Continuous Wave EPR of Radicals in Solids

Lund, Anders; Liu, Wei

doi:10.1007/978-1-4757-5166-6_1

Cited by 4 publications

(5 citation statements)

References 64 publications

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“…Electron paramagnetic resonance (EPR) spectroscopy − of open-shell transition-metal complexes is an important spectroscopic tool in a variety of research fields, ranging from a mapping of defects in solid-state materials and surfaces (e.g., in heterogeneous catalysis) , via studies of single-molecule magnets − to those of paramagnetic metalloenzyme sites. − Use of quantum-chemical methods to aid the evaluation and interpretation of EPR parameters, or to elucidate the structure of new, sometimes exotic, species based on EPR experiments has seen tremendous developments over the past 20 years. ,− Calculations of molecular properties such as the electronic g -tensor and hyperfine coupling (HFC) A -tensors are, however, still a considerable challenge for quantum-chemical methods due to the large sensitivity of these intrinsic parameters to the molecular structure as well as to relativistic and environmental effects . Due to the spin–orbit-dominated nature of g -tensors and the dependence of HFCs on spin-density distributions near the nuclei, spin–orbit (SO) and scalar relativistic effects range from important to crucial in this context, and they grow toward the lower regions of the Periodic Table.…”

Section: Introductionmentioning

confidence: 99%

Four-Component Relativistic Density Functional Theory Calculations of EPRg- and Hyperfine-Coupling Tensors Using Hybrid Functionals: Validation on Transition-Metal Complexes with Large Tensor Anisotropies and Higher-Order Spin–Orbit Effects

et al. 2015

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The four-component matrix Dirac-Kohn-Sham (mDKS) implementation of EPR g-and hyperfine A-tensor calculations within a restricted kinetic balance framework in the ReSpect code has been extended to hybrid functionals. The methodology is validated for an extended set of small 4d 1 and 5d 1 [MEXn] q systems, and for a series of larger Ir(II) and Pt(III) d 7 complexes (S=1/2) with particularly large g-tensor anisotropies. Different density functionals (PBE, BP86, B3LYP-xHF, PBE0-xHF) with variable exact-exchange admixture x (ranging from 0% to 50%) have been evaluated, and the influence of structure and basis set has been examined. Notably, hybrid functionals with exact-exchange admixture of about 40% provide the best agreement with experiment and clearly outperform the generalized-gradient approximation (GGA) functionals, in particular for the hyperfine couplings. Comparison with computations at the one-component second-order perturbational level within the DouglasKroll-Hess framework (1c-DKH), and a scaling of the speed of light at the four-component mDKS level, provide insight into the importance of higher-order relativistic effects for both properties. In the more extreme cases of some iridium(II) and platinum(III) complexes, the widely used leading-order perturbational treatment of SO effects in EPR calculations fails to reproduce not only the magnitude but also the sign of certain g-shift components (with the contribution of higher-order SO effects amounting to several hundreds of ppt in 5d complexes). The four-component hybrid mDKS calculations perform very well, giving overall good agreement with the experimental data.

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Section: Introductionmentioning

confidence: 99%

Four-Component Relativistic Density Functional Theory Calculations of EPRg- and Hyperfine-Coupling Tensors Using Hybrid Functionals: Validation on Transition-Metal Complexes with Large Tensor Anisotropies and Higher-Order Spin–Orbit Effects

et al. 2015

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“…EPR quantitation of the radiationinduced radicals makes it possible to measure the radiation dose absorbed by the irradiated material. Due to this ability, EPR dosimetry has developed into one of the most widely used and recognized applications in the universe of EPR (Lund and Shiotani, 2003). It has been used in industrial irradiations, medicine, environmental sciences, geology, and archaeology.…”

Section: Introductionmentioning

confidence: 99%

EPR dosimetry with tooth enamel: A review

Fattibene

Callens

2010

Applied Radiation and Isotopes

212

160

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When tooth enamel is exposed to ionizing radiation, radicals are formed that can be detected using Electron Paramagnetic Resonance (EPR) techniques. EPR dosimetry using tooth enamel is based on the (presumed) correlation between the intensity or amplitude of some of the radiation-induced signals with the dose absorbed in the enamel. In the present paper a critical review is given of this widely applied dosimetric method.The first part of the paper is quite fundamental and deals with the main properties of tooth enamel and several of its model systems (e.g., synthetic apatites). Considerable attention is also devoted to the numerous radiation-induced and native EPR signals, and the radicals responsible for them. The relevant EPR detection, identification and spectrum analysing methods are reviewed from a general point of view. Finally, the need for solid state modelling and the linearity of the dose response are investigated.The second part is devoted to the practical implementation of EPR dosimetry using enamel. It concerns the preparation of samples, specific irradiation problems, spectrum acquisition and it is described how the dosimetric signal intensity and dose can be retrieved from the EPR spectra. Special attention is paid to the energy dependence of the EPR response and to sources of uncertainties. Results of and problems encountered in international intercomparisons and epidemiological studies are also dealt with.In the final chapter the future of EPR dosimetry with tooth enamel is analysed.

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“…47 is Holmes and Weiss (104 ). Enormous fields of science have developed from this beginning (105,106 ). EPR is used to determine whether foodstuffs have been irradiated to preserve them.…”

Section: Radicals Created By Radiationmentioning

confidence: 99%

“…The anisotropy of nitroxyl radical EPR, explored by modern CW and pulsed EPR, has revealed much of the current understanding of molecular motion in liquids and glasses via many experiments in the Freed lab (33). Calculation of EPR parameters is being performed at a high level of sophistication (106,120) and has been incorporated into commercially available computational programs, such as Gaussian (Wallingford, CT). The articles in Rudowicz et al (121) and Kawamori et al (122) give an indication of the scope of applications of modern EPR to physics and magnetism, materials sciences, chemical reactions, environmental sciences, biology and life sciences, medical sciences, geology, and dosimetry, using CW, pulsed, and multiple-frequency EPR.…”

Section: Summary Perspectivementioning

confidence: 99%

EPR at work: Part 1

Hyde

2006

Concepts Magnetic Resonance

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Continuous Wave EPR of Radicals in Solids

Cited by 4 publications

References 64 publications

Four-Component Relativistic Density Functional Theory Calculations of EPRg- and Hyperfine-Coupling Tensors Using Hybrid Functionals: Validation on Transition-Metal Complexes with Large Tensor Anisotropies and Higher-Order Spin–Orbit Effects

Four-Component Relativistic Density Functional Theory Calculations of EPRg- and Hyperfine-Coupling Tensors Using Hybrid Functionals: Validation on Transition-Metal Complexes with Large Tensor Anisotropies and Higher-Order Spin–Orbit Effects

EPR dosimetry with tooth enamel: A review

EPR at work: Part 1

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