Sienkiewicz A, Jaworski M, Smith B G, Fajer P G, Scholes C P
Institute of Physics, Polish Academy of Sciences, Al. Lotnikow 32/46, Warsaw, 02-668, Poland.
J Magn Reson. 2000 Mar;143(1):144-52. doi: 10.1006/jmre.1999.1986.
We present a novel dielectric resonator (DR)-based resonant structure that accommodates aqueous sample capillaries in orientations that are either parallel (i.e., side-access) or perpendicular to the direction of an external (Zeeman) magnetic field, B(0). The resonant structure consists of two commercially available X-band DRs that are separated by a Rexolite spacer and resonate in the fundamental TE(01delta) mode. The separator between the DRs is used to tune the resonator to the desired frequency and, by appropriately drilled sample holes, to provide access for longitudinal samples, notably capillaries containing oriented, spin-labeled muscle fibers. In contrast to the topologically similar cylindrical TE(011) cavity, the DR-based structure has distinct microwave properties that favor its use for parallel orientation of lossy aqueous samples. For perpendicular orientation of a dilute (6.25 microM) aqueous solution of IASL spin label, the S/N ratio was at least one order of magnitude better for the side-access DR-based structure than for a standard TE(102) cavity. EPR spectra acquired for maleimide spin-labeled myosin filaments also revealed ca. 10 times better S/N ratio than those obtained with a standard TE(102) cavity. For the side-access DR with sample capillaries oriented either parallel or perpendicular to the external magnetic field, the Q- and filling factors are in good agreement with the theoretical estimates derived from the distribution of magnetic (H(1)) and electric (E(1)) components.
我们展示了一种基于新型介质谐振器（DR）的谐振结构，该结构可容纳与外部（塞曼）磁场B(0)方向平行（即侧面接入）或垂直的含水样本毛细管。该谐振结构由两个市售的X波段DR组成，它们由Rexolite垫片隔开，并以基本TE(01δ)模式谐振。DR之间的隔板用于将谐振器调谐到所需频率，并通过适当钻孔的样品孔为纵向样品（特别是包含取向的、自旋标记的肌纤维的毛细管）提供接入通道。与拓扑结构相似的圆柱形TE(011)腔不同，基于DR的结构具有独特的微波特性，有利于其用于有损含水样品的平行取向。对于IASL自旋标记的稀（6.25 microM）水溶液的垂直取向，基于侧面接入DR的结构的信噪比至少比标准TE(102)腔高一个数量级。对马来酰亚胺自旋标记的肌球蛋白丝获得的EPR光谱也显示，其信噪比约比用标准TE(102)腔获得的光谱高10倍。对于样品毛细管与外部磁场平行或垂直取向的侧面接入DR，品质因数和填充因数与从磁（H(1)）和电（E(1)）分量分布得出的理论估计值吻合良好。
