Microwave frequency modulation in CW EPR at W-band using a loop-gap resonator
Microwave frequency modulation in CW EPR at W-band using a loop-gap resonator
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DOI：
10.1016/j.jmr.2007.01.002
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发表时间：
2007-04-01
影响因子：
2.2
通讯作者：
Strangeway, Robert A.
中科院分区：
文献类型：
--
作者：
Hyde, James S.;Froncisz, Wojciech;Strangeway, Robert A.
环隙谐振器（LGR）技术已扩展到w波段（94 GHz）。多臂q波段（35 GHz） EPR电桥的一个输出通过与59 GHz混合转换到w波段用于样品辐照；同样，将EPR信号转译回q波段进行检测。还开发了一种适用于100khz场调制的圆柱形TE011模式谐振腔。结果使用微波频率调制（FM）在50千赫作为替代磁场调制描述。调频是通过调制一个耦合到59 GHz振荡器的变容管来实现的。在过调制和y(2)H(1)(2)T(1)T(2) < 1的条件下进行了灵敏度的自旋标记研究。通过锁相检测，在基频调制频率（50 kHz）和二、三次谐波（100和150 kHz）下获得了吸收和色散的EPR光谱。源噪声在一阶谐波谱中是有害的，而在二阶和三阶谐波谱中是很低的。一谐波微波调频通过自旋转变为二、三次谐波微波调制，满足“调制转移”原理。带样品的LGR的加载q值为90（即3db点之间约1 GHz的带宽），计算出1 W入射功率下谐振腔效率参数为9.3 G，频率偏差为11.3 MHz p-p，相当于4 G的场调制幅值。(C) 2007年Elsevier Inc.出版
Loop-gap resonator (LGR) technology has been extended to W-band (94 GHz). One output of a multiarm Q-band (35 GHz) EPR bridge was translated to W-band for sample irradiation by mixing with 59 GHz; similarly, the EPR signal was translated back to Q-band for detection. A cavity resonant in the cylindrical TE011 mode suitable for use with 100 kHz field modulation has also been developed. Results using microwave frequency modulation (FM) at 50 kHz as an alternative to magnetic field modulation are described. FM was accomplished by modulating a varactor coupled to the 59 GHz oscillator. A spin-label study of sensitivity was performed under conditions of overmodulation and y(2)H(1)(2)T(1)T(2), < 1. EPR spectra were obtained, both absorption and dispersion, by lock-in detection at the fundamental modulation frequency (50 kHz), and also at the second and third harmonics (100 and 150 kHz). Source noise was deleterious in first harmonic spectra, but was very low in second and third harmonic spectra. First harmonic microwave FM was transferred to microwave modulation at second and third harmonics by the spins, thus satisfying the "transfer of modulation" principle. The loaded Q-value of the LGR with sample was 90 (i.e., a bandwidth between 3 dB points of about 1 GHz), the resonator efficiency parameter was calculated to be 9.3 G at one W incident power, and the frequency deviation was 11.3 MHz p-p, which is equivalent to a field modulation amplitude of 4 G. 14, band EPR using an LGR is a favorable configuration for microwave FM experiments. (C) 2007 Published by Elsevier Inc.