Applications of EPR and ENDOR Spectrum Simulations in Radiation Research

Erickson, Roland; Lund, Anders

doi:10.1007/978-3-319-09216-4_19

Cited by 5 publications

(7 citation statements)

References 162 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The spectra were generated using a free EasySpin example “trifluoromethyl; CF 3 radical in gas matrix at low temperature”. In this example, the method of calculation was chosen as the second-order perturbation and further changing the method by “matrix” to exact diagonalization . The second-order computation is also given in Figure b for completeness.…”

Section: Theoretical Sectionmentioning

confidence: 99%

See 1 more Smart Citation

Rotation Dynamics Do Not Determine the Unexpected Isotropy of Methyl Radical EPR Spectra

et al. 2015

View full text Add to dashboard Cite

A simple first-principles electronic structure computation, further qc (quantum chemistry) computation, of the methyl radical gives three equal hf (hyperfine) couplings for the three protons with the unpaired electron. The corresponding dipolar tensors were notably rhombic and had different orientations and regular magnitude components, as they should, but what the overall A-tensor was seen by the electron spin is a different story! The final g = (2.002993, 2.002993, 2.002231) tensor and the hf coupling results obtained in vacuum, at the B3LYP/EPRIII level of theory clearly indicate that in particular the above A = (-65.19, -65.19, 62.54) MHz tensor was axial to a first approximation without considering any rotational dynamics for the CH3. This approximation was not applicable, however, for the trifluoromethyl CF3 radical, a heavier and nonplanar rotor with very anisotropic hf coupling, used here for comparison. Finally, a derivation is presented explaining why there is actually no need for the CH3 radicals to consider additional rotational dynamics in order for the electron to obtain an axially symmetric hf (hyperfine) tensor by considering the simultaneous dipolar couplings of the three protons. An additional consequence is an almost isotropic A-tensor for the electron spin of the CH3 radical. To the best of our knowledge, this point has not been discussed in the literature before. The unexpected isotropy of the EPR parameters of CH3 was solely attributed to the rotational dynamics and was not clearly separated from the overall symmetry of the species. The present theoretical results allowed a first explanation of the "forbidden" satellite lines in the CH3 EPR spectrum. The satellites are a fingerprint of the radical rotation, helping thus in distinguishing the CH3 reorientation from quantum rotation at very low temperatures.

show abstract

Section: Theoretical Sectionmentioning

confidence: 99%

“…The microwave resonance frequency was 9.27 GHz. “ A ” principal angles: (0, β, 0), (0, β, 2π/3), (0, β, – 2π/3), where β = −17.8°, as it was suggested by Prof. Anders Lund . (b) Second-order computation for the CF 3 radical with the same parameters as in (a) by the EasySpin software.…”

Section: Theoretical Sectionmentioning

confidence: 99%

Rotation Dynamics Do Not Determine the Unexpected Isotropy of Methyl Radical EPR Spectra

et al. 2015

View full text Add to dashboard Cite

show abstract

“…The combined EPR spectrum of L-alanine Harwell pellets and a MgO:Mn 2+ single crystal used as a reference standard is shown in figure 3. Actually, diluted Mn 2+ paramagnetic ions, with S = 5/2 and I = 5/2 have been widely used as reference signals in quantitative EPR analysis [4][5][6]9]. They show a sextet of equally spaced (by ~9 mT) lines due to the hyperfine coupling between electronic and nuclear spins.…”

Section: Epr Characterization Of L-alanine Pellets Irradiatied With G...mentioning

confidence: 99%

“…Electron paramagnetic resonance (EPR, also named electron spin resonance-ESR) is a non-destructive technique which has been widely used to estimate doses of ionizing radiation in multiple situations such as radiological emergencies [1,2], medical therapies [3], industrial processes, dating of archeological or paleontological samples, etc [4]. The principle of detection of EPR dosimeters consists on the ability of detecting and quantifying point paramagnetic defects, usually free radicals, that are created by the ionizing radiation (photons, neutrons, electrons or other particles) incident on an adequate material.…”

Section: Introductionmentioning

confidence: 99%

A dual natural lithium formate/L-alanine EPR dosimeter for a mixed radiation field in a boron neutron capture therapy irradiation facility

Alejandro

Longhino

Álvarez

et al. 2020

J. Phys. D: Appl. Phys.

View full text Add to dashboard Cite

Standard commercial L-alanine pellets and specially prepared natural lithium formate monohydrate powder samples of specific granulometry were irradiated in a 60 Co gamma-ray irradiation plant and in the mixed field (thermal neutrons and gamma photons) of a boron neutron capture therapy (BNCT) experimental facility. The γ-doses applied with the 60 Co source range from 0.1 to 50 kGy, while those in the BNCT facility go from ~7 Gy to 150 Gy. The thermal neutron fluences range from 10 12 neutrons cm −2 to 2 10 13 neutrons cm −2 . The irradiation of materials promotes the creation of stable electronic defects (generally free radicals) which constitute paramagnetic centers that can be detected and quantified by electron paramagnetic resonance (EPR). After irradiation, the EPR characterization of the samples was performed by determining the EPR intensity of the spectrum relative to a reference standard constituted by Mn 2+ impurities diluted into a MgO single crystal. As expected, L-alanine has revealed to be largely insensitive to thermal neutrons fluence in the investigated range. On the contrary, it is shown that the EPR intensity of irradiated natural lithium formate monohydrate powders is clearly sensitive to thermal neutrons and has a linear dependence with the γ-dose. We propose a dual dosimeter by combining L-alanine pellets and formate powders that would allow to determine the γ-dose and thermal neutron fluence in a selected position of the BNCT irradiation facility. Moreover, we demonstrate that the 6 Li enrichment that has been proposed in the literature to enhance the performance of lithium-based EPR dosimeters is not crucial in our case. Instead, the natural isotopic abundance of lithium is large enough to obtain a satisfactory sensibility to thermal neutrons in our BNCT facility for fluencies >10 12 neutrons cm −2 .

show abstract

“…Electron Paramagnetic Resonance (EPR) spectroscopy, also known as electron spin resonance (ESR) spectroscopy, has proven itself to be a valuable tool in several branches of science due to its exceptional performance and sensitivity (Lund and Shiotani 2016; Eaton et al 2010). It is a non-destructive spectroscopic technique used for retrospective dosimetry (Ainsbury et al 2010).…”

Section: Introductionmentioning

confidence: 99%

EPR Investigation of Temporal and Thermal Stability of Irradiated Sweeteners

Abdelrahman

Hayes

2022

Health Physics

View full text Add to dashboard Cite

Electron paramagnetic resonance was used to study the dosimetric properties of commercial sweeteners (sucrose, saccharin, and stevia). The results concluded that sugar has dosimetric properties of interest, which makes it suitable for dose reconstruction, emergency response, and nuclear forensics applications. The radiation dose response was investigated by irradiating samples up to 10 Gy and found to be linear. The post-irradiation stability of samples was observed to be useful for the intended applications. The results showed that the post-irradiation intensities vary from one sample to another, with the general trend demonstrating a small increase in intensities shortly after irradiation followed by an approximately constant leveling out. Finally, the effect of isochronal annealing was studied by heating samples to various temperatures. The results showed an overall stable behavior of the signal below melting temperature.

show abstract

Applications of EPR and ENDOR Spectrum Simulations in Radiation Research

Cited by 5 publications

References 162 publications

Rotation Dynamics Do Not Determine the Unexpected Isotropy of Methyl Radical EPR Spectra

Rotation Dynamics Do Not Determine the Unexpected Isotropy of Methyl Radical EPR Spectra

A dual natural lithium formate/L-alanine EPR dosimeter for a mixed radiation field in a boron neutron capture therapy irradiation facility

EPR Investigation of Temporal and Thermal Stability of Irradiated Sweeteners

Contact Info

Product

Resources

About