Neutron bound beta-decay: BOB

Frozen solution samples were made from gold chloride and KAu(CN)₂ solvated with TBP/xylene. The ¹⁹⁷Au M?ssbauer parameters were similar to those same species as frozen solutions or adsorbed onto activated carbon. Solvated samples from EuO dissolved in HCl or H₂SO₄ and frozen gave characteristic Eu(III) spectra. All the spectra were consistent with bonding to the TBP being through hydronium ions or water molecules.     

Structure of complexes in the H<Subscript>2</Subscript>SO<Subscript>4</Subscript>—2-pyrrolidone system as determined by IR-spectroscopy and quantum-chemical calculations

Specific features of complexation in solutions of a strong dibasic acid in the H₂SO₄–2-pyrrolidone (Pyr) system (in the range of compositions of 0–100% H₂SO₄) are studied using multiple frustrated total internal reflection IR spectroscopy. The conclusions drawn on the structure of the complexes formed in such solutions are confirmed by quantum-chemical calculations of the mPyr · nH₂SO₄ (m, n = 1, 2) heteroassociates and by comparison of their calculated and measured vibrational spectra. It is found that, in the investigated solutions, four types of acid–base complexes, with various degrees of proton transfer in the OHO bridge, are formed: (AHA)^– anions with quasi-symmetric H-bonds, solvated by acid molecules, or entering into the composition of PyrH⁺ · (AHA)^– ion pairs; quasi-ion pairs with incomplete proton transfer to the base molecule of 1: 1 and 2: 2 compositions; and 2Pyr · H₂SO₄ complexes with two O–H···O bridges of molecular type. The main differences in the mechanisms of the acid–base interactions in the H₂SO₄–Pyr system as compared to the CH₃SO₃H–Pyr system result from the participation of two OH-groups of H₂SO₄ molecule in these interactions. Therefore, two types of quasi-ion pairs and complexes of 2Pyr · H₂SO₄ composition are formed.     

Inhibition of iron corrosion in 0.5 M sulphuric acid by metal cations

Corrosion inhibitors are widely used in acid solutions during pickling and descaling. Mostly organic compounds containing N, O, and S groups are employed as inhibitors. In this study, the inhibition performance of metal cations such as Zn²⁺, Mn²⁺ and Ce⁴⁺ ions in the concentration range 1-10 × 10⁻³ M has been found out. The corrosion behaviour of iron in 0.5 M H₂SO₄ in the presence of metal cations is studied using polarization and impedance methods. It is found that the addition of these metal cations inhibits the corrosion markedly. The inhibition effect is in the following order Ce⁴⁺ ? Mn²⁺ > Zn²⁺.     

Ratiometric detection of Raman hydration shell spectra

The micro‐structure of hydration shell of solute in water is significant for understanding the properties of aqueous solutions. However the spectra of hydration shell are difficult to be obtained. Herein, a novel Raman ratio spectra, which is obtained through dividing the Raman spectra of aqueous solutions from the spectrum of water, was applied to deduce the spectra of hydration shell of organic (acetone‐D6) and inorganic compounds (NaNO₃, NaSCN, NaClO₄, Na₂SO₄, NaCl) in water. Those spectra of the hydration shell were employed to study the micro‐structures of the first hydration shells of anions, the number of water molecules in the first hydration shell of free anions and acetone‐D6, and the aggregation behavior of ions in the concentrated aqueous NaNO₃. The number of water molecules in the hydration shell was supported by our molecular dynamic simulations. The Raman ratio spectra can be widely employed to obtain the spectra of the first hydration shell, and it is helpful to understand the micro‐structure of aqueous solutions. Copyright © 2016 John Wiley & Sons, Ltd.     

The Application of Raman Spectroscopy to the Study of the Uranyl Mineral Coconinoite Fe2Al2(UO2)2(PO4)4(SO4)(OH)2 · 20H2O

ABSTRACT

Raman spectra of the uranyl-containing mineral coconinoite, Fe₂Al₂(UO₂)₂(PO₄)₄(SO₄)(OH)₂ · 20H₂O, are presented and compared with the mineral's infrared spectra. Bands connected with (UO₂)²⁺, (PO₄)^3?, (SO₄)^2?, (OH)^?, and H₂O stretching and bending vibrations are assigned. Approximate U?O bond lengths in uranyl, (UO₂)²⁺, and O?H…O hydrogen bond lengths are calculated from the wavenumbers of the U?O stretching vibrations and (OH)^? and H₂O stretching vibrations, respectively, and compared with published data for similar natural and synthetic compounds.     

Calculation of hydrogen generation from plutonium-induced alpha radiolysis of nitric,sulfuric, and perchloric acids

Abstract

Uranylion was reduced to U⁴⁺ by ionizing radiation in deoxygenated solutions containing organic solutes. This reduction is effected by free radical species formed from the organics and perhaps in part by H atoms from H₂O decomposition. A detailed study of uranyl oxalate solutions showed that the role of H₂O₂ in this system is complex and that chain-type reactions involving this species can occur.     

Raman study of cation effect on sulfate vibration modes in solid state and in aqueous solutions

Raman spectra of potassium, sodium, and ammonium sulfates (K₂SO₄, Na₂SO₄, and (NH₄)₂SO₄) are reported and analyzed. These sulfates have been investigated under two states: solid (anhydrous and hydrated) salts and aqueous solutions. The effects of monovalent ions (K⁺, Na⁺, and NH₄⁺) and hydration on the position of Raman lines assigned to internal vibrations of sulfate anion SO₄²⁻ are discussed. In solid salts, the line position of each Raman peak is shown to decrease with increasing radius of the cation. The main ν₁ mode of sulfate molecule is particularly affected. It is emphasized that this sensitivity in solid sulfates vanishes in aqueous solutions. As a consequence, this mode can be probed by Raman spectroscopy as the main signature of SO₄²⁻ to determine its concentration within a single calibration. Copyright © 2013 John Wiley & Sons, Ltd.     

Thermoluminescence and ESR phenomena in X-ray irradiated mixed alkaline-alkaline earth metal sulfates—I

Abstract

Thermoluminescence (TL) and ESR phenomena induced by X-ray irradiation of the mixed samples of K₂SO₄ and alkaline earth metal sulfate (MgSO₄ or BaSO₄) were investigated in terms of the reactivities and the crystallogrpahic properties. A high intensive TL resulted from the diffusion of a small amount of Mg²⁺ into K₂SO₄ crystals. The amount formed of K₂Mg₂(SO₄)₃, langbeinite, compound had a maximum at the stoichiometric composition. From the ESR measurements, SO^? ₃ radicals were found to be easily formed in the langebeinite by excitation. Both the TL and the ESR phenomena were hardly observed in the K₂SO₄–BaSO₄ system due to little diffusion of Ba²⁺ with much larger radius than Mg²⁺. The results were mainly discussed on the basis of the radii of the component cations in these systems. In addition, the fundamental data as to the application to the ESR dosimetry were obtained.     

Mechanism of thermoluminescence in Sm- and Eu-doped barium sulphate

Thermoluminescence, TL emission spectra, ESR and optically excited luminescence of BaSO₄:Sm and BaSO₄:Eu were investigated. The optically excited luminescence studies showed that samarium ions were stabilized in the trivalent state in doped samples, and a fraction of these ions was reduced to the divalent state on γ-irradiation. These reduced ions were reoxidized on thermal annealing. Europium was found to be stabilized in the divalent form in BaSO₄:Eu phosphor, both before and after γ-irradiation. These results were further confirmed from the emission spectra of different glow peaks from BaSO₄:Sm and BaSO₄:Eu samples. The ESR spectra of these samples, recorded after γ-irradiation and various post-irradiation thermal annealings, revealed that anion radicals (such as SO₄^?, SO₃^?, SO₂⁺ and O₃^?) are formed on γ-irradiation and get annihilated at temperatures which corresponds to some of the glow peaks. An attempt is made to explain the results by a mechanism, suggested earlier for other impurity-doped BaSO₄ phosphors, in which holes released on thermal activation from anion radicals recombine with the electrons trapped at certain defect centres and the energy thus released is non-radiatively transferred to the impurity ions, which give their characteristic emission.     

Influence of N‐Substitution on Electron Spin Resonance (ESR) Behavior of 2‐(2‐Nitrophenyl)‐1H‐benzimidazole Derivatives

Abstract

The synthesis of 2‐(2‐nitrophenyl)‐1H‐benzimidazole (1), 1‐benzoyl‐2‐(2‐nitrophenyl)‐1H ‐benzimidazole (2), and 1‐acetyl‐2‐(2‐nitrophenyl)‐1H‐benzimidazole (3) is reported. Stable radical anions (1 ^·?, 2 ^·?, and 3 ^·?) were generated by chemical reduction in DMSO and studied by ESR spectroscopy. The interpretation of the ESR spectra was done by means of computational simulation process. Hyperfine coupling constants were assigned by comparison with related compounds, and on the basis of calculation based on SCF INDO MO method in the unrestricted Hartree–Fock scheme.     

ESR studies on calcite encrustation on Fili neotectonic fault, Greece

Electron spin resonance (ESR) study was done on calcite encrustation on Fili neotectonic fault surface, Greece. Normally such calcite encrustations on fault surfaces are not observed. Significantly, the ESR study has detected the presence of nitrate NO₃²⁻ radical in this calcite encrustation, havingg _⊥=2.0063±0.0001 and hyperfine coupling constantA _⊥=3.44 mT, the second such detection of nitrate NO₃²⁻ radical following a sample from Scott Glacier, Antarctica. From isochronal thermal annealing measurement the NO₃²⁻ radical was found to be quite stable, only fully annealed at 475°C. This study also shows that the ESR, as a tool, can be suitably applied to date the age of formation of the calcite encrustation with SO₃⁻ as an ESR dating signal by additive γ-ray irradiation. A preliminary estimation indicates the age of formation of calcite precipitation at Fili fault, Greece to be about 5600 years.     

Concentration Fluorescence Quenching of L(-)-Tyrosine in Aqueous and Nonaqueous Solutions

Abstract

A number of studies have demonstrated the dependence of both the fluorescence lifetimes and quantum yields of tyrosine in solution upon the nature of the solvent as well as upon the absence or the presence of air in the tyrosine solutions employed. Photobleaching of tyrosine in vacuum at pH 6.1 was found to be practically zero, whereas exposure of tyrosine to the full light of a Hglamp for 10 to 20 minutes gave rise to formation of non-fluorescing photoproducts⁽¹⁾. In addition, the phosphorescence lifetimes of tyrosine were determined as 2.7⁺?0.2 sect 2.7⁺0.2 sec. and < 1 sec in 1% ETOH in aqueous solution and at pH 6.1 and pH 13, respectively(l). The very long phosphorescence lifetimes are definitely responsible to a considerable extent as far as photobleaching is concerned. However, the participation of the excited singlet state cannot be ruled out. In a review, the fluorescence lifetimes of tyrosine in queous solutions were found to vary between 2.6 nsec to 3.6 nsec⁽²⁾. On the other hand, the fluorescence quantum yields of tyrosine and various anologous compounds displayed a strong dependence upon the solvent. Such solvents used were water, n-butanol and p-dioxane. The following values of φ_fl were obtained: For p-HO-C₆H₄ -CH₂COOH; φ_fl=0.01, 0.22 and 0.34; for p-HO-C₆H₄-CH₃; φ_fl= 0.23, 0.39 and 0.45 and for p-HO-C₆H₄-CH₂CN; φ_fl =0.16, 0.34 and 0.34, respectively⁽³⁾. Furthermore, the value φ_fl of p-HO-C₆H₄-CH₂CH(NH⁺ ₃)C00^? in aqueous solutions was found to be 0.21, where- as that of p-HO-C₆H₄-CH²CH(NH⁺ ₃)COOH in similar solutions was 0.06. The fluorescence lifetime and quantum yield of phenol in Ethanol were found to be 4.7 nsec and 0.10, respectively⁽⁴⁾.     

The structural transformation of monoclinic [(R)-C5H14N2][Cu(SO4)2(H2O)4]·2H2O into orthorhombic [(R)-C5H14N2]2[Cu(H2O)6](SO4)3: crystal structures and thermal behavior

Single crystals of [(R)-C₅H₁₄N₂][Cu(SO₄)₂(H₂O)₄]·2H₂O (1) were grown through the slow evaporation of a solution containing H₂SO₄, (R)-C₅H₁₂N₂ and CuSO₄·5H₂O. These crystals spontaneously transform to [(R)-C₅H₁₄N₂]₂[Cu(H₂O)₆](SO₄)₃ (2) over the course of four days at room temperature. The same single crystal on the same mounting was used for the determination of the structure of (1) and the unit cell determination of (2). A second single crystal of the transformed batch has served for the structural determination of (2). Compound 1 crystallizes in the noncentrosymmetric space group P2₁ (No. 4) and consists of trimeric [Cu(SO₄)₂(H₂O)₄]^2? anions, [(R)-C₅H₁₄N₂]²⁺ cations and occluded water molecules. Compound 2 crystallizes in P2₁2₁2 (No. 18) and contains [Cu(H₂O)₆]²⁺ cations, [SO₄]^2? anions and occluded water molecules. The thermal decompositions of compounds 1 and 2 were studied by thermogravimetric analyses and temperature-dependent X-ray diffraction.     

Molar extinction coefficients of solutions of some organic compounds

Molar extinction coefficients of aqueous solutions of some organic compounds, viz. formamide (CH₃NO),N-methylformamide (C₂H₅NO),NN-dimethylformamide (C₃H₇NO),NN-dimethylacetamide (C₄H₉NO), 1,4-dioxane (C₄H₈O₂₄), succinimide (C₄H₅NO₂) and solutions of acetamide (C₂H₅NO) and benzoic acid (C₇H₆O₂) in 1,4-dioxane (C₄H₈O₂) have been determined by narrow beam γ-ray transmission method at 81, 356, 511, 662, 1173 and 1332 keV. The experimental values of mass attenuation coefficients of these compounds have been used to calculate effective atomic numbers and electron densities. The additivity rule earlier used for aqueous solution has been extended to non-aqueous (1,4-dioxane) solutions.     

Hydrogen-assisted fabrication of spherical gold nanoparticles through sonochemical reduction of tetrachloride gold(III) ions in water

Spherical gold nanoparticles (AuNPs) were selectively synthesized through sonochemical reduction of tetrachloride gold(III) ions ([AuCl₄]⁻) in an aqueous solution of hydrogen tetrachloroaurate(III) tetrahydrate (HAuCl₄·4H₂O) with the aid of hydrogen (H₂) gas in the absence of any additional capping agents. On the other hand, various shaped-AuNPs such as spherical nanoparticles, triangular and hexagonal plates were formed from sonochemical reduction of [AuCl₄]⁻ in argon (Ar)-, nitrogen (N₂)- or oxygen (O₂)-purged aqueous [AuCl₄]⁻ solutions. The selective fabrication of spherical AuNPs assisted by H₂ gas is most likely attributed to the generation of hydrogen radicals (H) promoted by the reaction of H₂ introduced and hydrogen oxide radicals (OH) produced by sonolysis of water.     

Electron paramagnetic resonance of NH 3 + radical in potassium sulphate

Room temperature EPR spectra of (NH₄)₂SO₄ doped K₂SO₄ monocrystals irradiated with x-rays show the presence of NH₃ ⁺ radicals. The EPR parameters areg ‖=2.0037 andg ⊥ = 2.0068;¹⁴NA _XX=13.75;A _YY=24.5;A _ZZ=25.5 gauss;¹HA _XX=A _YY=22 andA _ZZ=25 gauss. From the¹⁴N and¹H coupling constants it has been inferred that at room temperature the planar NH₃ ⁺ radical undergoes rotation about theC ₃ axis which corroborates with the equivalence of the protons, but the radical itself is in an asymmetric crystal field environment. The 77K spectra indicate a considerable reduction in the motion of the radical with the free motion almost completely stopped. Part of Ph.D. work of the second author     

Surface characterisation of ethylene-propylene-diene rubber upon exposure to aqueous acidic solution

Two types of pure ethylene propylene diene rubbers were exposed to two different acids for varying period of time. Surface characterisation was carried out using X-ray photoelectron spectroscopy (XPS). Two EPDM rubbers selected for this study were comparable in co-monomer compositions but significantly different with respect to molar mass and the presence of long chain branching. Both rubbers contained 5-ethylidene-2-norbornene (ENB) as diene. Solution cast films of pure EPDM samples were exposed in two different acidic solutions, viz. chromosulphuric (Cr (VI)/H₂SO₄) and sulphuric acid (H₂SO₄) (20%, v/v) at ambient temperature from 1 to 12 weeks. XPS analysis indicated that several oxygenated species were formed on the surface of both rubbers after exposure. It was postulated from the XPS analyses that both aqueous acidic solutions attacked the olefinic double bonds (CC) of ENB. Furthermore, 20% Cr (VI)/H₂SO₄ also attacked the allylic carbon-hydrogen (CH) bonds of ENB resulting in more oxygenated species on the surface compared to 20% H₂SO₄ under identical conditions. Cr (VI) in the 20% Cr (VI)/H₂SO₄ was found to play an important role in alteration of surface chemistry. Studies using a model system consisting of EPDM mixed with Cr (VI) and Cr (III) salts revealed that the change of oxidation state from Cr (VI) to Cr (III) as a consequence of direct involvement of Cr (VI) in the chemical alteration of EPDM surfaces. Interestingly, the presence of long chain branching and molar mass did not significantly influence the chemical processes owing to the acid treatment.     

ESR response of gamma-irradiated sulfamethazine

In the present work, characteristic features of the radiolytical intermediates produced in gamma-irradiated solid sulfamethazine (SMH) were investigated by electron spin resonance (ESR) spectroscopy. The heights of the resonance peaks, measured with respect to the spectrum baseline, were used to monitor microwave saturation, temperature and time-dependent kinetic features of the radical species contributing to the formation of recorded experimental ESR spectra. Three species having different spectroscopic and kinetic features were observed to be produced in gamma-irradiated SMH. SO₂, which is the most sensitive group of radiation in the SMH molecule, was found to be at the origin of radiation-produced ionic radical species. Based on the experimental results derived from the present study, the applicability of ESR spectroscopy to radiosterilization of SMH was discussed. In the dose range of interest (0.5–10 kGy), the radiation yield of solid SMH was calculated to be very low (G=0.45) compared with those obtained for sulfonamide aqueous solutions (G=3.5–5.1). Based on these findings, it was concluded that SMH and SMH-containing drugs could be safely sterilized by gamma radiation and that ESR spectroscopy could be successfully used as a potential technique for monitoring their radiosterilization.     

Dose quality determined using ESR imaging

The differences in SO⁻₃ radical distribution produced in gadolinium (Gd)-doped glaserite (K₃Na(SO₄)₂) rod after irradiation with β-, γ-, or X-rays was investigated by an electron spin resonance (ESR) imaging method. In β- or X-irradiated samples, the SO⁻₃ radical distribution showed a steep gradient in the rod. In γ-irradiated samples, the distribution showed only a slight gradient in the rod. From these results, ESR imaging can not only detect the radiation direction and the absorbed dose, but can also be expected to distinguish the dose quality.     

Electron Spin Resonance of Free Radicals Produced by Ultraviolet Photolysis in Some Vegetables and Their Juices

Abstract

Paramagnetic species produced by ultraviolet photolysis in various vegetables of domestic origin have been investigated by electron spin resonance technique. The ESR spectra of the small cut pieces of the vegetable fleshes and their frozen juices have been investigated before and under UV photolysis. The samples of potato and carrod exhibit too complex ESR spectra, but parsley, dill, white radish and green pepper do not exhibit any ESR signal before UV photolysis at 113 K. However both the small cut pieces of fleshes of potato, carrot, parsley, dill, white radish and green pepper and their juices exhibit ESR spectra during UV photolysis that we attributed to the H?O and CO^? ₂ radicals. The ESR parameters of these radicals have been obtained and the origins of these radicals have been shown to be the glucose molecules in the carbohydrate chains of these substances.