Such frequency-swept EPR systems is to ensure a (near-)constant sensitivity over wide sweep ranges. The bulky electromagnets and microwave parts are replaced with smaller permanent magnets and miniaturized electronic components capable of sweeping
This vision requires a complete redesign of the EPR spectrometer, in which Interest, removing the limitations of current resonator-based techniques. Sensor that can be immersed in, attached to, or embedded in a sample of In the optimum case, such a spectrometer would consist of a single Powerful technique in science, industry, and even consumer applications,Īccess to portable, cost-effective, and easy-to-operate EPR sensors is ≈ EUR 50 000 for benchtop devices up to well over EUR 1 000 000įor high-end spectrometers.
Sales prices of EPR spectrometers range from High-end spectrometers are available at much higher frequencies, operatingĪt X (9 GHz), Q (36 GHz), and W (94 GHz) bands up to even higher frequencies ( ∼ 263 GHz). While the former are limited to X-band operation, Relatively bulky, having typical dimensions ranging from several tens of centimeters for smaller benchtop X-band systems to several meters for higher-resolution research spectrometers. In standard CW (CW-EPR) operation, the magnetic field is modulated, enabling lock-in detection. To achieve the resonanceĬondition, an external magnetic field B 0 is swept linearly and continuously, while the MW frequency is kept constant due to the very lowīandwidth of the resonator, as dictated by the high Q employed to increase the SNR. The response of the magnetic susceptibility of the sample isĭetected via the reflected MW using an MW bridge. Spectrometers) to the magnetic moments of the unpaired electron spins of the Magnetic field component of the MW ( ∼ 9.4 GHz in X-band In conventional continuous-wave (CW) EPR spectrometers, a microwave (MW) cavity resonator with a high-quality factor ( Q) is used to enhance the signal-to-noise ratio (SNR) and the resolution. Vinck, 2007) in biological samples, in semiconductors, and during chemical reactions for assignment of the electronic and atomic structure of Quantification of paramagnetic centers (Eaton et al.,Ģ010) in, e.g., chemical analyses or quality control, the identification andĢ017), paramagnetic defects (Brodsky and Title, 1969),Īnd transition metal ion states (Van Doorslaer and Considering currently available technology, the frequency sweep range may be extended to 320 MHz, indicating that RS-EPRoC shows great promise for future sensitivity enhancements in theĮlectron paramagnetic resonance (EPR) spectroscopy is a widespread analytical tool for studying species with unpaired electrons relevant inĬhemistry, physics, biology, and medicine. Of a micrometer-scale BDPA sample can be transformed into the corresponding absorption EPR signals with high precision. The resulting time-domain RS-EPRoC signals Rapid-scan EPR (RS-EPRoC) experiments are performed by sweeping the frequency of the EPRoC VCO array with up to 400 THz s −1, corresponding to a field sweep rate of 14 kT s −1. Very high agility and near-constant sensitivity. Striking advantage of the VCO-based approach is the possibility of replacing the conventionally used magnetic field sweeps with frequency sweeps with MW resonator, VCO-based EPRoC detectors use an array of injection-locked VCOs, each incorporating a miniaturized planar coil as a combined microwave source and detector. Improve sensitivity compared to the continuous-wave regime. Rapid-scan EPR experiments with a comparatively simple experimental setup to The amplitude-sensitive mode of detection can be used to perform very fast More specifically, it is demonstrated that with a VCO-based EPRoC detector, Voltage-controlled oscillator (VCO)-based EPR-on-a-Chip (EPRoC) detectors are discussed, which have recently gained interest in the EPR community. Their application to dedicated lab environments. Common EPR spectrometers use electromagnets and microwave (MW) resonators, limiting
Scientific fields, including materials science and the life sciences. Method of choice to investigate and quantify paramagnetic species in many Electron paramagnetic resonance (EPR) spectroscopy is the