EPR and UV spectrometry investigation of sucrose irradiated with carbon particles

Solid state/EPR (SS/EPR) dosimeters of carbon ions irradiated sucrose are studied with EPR, and their water solutions – with UV spectroscopy. Doses between 20 and 200 Gy are used with linear energy transfer (LET) values for carbon ions of 63, 77, 96 and 230 keV μm^?1. After irradiation all samples show typical for irradiated sucrose EPR and UV spectra. The obtained data are compared with those previously reported for nitrogen particles and gamma rays irradiated sucrose. The identical shape of both the EPR and UV spectra of irradiated with various type radiation samples suggests that generated free radicals are not influenced by the nature of radiation. The lack of difference in the line width of the separate lines or the whole EPR spectrum, obtained for gamma and heavy particles irradiation, suggests negligible spin–spin interaction among the radiation-generated free radicals in the samples. The linear dependence of the EPR response on the absorbed dose radiation is found to be higher when generated by gamma rays, than by the same absorbed dose of heavy particles. In addition, the EPR response for carbon ions is higher than that for nitrogen ions. Water solutions of irradiated sucrose exhibit UV spectrum with absorption maximum at 267 nm, attributed to the recombination products of free radicals. The UV band intensity depends on the absorbed dose radiation. The UV spectra obtained for carbon, nitrogen and gamma rays irradiated sucrose are also compared.     

EPR and UV spectroscopic investigations of sucrose irradiated with heavy-ion particles

Crystalline sucrose irradiated with C and Si ions is investigated with EPR and UV spectroscopy. Samples are treated at different doses of radiation in the region 20–300 Gy and linear energy transfer (LET) values of 39.6, 49 and 58 keV μm^?1 for C ions and 60 keV μm^?1 for Si ions. All samples exhibit identical EPR spectra due to radiation-induced stable sucrose radicals. At given constant LET the EPR signal responses are linear to the absorbed doses of Si and C ions. Water solutions of irradiated sucrose exhibit UV absorption maximum at 267 nm due to the product of radical recombination. The intensity of this band is stronger at irradiation with Si than with C ions. UV absorption is more sensitive to heavy-ion species irradiation than the EPR signals.     

EPR of gamma irradiated solid sucrose and UV spectra of its solution. An attempt for calibration of solid state/EPR dosimetry

A simple new approach for independent calibration of solid state/EPR (SS/EPR) dosimetry system is reported. It is based on the fact that: (i) gamma-irradiation of solid sucrose (sugar) induces stable EPR detectable free radicals accompanied by UV detectable brown colour stable in the solid state and in solution; (ii) both the EPR intensity of gamma-irradiated solid sucrose and its solution UV absorbance linearly depend on the absorbed dose high energy radiation and may be independently used for dosimetric purpose; (iii) UV spectrometers are calibrated. The correlation between EPR response and absorbed dose radiation of solid sucrose and UV absorption of its solutions is used in the present communication for calibration purpose. The procedure of sucrose extraction from sucrose-paraffin dosimeters is described. The calibration procedure may be applied to any other (alanine, self-calibrated, etc.) SS/EPR dosimeters, simultaneously irradiated with sucrose.     

XRD and EPR structural investigation of some zinc borate glasses doped with iron ions

Glasses in the system xFe₂O₃·(100?x) [45ZnO·55B₂O₃] (0≤x≤10 mol%) have been prepared by melting at 1200 °C and rapidly cooling at room temperature. The obtained samples were submitted to an additional thermal treatment at 570 °C for 12 h in order to relax the glass structure as well as to improve the local order. The as cast and heat treated samples were investigated using X-ray diffraction (XRD) and electron paramagnetic resonance (EPR) measurements. The XRD patterns of all the studied samples show their vitreous nature. Structural modifications occurring in the heat treated samples compared to the untreated ones have been pointed out. EPR spectra of untreated and heat treated samples revealed resonance absorptions centered at g≈2.0, g≈4.3 and g≈6.4. The compositional variation of the line intensity and linewidth of the absorptions from g≈4.3 and g≈2.0 have been interpreted in terms of the variation in the concentration of the Fe³⁺ ions and the interaction between the iron ions. The EPR spectra of the untreated samples containing 5 mol% Fe₂O₃ have been studied at different temperatures (110–290 K). The line intensity of the resonance signals decreases with increase in temperature whereas the linewidth is found to be independent of temperature. It was also found that the temperature variation of reciprocal line intensity obeys the Boltzmann law.     

The variation of defect damage with depth in molybdenum irradiated with 2MeV nitrogen ions

Transmission electron microscopy has been used to examine the damage produced in specimens of high purity molybdenum following irradiation with 2 MeV nitrogen ions in the Van de Graaff accelerator. A simple electropolishing technique was developed to allow the defect damage to be examined at different depths on a single specimen. Some results are presented here for specimens irradiated in the range 600–800°C, together with theoretical predictions of the nitrogen range and the variation of displacement damage with range, The experimental results show that the defect damage to the lattice results in a structure of dislocation loops, interstitial in nature, whose size drops with distance from the bombarded surface and whose concentration increases. Nevertheless the retained defect damage, measured by integrated loop area, agrees reasonably with the theoretical variation of displacement damage with range while the increase in loop concentration with depth coincides with the variation in ratio of nitrogen concentration to displacement damage. This latter result agrees with the hypothesis that the nucleation of damage is controlled to a large extent by the ratio of impurity atoms to displaced atoms.     

FT-IR spectroscopy of carbon dioxide in CR-39 and SR-90 track detectors irradiated with ions and gamma-rays at different energies and fluences

Two types of polymeric track detectors CR-39 and SR-90 were irradiated with protons, alpha particles, heavy ions and gamma-rays at different energies and fluences. After irradiation these detectors were analyzed with an FT-IR spectrometer of Jasco type 5300 in transmission and ATR modes. We have found that CO₂ is produced not only by irradiation but also by polymerization. The amount of CO₂ in the detector material is closely related to the latent track formation.     

Identification of irradiated crab using EPR

EPR spectroscopy is a fast and powerful technique for the identification of irradiated food. Crab exoskeleton was divided into six parts: dactyl, cheliped, carapace, apron, swimming legs, and walking legs. Samples of the exoskeleton were prepared and irradiated to Cs-137 gamma radiation in the range (1.156–5.365 kGy). EPR spectra of unirradiated as well as irradiated samples were recorded and analyzed. Response to gamma radiation was plotted for each part of the exoskeleton, dactyl was found to be the most sensitive part, followed by the apron (38%), cheliped (37%), walking legs (30%), swimming legs (24%), and carapace (21%) relative to the dactyl response.     

EPR investigation of the accumulation of F+ centers in irradiated MgO:Mn crystals

According to electron paramagnetic resonance spectra of MgO:Mn crystals irradiated in a reactor, the dependences of the concentration of F⁺ centers on the irradiation dose and on the content of impurities have been obtained. The strong influence of paramagnetic Mn²⁺ ions on the efficiency of the accumulation of F⁺ centers is determined.     

EPR investigations of bonding and activation of nitrogen oxides by surface complexes of transition metal ions

EPR spectroscopy has been used to investigate changes occurring at the molecular level during coordination and activation of NO and N₂O small pollutant molecules on Cu/ZSM-5 and Mo/SiO₂ catalysts, respectively. It is shown that the activation of nitric oxide occurs by formation of a bent η¹{CuNO}¹¹ surface adduct with rehybridization of the NO Orbitals. The spin Hamiltonian parameters of this species have been analyzed in detail, leading to a molecular and electronic picture of the complex. The mechanism along which N₂O is decomposed upon interaction with surface Mo⁵⁺ species involves dissociative metal-to-ligand electron transfer. The reaction was monitored by EPR using naturally abundant and⁹⁵Mo-enriched molybdenum. The dynamics of the N-O bond cleavage is discussed in terms of two-dimensional Morse potential energy surfaces. From the EPR parameters of the resultant O⁻ radical, the spin density distribution and the stabilization energy were calculated.     

Transformations of radicals and ions in irradiated sodium sulfate doped with nitrate ions

The structure and properties of the paramagnetic centers formed by γ-irradiation at 77 K in sodium sulfate doped with nitrate ions have been investigated by the EPR method. The NO^2? ₃, NO₂ and SO^? ₄ radicals have been identified. The orientation of NO^2? ₃ relation to crystallographic axes is determined. In the 77-400 K temperature range the transformations of observable radicals have been studied. The mechanisms of their formation and thermal annealing have been discussed. The symmetry of nitrate ions in sodium sulfate was investigated by diffuse reflectance infrared Fourier transform spectroscopy. At the concentration of NO^? ₃ up to 5.5 × 10¹⁸ g^?1 the nitrate ion was supposed to have a planar or pyramidal configuration of the D_3h or C_3V symmetries. At the concentration of the dopant higher than 5.5 × 10¹⁸ g^?1 the nitrate ions with the C_2V symmetry were observed.     

EPR of ultraviolet irradiated lithium hydride crystals

Results are presented of EPR measurements on lithium hydride single crystals at low temperatures. Loose aggregates of F-centers are formed during u.v. irradiation. The F-center production is interpreted as an excitonic process where the interstitials are stabilized as H₂-molecules.     

EPR study of neutron irradiated Ge-S glasses

The results of EPR measurements on neutron irradiated Ge-S glasses doped by Mn are presented. It has been found that the integrated neutron flux from 1·1 × 10¹⁵ n. cm^–2 to 1·5× × 10¹⁷n. cm^–2 has no detectable effect on the nearest neighbour surroundings of Mn²⁺ probing ions but increases the intensity of all EPR lines. A new EPR line was detected in Mn-doped Ge-S glasses irradiated with the highest neutron dose of 1·5 × 10¹⁷ n. cm^–2.     

EPR studies of the X-ray irradiated dithiophosphate salts

The powder EPR spectra of some ammonium and potassium salts of dithiophosphoric acid, (RO)₂P(S)SH, irradiated with X-rays at 77 K have been recorded and analyzed in respect to their distinguishable EPR-active components. In general each EPR spectrum is a superposition of isotropic and anisotropic features from a number of carbon- and phosphorus-centered radicals. Whereas carbon-centered radicals are practically isotropic the phosphorus-centered species exhibit threefold anisotropy with a large (700–800 G) isotropic³¹P hyperfine splitting. The identification of the latter is based on the magnitudes of the³¹P splitting as well as on the phosphorous 3p/3s spin densities ratio. The experimentally obtained EPR parameters of the studied radicals are refined using computer simulation procedure.     

Blistering of rhenium irradiated with 21keV helium ions

This paper describes blistering of rhenium following 21 keV He⁺-ion irradiation at temperatures between 300 K and 1200 K. Blistering starts at 300 K at a dose of 3×10¹⁷ ions/cm². The most probable blister diameter varies from 4400 ? at 300 K to 10100 ? at 1200 K. The blister depth τ _bl , the blister diameter φ _bl and the blister heighth _bi show a distribution. From the observations one could derive the following relationships:h _bl = 0.35φ _bl ; τ _bl =3.43φ _bl ^2/3 . The erosion yieldE _y due to blistering is function of doseE _y =0.51 atoms/ion at 3×10¹⁷ ions/cm²,E _y =0.56 atoms/ion at 6×10¹⁷ ions/cm² andE _y =0.14 atoms/ion at 3×10¹⁸ ions/cm². The sputtering yieldS (21 keV) is estimated to be ∼0.1 atom/ion. The corresponding surface regression is 44? at 3×10¹⁷ ions/cm² and 1323 ? at 9×10¹⁸ ions/cm². Surface regression has therefore little influence on the observations at low doses. Work performed at the Mathematicals Science Department of S.C.K./C.E.N. at Mol (Belgium)     

EPR studies of X-ray irradiated dithiophosphate metal complexes

Different metal O,O’-disubstituted dithiophosphates have been studied by Electron Paramagnetic Resonance (EPR) spectroscopy after X-ray irradiation at 77K. Formation of different radicals has been recorded depending on the central metal atom and on the substituents in the ligands. Phosphorus-centered radicals with hyperfine constants of about 800 G were recorded after radiolysis of zinc and cadmium complexes. Their shape and EPR parameters lead to their identification as phosphoranyl radicals (RO)₂P (S)S^?. In these compounds two different types of coordination of the ligands have been found by X-ray analysis. One dithiophosphate group is coordinated to the metal atom forming a chelate four-membered ring, and another one is a bridging group. The formation of phosphorus-centered radicals is related to the presence of a bridging, or interchelating group. In other metal dithiophosphates, with only chelating groups present, such radicals were not found. In platinum, palladium and nickel dithiophosphates similar EPR signals with small hyperfine coupling were observed. They have been identified as carbon-centered radicals with one phosphorus in γ-position.     

EPR investigations of mesoporous silica doped with metal transitions ions

Electron paramagnetic resonance (EPR) experiments were performed on mesoporous silica powders in which (1,4,8,11-tetraazacyclotetradecane) cyclam groups were incorporated. These functionalised groups allow an easy binding with copper and nickel ions. Comparative studies are carried out on samples functionalised by cyclam groups located either inside the pores or in the walls of the mesoporous structures. Copper and nickel EPR parameters, including g-tensors and hyperfine components are determined and relevant electronic, magnetic and structural information are obtained. The EPR spectra intensities and line-widths are investigated on the temperature range [4 K,300 K] to clarify the relative dispersion or agglomeration of the doping ions in the matrices as well as their possible thermally activated mobility and ions pairing. As a support of the experimental EPR investigations, numerical simulations of the geometry of metallic ion environments and their electronic properties are carried out and discussed. The possibility of dynamic Jahn Teller (JT) effect in the temperature range [200, 60 K] is discussed for the nickel doped matrices where the low temperature quenched JT configuration is thought to favour the formation of Ni³⁺ pairs.     

EPR and UV studies of VO ions in potassium d-gluconate monohydrate single crystals

Electron paramagnetic resonance (EPR) of VO²⁺ doped potassium hydrogen d-gluconate single crystals and powder have been examined at room temperature. Single crystal rotations in each of the three mutually orthogonal crystalline planes namely ac, ba and ca indicate two different VO²⁺ complexes. Each complex is located in different chemical environments, each environment containing two magnetically inequivalent VO²⁺ sites in distinct orientations occupying substitutional positions in the lattice and showing a very large angular dependence. The powder spectrum also clearly indicates four different VO²⁺ complexes, confirming the single crystal analysis. Crystalline field around the VO²⁺ ion is nearly axial. The optical absorption spectrum of VO²⁺ ions in the crystal lattice is also studied at room temperature. The characteristic spectrum of the VO²⁺ ions has two absorption bonds. The bond positions are at 17 857 and 11 235 cm^-1. Spin Hamiltonian parameters and molecular orbital coefficients are calculated from the EPR and the optical data, and results are discussed.     

Sensitivity of whole human teeth to fast neutrons and gamma-rays estimated by L-band EPR spectroscopy

This paper reports the first attempt to use L-band spectroscopy for estimating the sensitivity of whole teeth to fast neutrons and gamma-rays. Three teeth were successively irradiated first with fast neutrons with a wide energy spectrum (mean energy around 30 MeV) up to 160 Gy and then with gamma-rays up to 14 Gy. After each irradiation, L-band (1 GHz) EPR spectra of each whole tooth surrounded by the surface–coil resonator were recorded, yielding a single composite line principally due to CO₂⁻ and native radicals. The sensitivities are estimated by the slopes of the linear dose response curves of the dosimetric CO₂⁻ radicals. The ratios of the gamma/neutron sensitivities were found to be in the range 8–9 (±2) for the three teeth.     

Aspects of detection of irradiated foods by EPR spectroscopy

Some methodological aspects important for the detection of irradiated foods by the EPR spectroscopy are discussed. These are: specificity and stability of the EPR signals produced by ionizing radiation in foods, complexity of radiation induced EPR signals and their detection at different doses, the dose dependence of the intensities of the EPR signals involved. The importance of the native EPR signals observed in foods for the detection of irradiation and the role of quantitative measurements in the development of detection methods are shown.     

Post-annealing effects on EPR response of irradiated nano-structure hydroxyapatite

In this work, the nano-structure hydroxyapatite was synthesized via the hydrolysis method. The produced powders were thermally treatment at different temperatures from 400 to 1200°C. The morphological and chemical analyses were carried out using the Fourier transmission infrared spectroscopy, transmission electron microscopy, and X-ray diffraction system. Then, the samples were irradiated at different absorbed doses from 1 to 80 kGy using ⁶⁰Co γ -ray. Electron paramagnetic resonance (EPR) responses of the samples were measured at room temperature in air. Subsequently, the variations of EPR signal intensities were constructed as the peak-to-peak signal amplitude and results were compared with those of non-annealed samples. The results show that the EPR responses of non-annealed samples are higher rather than other samples and also are saturated at higher doses in comparison with the others.