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 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.     

Comparative investigations of TL and OSL in KCI:Eu2+ crystals irradiated with UV and X-rays

Abstract

We present thermoluminescence (TL) glow curves and optical stimulated luminescence (OSL) response from both KCl:Eu²⁺ crystals irradiated with soft X-rays (20 KV, 80 μA) and ultraviolet light (230 nm). Two situations take place. First, we observed that for long time F-light bleaching (560 nm) the typical TL glow curve of X-rays irradiated KCl:Eu²⁺ resembles the TL glow curve of UV-irradiated samples. Second, along with OSL measurements, we have performed a thermal bleaching and we have addressed F and F_z participation in OSL. These results provide us a supportable correlation between F and F_z as responsible centers for OSL and TL processes.     

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.     

Infrared spectroscopic investigations of bauxites

Journal of Applied Spectroscopy -     

Terahertz spectroscopic investigations of explosives

Experimental measurement and theoretical analysis of THz spectrum for five different explosives and related compounds are introduced. The refractive index and absorption coefficient of the samples are measured in the region of 0.2–2.6 terahertz by time-domain spectroscopy. The simulated spectrum of γ-HNIW is in agreement with the experimental data.     

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.     

Influence of neutron and heavy-ion irradiation on EPR spectra of CuGeO3

The influence of neutron and heavy-ion irradiation on the electron paramagnetic resonance (EPR) spectra of the spin-Peierls compound CuGeO₃ has been investigated in the wide temperature range of 2–300 K. It is found that the neutron irradiation leads to a decrease of the spin-Peierls transition temperature and induces appreciable changes in the EPR signal intensity, resonance line width andg-factor of this material. These changes may be associated with a partial suppression of both the energy gap and dimerization within the Cu chains due to the irradiation-induced changes in the topological and chemical short-range order. In contrast to this, the heavy-ion irradiation induces only an increase in the intensity of the EPR signal and does not produce appreciable changes in the resonance line width,g-factor and spin-Peierls transition temperature. The experimental results show a large increase in the Curie-Weiss component and complete suppression of the spin-Peierls transition for higher irradiation doses.     

EPR investigations of SiC and SiOC nanometric powders

EPR investigations are performed in SiC and SiOC nanometric powders annealed between 1200 and 1800°C. By using different EPR frequency bands and a suitable spectra analysis, three quite different paramagnetic defects with well defined $\tilde g_i $ (i=1, 2, 3) and hyperfine $\tilde A_i $ (i=1, 2) tensors account for the EPR signal in these materials. The defects are characterized by $\tilde g_1 $ (g ₁ ^‖ =2.0046(3), g ₁ ^? =2.0023(3)), $\tilde g_2 $ (g ₂ ^‖ =2.0037(3), g ₂ ^? =2.0028(3)) and isotropic $\tilde g_3 $ (2.0030(3)) tensors. In SiC powders, the defects assignment is discussed with respect to the different SiC forms, namely α-SiC and β-SiC polytypes as well as amorphous SiC and carbon present in minor concentration in the network. In SiOC powders, the above defects are evidenced only at high annealing temperature (T _a≥1200°C) when the oxygen contained is highly reduced.     

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.     

Azimuthal structures of produced particles in heavy-ion interactions

The angular structures of particles produced in ²⁰⁸Pb at 158 A GeV/c and ¹⁹⁷Au at 11.6 A GeV/c induced interactions with Ag(Br) nuclei in emulsion detector have been investigated. Nonstatistical well-ordered ring-like structures of produced particles in azimuthal plane of a collision have been found, and their parameters have been determined. The text was submitted by the authors in English.     

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 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.     

EPR and ENDOR investigations of Sn impurities in CdS

Wurtzite type CdS single crystals with tin impurities have been reinvestigated by means of magnetic resonance. The by far strongest neighbour interaction with the rare isotope³³S is detectable by electron paramagnetic resonance (EPR), while nine weaker cadmium interactions can be resolved with the electron nuclear double resonance (ENDOR) technique. Three distinct shell symmetries are detected and can be explained by the wurtzite lattice symmetry. The parameters evaluated are interpreted in terms of the LCAO approach. An additional Sn-related spectrum, being not resolvable by ordinary EPR was identified by means of ENDOR-induced-EPR (EI-EPR) and turned out to be associated with Lithium.     

ESR investigations of electron-beam irradiated cellulose nitrate

Electron spin resonance investigations on an electron-beam irradiated solid state nuclear track detector, based on cellulose nitrate (KODAK LR-311), are reported. The nature of free radicals induced in polymers by irradiation is discussed. The dependence of resonance spectral parameters on irradiation times, as well as on storage time and temperature, is studied. The experimental results are related to the stability of latent tracks and it is concluded that the free radicals induced by irradiation are located within the latent tracks. We have shown that both latent track and free radical thermal fading obey an Arrheniuslike dependence, with the same activation energy.     

EPR spectroscopic and X-Ray diffraction studies of carbon fibers with different mechanical properties

The carbon fibers obtained by carbonization of polyacrylonitrile fibers were studied by electron paramagnetic resonance and X-ray diffraction analysis in the range of small and wide scattering angles. Their elastic and strength characteristics were also studied. The concentration of the paramagnetic centers was correlated with the mechanical properties of carbon fibers. The wide-angle X-ray diffraction study did not reveal essential structural differences in the carbon fiber samples with different mechanical properties. At the same time, the small-angle X-ray scattering study showed that the fiber nanostructures with different mechanical properties differ substantially.