Hassan A K, Pardi L A, Krzystek J, Sienkiewicz A, Goy P, Rohrer M, Brunel L C
Center for Interdisciplinary Magnetic Resonance, National High Magnetic Field Laboratory, Florida State University, 1800 E. Paul Dirac Drive, Tallahassee, Florida 32310, USA.
J Magn Reson. 2000 Feb;142(2):300-12. doi: 10.1006/jmre.1999.1952.
We report methodology that combines an ultrawide band multifrequency microwave system with technology of high magnetic fields for solving challenging problems in electron magnetic resonance (EMR) spectroscopy. This strategy has been made possible due to a novel EMR facility operating in an exceptionally wide range of microwave frequencies of 24 GHz to 3 THz, at magnetic fields up to 17 T, and in the temperature range of 1.6 to 330 K. The basic configuration of the multifrequency system works in a transmission mode and employs oversized cylindrical waveguides for routing the microwave power. A wide-band, low-noise, liquid helium cooled (4.2 K) InSb bolometer is used for signal detection. This approach results in an extremely wide-band performance, thus making it possible to employ a variety of solid-state millimeter and submillimeter microwave sources in combination with a far infrared laser microwave source for performing multifrequency EMR experiments. A complexity of resonant structures and related technical problems such as microphonics at high magnetic fields is virtually eliminated. The system is simple, yet sensitive, and has been revealed to be extremely advantageous while solving such problems as observation of AFMR transitions in spin-ordered systems, g-factor resolution enhancement in complex organic radicals, and resonance signal detection in EMR-silent spin systems having integer spin and large zero field splitting. A technical description of the multifrequency high-field EMR facility is presented and results of its performance tests are given. The potential utility of using the multifrequency high-field methodology in EMR studies is illustrated with selected examples of its recent applications.
我们报告了一种方法，该方法将超宽带多频微波系统与高磁场技术相结合，以解决电子磁共振（EMR）光谱学中的挑战性问题。由于一种新型的EMR设备，这种策略得以实现，该设备可在24 GHz至3 THz的超宽微波频率范围内、高达17 T的磁场以及1.6至330 K的温度范围内运行。多频系统的基本配置工作在传输模式，并采用超大尺寸的圆柱形波导来传输微波功率。一个宽带、低噪声、液氦冷却（4.2 K）的InSb测辐射热计用于信号检测。这种方法带来了极宽的带宽性能，从而使得可以将各种固态毫米波和亚毫米波微波源与远红外激光微波源结合使用，以进行多频EMR实验。共振结构的复杂性以及诸如高磁场下的颤噪效应等相关技术问题实际上被消除了。该系统简单但灵敏，并且在解决诸如自旋有序系统中AFMR跃迁的观测、复杂有机自由基中g因子分辨率的提高以及具有整数自旋和大零场分裂的EMR沉默自旋系统中的共振信号检测等问题时，已被证明具有极大的优势。本文介绍了多频高场EMR设备的技术描述，并给出了其性能测试结果。通过其近期应用的选定示例，说明了在EMR研究中使用多频高场方法的潜在效用。
