Rapid‐Scan Electron Paramagnetic Resonance

Comparison of Continuous Wave and Rapid Scan X-band Electron Paramagnetic Resonance of Irradiated Clipped Fingernails

“…For the same extent of power saturation, the ability to apply higher microwave power without saturation of the signal results in a stronger EPR signal in the rapid scan experiment, as shown in Figure 1. The region of the power saturation curve in which signal increases linearly with B 1 extends to higher B 1 as the scan rate increases, with some limitations that depend on T 1 and T 2 (18) . The shape of the rapid scan power saturation curve (Fig.…”

“…Following down-conversion of the microwave signal in a double-balanced mixer, the rapid scan EPR signals were digitized in a Bruker SpecJet II. The use of a dielectric resonator facilitates rapid magnetic field scans (18) . The dielectric resonator Q (~9000) is somewhat higher than of the SHQ resonator, but the EPR signal from the dielectric resonator is transmitted to the detection system through 80 cm of lossy semirigid coaxial cable, whereas the EMX system is fully constructed of low-loss waveguide, so the potential increase in signal intensity due to the higher Q of the dielectric resonator is offset by the losses in the coax.…”

“…A key feature of the rapid scan experiment is that the magnetic field is scanned through resonance thousands of times per second, which alleviates the need to select a modulation amplitude that is small relative to signal linewidth and permits detection of the full signal amplitude in every pass through the spectrum. Higher microwave B 1 can be used for rapid scan than for conventional CW, which also improves S/N (18) .…”

“…X-band vs. Qband (16,17) , microwave power, etc., for ascertaining the radiation dose). The purpose of this study is solely to compare two EPR data acquisition methods, conventional continuous wave (CW) and the newly developed rapid scan method (18) , for irradiated clipped fingernail samples. Comparisons in this study were performed at X-band in standard 4 mm tubes because the sample tube size was convenient.…”

“…Rapid scan EPR methodology was explained in references (18) and (19) . The method has provided substantially improved signal-to-noise (S/N) relative to CW EPR for a wide range of samples including paramagnetic defects in solids (20) , the radiationinduced defects in teeth (21) , defects in gamma irradiated solids (22) and immobilized organic radicals (23) .…”