@article{oai:repo.qst.go.jp:00043879,
 author = {Hirata, Hiroshi and Ono, Mitsuhiro and et.al and 小野 光弘},
 issue = {2},
 journal = {Journal of Magnetic Resonance},
 month = {Oct},
 note = {A frequency modulation (FM) method was developed to measure electron paramagnetic resonace (EPR) absorption. The firstderivative spectrum of 1, 1-dipheny1-2-picrylhydrazy1 (DPPH) power was measured with this FM method. Frequency modulation of up to 1.6 MHz (peak-to-peak) was achieved at microwave carrier frequency of 1.1 GHz. This corresponds to a magnetic field modulation of 57 muT (peak-to-peak) at 40.3mT. By using a tunable microwave resonator and automatic control systems, we achieved a practical continuous-wave (CW) EPR spectrometer that incorporates the FM method. In the present experiments, the EPR signal intensity was proportional to the magnitude of frequency modulation. The background signal at the modulation frequency (1kHz) for EPR detection was also proportional to the magnitude of frequency modulation. An automatic matching control (AMC) system reduced the amplitude of noise in microwave detection and improve the baseline stability. Distortion of the spectral lineshape was seen when the spectrometer settings were not approriate, e.g., with a lack of the open-loop gain in automatic tuning control (ATC). FM is an alternative to field modulation when the side-effect of field modulation is detrimental for EPR detection. The present spectroscopic technique based on the FM scheme is useful for measuring the first derivative with respect to the microwave frequency in investigations of electron-spin-related phenomena.},
 pages = {233--241},
 title = {Detection of electron paramagnetic resonance absorption using frequency modulation},
 volume = {164},
 year = {2003}
}