Piasecki W, Froncisz W, Hubbell W L
Department of Biophysics, Institute of Molecular Biology, Jagiellonian University, Al. Mickiewicza 3, Kraków, 31-120, Poland.
J Magn Reson. 1998 Sep;134(1):36-43. doi: 10.1006/jmre.1998.1482.
A new rectangular geometry of the loop-gap resonator for the use with a flat cell has been developed. Maxwell's equations for the resonators with two, four, six, and eight gaps have been solved assuming the existence of only the magnetic z-component. The formulas obtained were numerically solved for the electric and magnetic field distributions over the cross-sections of the resonators. The presence of a nodal plane for the electric field in the center of the resonator allows the use of a flat cell instead of a capillary for EPR measurements. Using the field distributions obtained, the quality factor and EPR signal amplitude for various shapes and gap numbers for the resonators containing a flat cell filled with water were examined numerically. This allowed finding the geometry that yields the maximum EPR signal intensity. Several X-band resonators were built in order to verify the results obtained theoretically. The experiments confirmed the ability of a novel resonant structure to accommodate a flat cell filled with an aqueous sample. It has been found that the optimum aqueous sample volume for the X-band rectangular loop-gap resonator equals 16 mm3. For a saturable aqueous sample this gives a fourfold improvement in the S/N ratio over the circular 1 mm i.d. loop-gap resonator equipped with 0.6 mm i.d. capillary.
已开发出一种用于扁平样品池的新型矩形环形间隙谐振器。假设仅存在磁场z分量，求解了具有两个、四个、六个和八个间隙的谐振器的麦克斯韦方程。对所得公式进行数值求解，以得到谐振器横截面上的电场和磁场分布。谐振器中心存在电场节点平面，这使得在电子顺磁共振（EPR）测量中可以使用扁平样品池而非毛细管。利用所获得的场分布，对包含充满水的扁平样品池的谐振器的各种形状和间隙数量的品质因数和EPR信号幅度进行了数值研究。这使得能够找到产生最大EPR信号强度的几何结构。为了验证理论结果，制作了几个X波段谐振器。实验证实了这种新型谐振结构容纳充满水性样品的扁平样品池的能力。已发现，X波段矩形环形间隙谐振器的最佳水性样品体积为16立方毫米。对于可饱和水性样品，与配备内径0.6毫米毛细管的内径1毫米圆形环形间隙谐振器相比，其信噪比提高了四倍。
