Electron Spin Resonance Spectrometer Research Articles

Estimation of gamma radiation effects on the polypropylene (PP) films at various doses

Medical polypropylene (PP) is exposed to ionizing radiation during the sterilization process before its use for medical purposes. Herein, the raw and manufactured PP were prepared as polymeric films with the same specifications. Then, raw and manufactured PP were irradiated by different doses of gamma rays in the air to discover the gamma radiation effects on the prepared films. The gamma doses were 25, 50, 75, 100, and 200 kGy. The irradiated raw and manufactured PP were characterized by different analytical techniques such as Electron Spin Resonance Spectrometer (ESR), Fourier Transform Infrared Spectroscopy (FTIR), X-ray diffraction (XRD), Thermogravimetric Analysis (TGA), Differential Scanning Calorimetry (DSC), Scanning Electron Microscopy (SEM), Energy Dispersive X-ray (EDX), and mechanical properties. The FTIR study indicated the presence of a new band at a low gamma dose for both cases. The crystallinity percentages of both raw and manufactured PP gradually reduced when the gamma doses increased. The thermal stability of films decreased by increasing the gamma doses. Raising the gamma dosages resulted in a decrease in the mechanical characteristics of raw PP and manufactured PP such as elongation @ break, elastic modulus, and tensile strength.

Compact Electron Paramagnetic Resonance on a Chip Spectrometer Using a Single Sided Permanent Magnet.

Electron paramagnetic resonance (EPR) spectroscopy provides information about the physical and chemical properties of materials by detecting paramagnetic states. Conventional EPR measurements are performed in high Q resonator using large electromagnets which limits the available space for operando experiments. Here we present a solution toward a portable EPR sensor based on the combination of the EPR-on-a-Chip (EPRoC) and a single-sided permanent magnet. This device can be placed directly into the sample environment (i.e., catalytic reaction vessels, ultrahigh vacuum deposition chambers, aqueous environments, etc.) to conduct in situ and operando measurements. The EPRoC reported herein is comprised of an array of 14 voltage-controlled oscillator (VCO) coils oscillating at 7 GHz. By using a single grain of crystalline BDPA, EPR measurements at different positions of the magnet with respect to the VCO array were performed. It was possible to create a 2D spatial map of a 1.5 mm × 5 mm region of the magnetic field with 50 μm resolution. This allowed for the determination of the magnetic field intensity and homogeneity, which are found to be 254.69 mT and 700 ppm, respectively. The magnetic field was mapped also along the vertical direction using a thin film a-Si layer. The EPRoC and permanent magnet were combined to form a miniaturized EPR spectrometer to perform experiments on tempol (4-hydroxy-2,2,6,6-teramethylpiperidin-1-oxyl) dissolved in an 80% glycerol and 20% water solution. It was possible to determine the molecular tumbling correlation time and to establish a calibration procedure to quantify the number of spins within the sample.

Effect of Water Immersion on the Reoxidation Capacity of Coal with Different Secondary Oxidation Degrees

ABSTRACT Water accumulation and secondary oxidation of residual coal are commonly encountered in goaf, which can endanger the safety of coal mines. Both factors can affect the oxidation capacity of coal. Hence, it is essential to investigate the reoxidation capacity of residual coal with secondary oxidation in goaf after water immersion. This helps reveal the influence of different degrees of water immersion on coal samples with varying degrees of secondary oxidation. In this study, a programmed temperature system was used to examine the re-burning capacity of bituminous coal under the combined effects of secondary oxidation and water immersion. An electron spin resonance spectrometer was employed to examine the alteration in free radicals present for analyzing the evolution of microscopic groups of coal. According to the research results, under the same soaking conditions, an increase in secondary oxidation temperature leads to a decrease in the reoxidation capacity of coal. During re-oxidation, the immersion in water accelerates the process in bituminous coal with a secondary oxidation temperature of 120°C, while it has a certain inhibitory effect on coal samples with a secondary oxidation temperature of 180°C. This research lays a theoretical foundation for comprehending the re-oxidation of coal under complex conditions.

Reduction Removal of Cr(VI) Using Oxalic Acid With MOF‐525(Fe) as Catalyst: Performance and Mechanism

ABSTRACTHexavalent chromium (Cr(VI)) has attracted great considerations due to their high toxicity, teratogenicity, and carcinogenicity. In this study, four Zr‐MOFs were synthesized and used to comparative study their catalytic performances of oxalic acid (OA) for Cr(VI) removal. Results showed that the removal efficiency for Cr(VI) was reached 65.91%, 78.64%, 53.58%, and 96.32% by MOF‐525, MOF‐525(Co), MOF‐525(Zn), and MOF‐525(Fe) in the presence of OA when the initial Cr(VI) concentration was 100 mg·L−1, respectively. The single‐factor experiments for further improving the Cr(VI) removal by MOF‐525(Fe)/OA demonstrated that the optimal conditions were OA dosage of 790 mg·L−1, and MOF‐525(Fe) dosage of 500 mg·L−1 and pH of 2.0, and the MOF‐525(Fe)/OA system could be used to treat Cr(VI)‐containing wastewater at concentrations below 50 mg·L−1. Ionic strength studies indicated that Na+, K+, Mg2+, Cl−, and SO42− had little effect on the catalytic reduction of Cr(VI), while high concentrations of Ca2+ (0.10 and 0.25 mol·L−1), NO3− (0.25 mol·L−1), and PO43− (0.25 mol·L−1) had significant inhibition effects. The reusability experiments showed that the stability of MOF‐525(Fe) was excellent, and it could be used for potential applications. Based on the results of Fourier transform infrared spectroscopy (FTIR), X‐ray photoelectron spectroscopy (XPS), and Electron Paramagnetic Resonance spectrometer (EPR), the possible reduction mechanism of Cr(VI) by MOF‐525(Fe)/OA system was proposed as follows: The complexation of OA with Fe3+ was first complexed to produce Fe2+ and CO2•−, then Cr(VI) was combined with Zr–O and Fe–O clusters in MOF‐525(Fe) to obtain activation energy, and the reduction ability was enhanced at the same time; finally, Cr(VI) obtained electrons from CO2•− and was sequentially reduced as Cr(V) and Cr(III).

Calculation of π Using a Molecular Electron Spin Qubit Implemented by Pulsed Electron Paramagnetic Resonance.

The present letter demonstrates a simple method to characterize the molecular electron spin qubits, for which a large number of chemical compounds with non-zero spin have been proposed. The method is based on calculating the value of π using a one-qubit protocol based on obtaining and processing Rabi oscillations. It was implemented using a model system of a Finland trityl radical with an electron spin S = 1/2 and a pulsed electron paramagnetic resonance spectrometer. As a result, the value of π was obtained with an accuracy of two decimal places, and an analysis of statistical and systematic errors was carried out.

Field-domain rapid-scan EPR at 240 GHz for studies of protein functional dynamics at room temperature

We present field-domain rapid-scan (RS) electron paramagnetic resonance (EPR) at 8.6T and 240GHz. To enable this technique, we upgraded a home-built EPR spectrometer with an FPGA-enabled digitizer and real-time processing software. The software leverages the Hilbert transform to recover the in-phase (I) and quadrature (Q) channels, and therefore the raw absorptive and dispersive signals, χ′ and χ′′, from their combined magnitude (I2+Q2). Averaging a magnitude is simpler than real-time coherent averaging and has the added benefit of permitting long-timescale signal averaging (up to at least 2.5×106 scans) because it eliminates the effects of source-receiver phase drift. Our rapid-scan (RS) EPR provides a signal-to-noise ratio that is approximately twice that of continuous wave (CW) EPR under the same experimental conditions, after scaling by the square root of acquisition time. We apply our RS EPR as an extension of the recently reported time-resolved Gd-Gd EPR (TiGGER) [Maity et al., 2023], which is able to monitor inter-residue distance changes during the photocycle of a photoresponsive protein through changes in the Gd-Gd dipolar couplings. RS, opposed to CW, returns field-swept spectra as a function of time with 10ms time resolution, and thus, adds a second dimension to the static field transients recorded by TiGGER. We were able to use RS TiGGER to track time-dependent and temperature-dependent kinetics of AsLOV2, a light-activated phototropin domain found in oats. The results presented here combine the benefits of RS EPR with the improved spectral resolution and sensitivity of Gd chelates at high magnetic fields. In the future, field-domain RS EPR at high magnetic fields may enable studies of other real-time kinetic processes with time resolutions that are otherwise difficult to access in the solution state.

Formation of persistent free radicals from epigallocatechin Gallate in tea processing and their implications on DNA damage and cell cytotoxicity

Tea is widely consumed in both beverages and food. Epigallocatechin gallate (EGCG) is the most crucial active ingredient in tea. Currently, knowledges on transformation processes of EGCG during tea processing are lacking. Understanding the chemical reactions of EGCG and its products during tea processing is important for assessing the safety of tea-containing food. Here, we revealed the formation of persistent free radicals (PFRs) from EGCG under the influence of heating and light irradiation, which was substantiated with evidence. These PFRs exhibited stability for >30 min in simulated gastric fluid. Furthermore, we observed potential effects of these PFRs on DNA damage and cell cytotoxicity in vitro. By combining electron paramagnetic resonance spectrometer with Fourier transform ion cyclotron resonance mass spectrometry, we elucidated the pathways involved in free radical formation. These findings are expected to contribute to a comprehensive understanding of free radical chemistry in tea-containing food.

Novel approach for emergency dosimetry: Investigations of screen protectors for smartphones by EPR spectroscopy

Screen protectors for smartphone are investigated in attempts for emergency dosimetry as for example in case of malicious attacks with radioactive sources or accidental overexposure. Electron Paramagnetic Resonance (EPR) measurements were carried out on six different types of screen protectors (SPs). The inter and intra batch variability of the EPR signals characteristics (sensitivity, stability, signal shape) were studied. Contrary to touch screen (De Angelis et al., 2015; Juniewicz et al., 2020), UVB exposure for SP is not a limiting confounding factor. All samples under irradiation exhibit same EPR signals. The nature of the radio-induced point defects was identified (HC1 and HC2) as well as their evolution according to dose. The linear dose response was studied in the 0–5 Gy dose range with a detection limit estimated of 750 mGy with a field deployable benchtop EPR spectrometer. Large variability of the dose response prevents presently from using universal calibration curve. Therefore, further work is needed to consider possible application for triage in the case of large-scale accidents scenarios.

Rational engineering β-Bi2O3/Bi2O2CO3 heterojunction photocatalyst from tetragonal BiOCl microrods displaying high photocatalytic performance

A tetragonal cylindrical Bi2O2CO3 self-assembled from nanosheets was formed in situ by interlayered substitution using BiOCl column as the precursor. The β-Bi2O3/Bi2O2CO3 heterojunction was synthesized then by calcining the as-formed Bi2O2CO3. The β-Bi2O3/Bi2O2CO3 showed excellent photocatalytic performance with k values (the apparent rate constants) were 0.1738 and 0.1162min−1, respectively, for degrading 50 mg/L Cr(VI) solution and 10 mg/L MO. Both free radical trapping and electron paramagnetic resonance spectrometer measurements proved that superoxide radical (O2−) was key active species photodegradation of Cr(VI) and MO. The photoluminescent spectroscopy and electrochemical impedance indicated that the β-Bi2O3/Bi2O2CO3 heterojunction had a high separation efficiency of photogenerated charge carriers. This work provides a simple anion exchange synthesis method, which will inspire many researchers to develop high-performance catalysts.

Enhancing radiation resistance of silicone rubber through the addition of polydopamine-modified cerium dioxide

With the widespread use of nuclear science and technology, slowing down the aging of polymers in a radiation environment has become a matter of great concern. In this work, cerium dioxide (CeO2) and CeO2 encapsulated with dopamine (PDA@CeO2) were selected as special fillers to prepare the silicone rubber (SR) composites, and their radiation resistance were investigated by comparing the mechanical properties and thermal performance before and after irradiation. The interfacial bridge formed by PDA results in a greater elongation at break for PDA@CeO2/SR5.0 (770.0 ± 33.6 %) than for CeO2/SR (686.0 ± 15.0 %). After irradiation with γ-rays, the retention of elongation at break of both CeO2/SR0.1 and PDA@CeO2/SR0.1 were larger than SR. Furthermore, PDA@CeO2/SR0.1 showed an impressive retention of 90.5 ± 2.7 % of the tensile strength retention after exposure to an absorbed dose of 200 kGy. The disparity in crosslink density prior to and following irradiation indicated that both CeO2 and PDA@CeO2 were efficacious in reducing radiation crosslinking within the SR. An electron paramagnetic resonance spectrometer and an ultraviolet lamp (UV-EPR) were used to observe in real time the free radical scavenging ability of CeO2 and PDA@CeO2 inside the SR. These results indicated that CeO2 and PDA@CeO2 was expected to prevent further chain reactions in silicone rubber by scavenging free radicals generated in SR, thus improving the radiation resistance of SR.

A continuous-wave and pulsed X-band electron spin resonance spectrometer operating in ultra-high vacuum for the study of low dimensional spin ensembles.

We report the development of a continuous-wave and pulsed X-band electron spin resonance (ESR) spectrometer for the study of spins on ordered surfaces down to cryogenic temperatures. The spectrometer operates in ultra-high vacuum and utilizes a half-wavelength microstrip line resonator realized using epitaxially grown copper films on single crystal Al2O3 substrates. The one-dimensional microstrip line resonator exhibits a quality factor of more than 200 at room temperature, close to the upper limit determined by radiation losses. The surface characterizations of the copper strip of the resonator by atomic force microscopy, low-energy electron diffraction, and scanning tunneling microscopy show that the surface is atomically clean, flat, and single crystalline. Measuring the ESR spectrum at 15K from a few nm thick molecular film of YPc2, we find a continuous-wave ESR sensitivity of 2.6 × 1011spins/G · Hz1/2, indicating that a signal-to-noise ratio of 3.9G · Hz1/2 is expected from a monolayer of YPc2 molecules. Advanced pulsed ESR experimental capabilities, including dynamical decoupling and electron-nuclear double resonance, are demonstrated using free radicals diluted in a glassy matrix.

Effects of dissolved organic matter from sludge pyrolysis biochar on the triclosan removal from contaminated soil

When sludge biochar (SC) prepared from sewage sludge was used to remove triclosan (TCS) from both aqueous solution and soil, the adsorption capacity increased with increasing pyrolysis temperature, while the degradation rate showed a different pattern, namely, SC-500 > SC-800 > SC-600 > SC-700. TCS degradation rate achieved nearly 100 % at 2 h with SC-500 used as a Fenton catalyst. Aromaticity of dissolved organic matter (DOM) was positively correlated with the degradation of TCS and adding homologous DOM solution shortened the equilibrium time of TCS degradation, while removing DOM from SC prolonged, compared to the original SC. The results of X-ray photoelectron spectroscopy (XPS) and electron paramagnetic resonance spectrometer (EPR) characterization indicated that SC-500 performed a stronger catalytic degradation ability due to the relatively high Fe2+ content to produce more ∙OH and SC-derived DOM act as an electron shuttle to promote other reactive oxidative species generation through two free radical pathways in the activation of H2O2 by Fe2+, which in turn promoted the degradation of TCS.

Protective effect of luteolin against oxidative stress‑mediated cell injury via enhancing antioxidant systems.

Physiological stress such as excessive reactive oxygen species (ROS) production may contribute normal fibroblasts activation into cancer‑associated fibroblasts, which serve a crucial role in certain types of cancer such as pancreatic, breast, liver and lung cancer. The present study aimed to examine the cytoprotective effects of luteolin (3',4',5,7‑tetrahydroxyflavone) against hydrogen peroxide (H2O2)‑generated oxidative stress in lung fibroblasts. To examine the effects of luteolin against H2O2‑induced damages, cell viability, sub‑G1 cell population, nuclear staining with Hoechst 33342, lipid peroxidation and comet assays were performed. To evaluate the effects of luteolin on the protein expression level of apoptosis, western blot assay was performed. To assess the antioxidant effects of luteolin, detection of ROS using H2DCFDA staining, O2‑ and ·OH using electron spin resonance spectrometer and antioxidant enzyme activity was performed. In a cell‑free chemical system, luteolin scavenges superoxide anion and hydroxyl radical generated by xanthine/xanthine oxidase and the Fenton reaction (FeSO4/H2O2). Furthermore, Chinese hamster lung fibroblasts (V79‑4) treated with H2O2 showed a significant increase in cellular ROS. Intracellular ROS levels and damage to cellular components such as lipids and DNA in H2O2‑treated cells were significantly decreased by luteolin pretreatment. Luteolin increased cell viability, which was impaired following H2O2 treatment and prevented H2O2‑mediated apoptosis. Luteolin suppressed active caspase‑9 and caspase‑3 levels while increasing Bcl‑2 expression and decreasing Bax protein levels. Additionally, luteolin restored levels of glutathione that was reduced in response to H2O2. Moreover, luteolin enhanced the activity and protein expressions of superoxide dismutase, catalase, glutathione peroxidase, and heme oxygenase‑1. Overall, these results indicated that luteolin inhibits H2O2‑mediated cellular damage by upregulating antioxidant enzymes.

Free radical production induced by visible light in live fruit flies

Visible light triggers free radical production in alive and intact Drosophila melanogaster. We exposed fruit flies to red (613–631 nm), green (515–535 nm), and blue (455–475 nm) light while we monitored changes in unpaired electron content with an electron spin resonance spectrometer (ESR/EPR). The immediate response to light is a rapid increase in spin content lasting approximately 10 s followed by a slower, linear increase for approximately 170 s. When the light is turned off, the spin population promptly decays with a similar time course, though never fully returning to baseline. The magnitude and time course of the spin production depends on the wavelength of the light. Initially, we surmised that eumelanin might be responsible for the spin change because of its documented ability for visible light absorption and its highly stable free radical content. To explore this, we utilized different fruit fly strains with varying eumelanin content and clarified the relation of melanin types with the spin response. Our findings revealed that flies with darker cuticle have at least three-fold more unpaired electrons than flies with yellow cuticle. However, to our surprise, the increase in unpaired electron population by light was not drastically different amongst the genotypes. This suggests that light-induced free radical production may not exclusively rely on the presence of black melanin, but may instead be dependent on light effects on quinone-based cuticular polymers.

Efficient removal of size-fractionated antibiotic resistance genes (ARGs) in WWTPs secondary effluent by vacuum ultraviolet (VUV) activated potassium peroxymonosulfate (PMS)

Antibiotic resistance genes (ARGs) and mobile genetic elements (MGEs) in secondary effluent from wastewater treatment plants (WWTPs) have a size-fractionated character and conventional processes have difficulties in removing ARGs and MGEs. Therefore, this study aimed to explore the removal efficiency, removal mechanism and regeneration potential of size-fractionated ARGs and MGEs by vacuum ultraviolet (VUV)-activated peroxymonosulfate (PMS) and ascertain their potential hosts in secondary effluent. The proportion of particle-associated (PA)-ARGs and PA-MGEs was 85.07 %, followed by free-living (FL) fraction (14.91 %) and cell-free (CF) fraction (0.02 %). More than 95.00 %∼99.99 % of ARGs and MGEs in PA- and CF- fractions were removed by VUV/PMS, but the average removal efficiency of FL-ARGs and FL-MGEs was 66.15 %. Compared to the regeneration potential of PA- and CF-ARGs and MGEs (0.02 < C/C0 < 5.27), the regeneration occurred mainly in FL-ARGs and FL-MGEs (0.08 < C/C0 < 24.06). ·OH was the dominant radical (16.810 × 10-6 mol/L) in VUV/PMS for the removal of size-fractionated ARGs and MGEs from the secondary effluent, while SO4-· (4.478 × 10-6 mol/L) played a supporting role in the system based on the quenching experiment, electron paramagnetic resonance spectrometer and probe experiments. Based on full-scale classification, conditionally rare or abundant taxa (CRAT) were the core potential hosts in PA-, FL- and CF- fractions, while rare taxa (RT) and conditionally rare taxa (CRT) potential hosts were more diverse in the three fractions. This study suggests that VUV/PMS can effectively remove size-fractionated ARGs and MGEs from secondary effluent and thereby obviously reduce their dissemination risk to receiving water bodies, providing technical support for the engineering application of VUV/PMS in full-scale WWTPs.

Designing unimolecular photoinitiator by installing NHPI esters along the TX backbone for acrylate photopolymerization and their applications in coatings and 3D printing

Developing efficient and long wavelength sensitive unimolecular photoinitiators (PIs) is still facing a great challenge. In this work, a series of thioxanthone-based N-hydroxyphthalimide esters (TX-NHPIEs) were synthesized by installing NHPIEs along the TX backbone and characterized. The investigated TX-NHPIEs have a 60 nm redshift and demonstrate sterling initiating efficiency for free radical photopolymerization (FRP) under LED@450 nm light irradiation compared with the commercialized isopropylthioxanthone (ITX). Real-time 1Hnuclear magnetic resonance (1H NMR), electron spin resonance (ESR), decarboxylation and gas chromatograph-mass spectrometer (GC–MS) experiments and density functional theory (DFT) reveal that TX-NHPIEs can generate one alkyl radical and one N-centered iminyl radical, which can initiate FRP directly and indirectly, respectively. In other words, TX-NHPIEs absorb one photon and can generate two active radicals, which break through the limitations of common PIs. TX-NHPIE-Cpe demonstrates the highest initiating efficiency, and its application in coatings and 3D printing was also studied, indicating TX-NHPIEs have broad potential applications in photopolymerization processes.

The study of dosimetric properties of sulfanilic acid in low radiation dose range using the ESR technique

The development of new dosimeters with good dosimetric properties is important for quality control in radiation applications. In this study, the potential of sulfanilic acid (C6H7NO3S) powder form, as a dosimeter in low-dose ionizing radiation (<30 Gy), was analyzed by an Electron Spin Resonance spectrometer (Bruker EMX-131 X-band). Gamma irradiations were performed at room temperature (290 K) using a 60Co gamma cell supplying a dose rate of 32 Gy/h and X photon irradiations at 6 and 18 MV energies were performed using a variant DHX model clinical linear accelerator (Linac) at a dose rate of 3 Gy/min. While unirradiated (control) sulfanilic acid exhibited no ESR signal, the irradiated sample showed a single-line ESR spectrum spread over a magnetic field range of 100 G, as shown in Figure 2. Variations of the peak heights with the sample mass irradiated at 2 Gy gamma dose were studied in the range of 130–330 mg. The ESR signal intensity observed at g-factor = 2.0053 of this compound is dependent on sample mass, so ∼250 mg was chosen at each step of the study. The paramagnetic center formed in the gamma-irradiated sulfanilic acid was followed over 50 days. The dose-response curves were given in the dose range from 0.05 to 10 Gy for the sample exposed to gamma radiation and for the sample exposed in the range of 0.05 Gy–30 Gy at 6 and 18 MV X-ray energies. The fitting values of the function that best describes dose-response curves are calculated. In the g value region, where the ESR signal was observed in the irradiated sample, the lowest dose value at which the signal could be read was 50 mGy, significantly different from the noise. With all these investigations, sulfanilic acid can be used to estimate gamma radiation dose within boundary conditions in medical applications.

Study of Photodegradation of Thiazion Dye Methylene Blue under Exposure to a Laser for Photodynamic Therapy

Purpose. To study the process of photodegradation of methylene blue under the influence of laser radiation with a wavelength of 660 nm, used for photodynamic therapy installations, for the formation of reactive oxygen species, in particular short-lived hydroxyl radicals, using electron paramagnetic resonance (EPR) spectroscopy.Methods. The residual concentration of methylene blue during photodegradation was determined using an HR2000 spectrometer. The formation of hydroxyl groups was detected using an EPR spectrometer SPINSCAN X.Results. Analysis of data on the photodegradation of methylene blue shows that under the influence of laser radiation with a wavelength of 660 nm, the structure of methylene blue is destroyed, manifested in the gradual discoloration of the dye solution. When trypaflavin is added to the solution, the rate of photodegradation of methylene blue slows down significantly. Analysis of ESR spectroscopy data shows that when methylene blue is exposed to a red laser, (OH’) radicals begin to intensively form in the solution. Their content increases significantly with increasing irradiation power.Conclusion. Irradiation of an aqueous solution of the thiazion dye methylene blue by a laser source with a power of 0.3÷1 W and a wavelength of 660 nm leads to its active photodegradation. The addition of trypaflavin leads to a slowdown in the process of photodegradation of methylene blue when irradiated with red light due to the consumption of part of the generated oxygen-containing radicals for the degradation of trypaflavin. According to EPR spectroscopy data using DMPO spin traps, it has been proven that when methylene blue is irradiated with a red laser, active formation of hydroxyl OH' radicals occurs. It was found that with increasing laser radiation intensity, the amount of generated hydroxyl radicals (OH') increases significantly. The presented results may contribute to the development of effective photosensitizers for photodynamic therapy of tumor tumors.

Simple and effective in situ sample illumination for electron paramagnetic resonance.

Illumination into an electron paramagnetic resonance (EPR) spectrometer is commonly carried out through the optical window, perpendicular to the sample and magnetic field. Here we show that significant improvements can be obtained by using the walls of the EPR tube as a light guide, with the light scattered only around the sample-containing area.

Design and Implementation of Integrated Dual-Mode Pulse and Continuous-Wave Electron Paramagnetic Resonance Spectrometers

Design and Implementation of Integrated Dual-Mode Pulse and Continuous-Wave Electron Paramagnetic Resonance Spectrometers