylene-phenyl-allyl (BDPA) doped into polystyrene and of the tyrosyl radical from E. coli Ribonucleotide Reductase (RNR). The EPR spectrum of the RNR tyrosyl radical displays substantial g-anisotropy at 5 T and was used to demonstrate orientation selective Davies-ENDOR.