National Biomedical EPR Center, Department of Biophysics, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, WI 53226, USA; Department of Physics and Chemistry, Milwaukee School of Engineering, 1025 North Broadway, Milwaukee, WI 53202, USA.
National Biomedical EPR Center, Department of Biophysics, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, WI 53226, USA.
J Magn Reson. 2019 Oct;307:106585. doi: 10.1016/j.jmr.2019.106585. Epub 2019 Aug 28.
The performance of a metallic microwave resonator that contains a dielectric depends on the separation between metallic and dielectric surfaces, which affects radio frequency currents, evanescent waves, and polarization charges. The problem has previously been discussed for an X-band TE cylindrical cavity resonator that contains an axial dielectric tube (Hyde and Mett, 2017). Here, a short rutile dielectric tube inserted into a loop-gap resonator (LGR) at X-band, which is called a dielectric LGR (dLGR), is considered. The theory is developed and experimental results are presented. It was found that a central sample loop surrounded by four "flux-return" loops (i.e., 5-loop-4-gap) is preferable to a 3-loop-2-gap configuration. For sufficiently small samples (less than 1 µL), a rutile dLGR is preferred relative to an LGR both at constant Λ (B/P) and at constant incident power. Introduction of LGR technology to X-band EPR was a significant advance for site-directed spin labeling because of small sample size and high Λ. The rutile dLGR introduced in this work offers further extension to samples that can be as small as 50 nL when using typical EPR acquisition times.
一个包含电介质的金属微波谐振器的性能取决于金属和电介质表面之间的距离，这会影响射频电流、消逝波和极化电荷。此前，Hyde 和 Mett（2017）已经讨论过包含轴向电介质管的 X 波段 TE 圆柱腔谐振器的问题。这里考虑了在 X 波段将一个短的金红石电介质管插入环形间隙谐振器（LGR）中，称为介电 LGR（dLGR）。本文提出了相关理论并给出了实验结果。研究发现，与 3 环 2 间隙结构相比，中心样品环被四个“磁通返回”环（即 5 环 4 间隙）包围的结构更为可取。对于足够小的样品（小于 1µL），与 LGR 相比，在保持 Λ（B/P）和入射功率不变的情况下，金红石 dLGR 更为可取。将 LGR 技术引入 X 波段 EPR 对于基于位置的自旋标记是一个重大进展，因为它的样品体积小，Λ 高。在这项工作中引入的金红石 dLGR 进一步扩展了可以小至 50 nL 的样品，这在典型的 EPR 采集时间内是可行的。
