Initiation of nuclear reactions under laser irradiation of metal nanoparticles in the presence of thorium aqua ions

Laser irradiation of tungsten and gold nanoparticles in aqueous solutions of Th(NO₃)₄ was experimentally studied. Picosecond Nd:YAG lasers with a wavelength of 1.06 μm and a peak power from 10¹¹ to 10¹³ W cm⁻² were used. The composition of colloidal solutions before and after laser irradiation was analyzed using atomic absorption and gamma spectrometry. It was found that laser irradiation initiates nuclear reactions involving thorium nuclei, occurring via two different channels. Radioactive decay of thorium nuclei within its radioactive series is enhanced under laser irradiation in D₂O; one of the fission fragments is ¹³⁷Cs. Possible mechanisms of the process are discussed.     

Atomic beam,optogalvanic and stored ion spectroscopy for radioactive isotopes

Systematic studies of the optical isotope shift and the hyperfine splitting of long chains of stable and radioactive isotopes were performed. The method applied was laser induced resonance absorption; the experimental techniques were the atomic beam method with fluorescence detection and the optogalvanic method. The theory of hyperfine splitting and isotope shift of atoms is reviewed in short with emphasis on the aspects interesting for nuclear physics and on the evaluation problem. The experimental methods are described and their key parameters sensitivity and resolution are discussed. Preliminary results on stored thorium ions are given. Sample results for the nuclear quantity δ<r ²> derived from atomic beam experiments with tin and strontium are presented.     

Increasing the sensitivity of atomic absorption determination of iron

We have studied the effect of the nature and concentration of surfactants on the atomic absorption of iron. We show that using sodium dodecylbenzenesulfonate as the modifier in flame atomic absorption determination of iron in real samples makes it possible to make the measurements in a low-temperature flame (propane-butane-air type) with increased sensitivity and selectivity and also a lower detection limit for iron. We have developed a procedure for atomic absorption determination of iron in food products using sodium dodecylbenzenesulfonate as the modifier. The detection limit for iron is C_min = 0.008 μg/cm³. Report given at the International Congress of Analytical Sciences, ICAS-2006, 20–30 June 2006, Moscow, Russia __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 74, No. 2, pp. 263–266, March–April, 2007.     

Preliminary results of calculations for heavy-water nuclear-power-plant reactors employing <Superscript>235</Superscript>U, <Superscript>233</Superscript>U,and <Superscript>232</Superscript>Th as a fuel and meeting requirements of a nonproliferation of nuclear weapons

A physical design is developed for a gas-cooled heavy-water nuclear reactor intended for a project of a nuclear power plant. As a fuel, the reactor would employ thorium with a small admixture of enriched uranium that contains not more than 20% of ²³⁵U. It operates in the open-cycle mode involving ²³³U production from thorium and its subsequent burnup. The reactor meets the conditions of a nonproliferation of nuclear weapons: the content of fissionable isotopes in uranium at all stages of the process, including the final one, is below the threshold for constructing an atomic bomb, the amount of product plutonium being extremely small.     

Nuclear radii of thorium isotopes from laser spectroscopy of stored ions

Isotope shifts and hyperfine splittings in optical transitions for atomic ions of the thorium isotopes²²⁷Th to²³⁰Th and²³²Th have been measured by laser spectroscopy on stored ions. From the isotope shift data, changes of the mean square charge radii are determined. A continuous increase of the charge radius with mass numberA is observed, in agreement with droplet model calculations. The results indicate that the odd-even staggering for Th is different from that one of the neighbouring isotones of Fr and Ra. There is some empirical evidence from systematics for an inversion of the staggering and the appearance of an octupole deformation atN ≦137. The hyperfine splitting for²²⁹Th for 3 electronic levels is given.     

Comparison of Detection Limits in Atomic Fluorescence and Absorption Spectroscopy

Dagnall, Taylor, and West have recently compared detection limits for a number of metals in atomic fluorescence and absorption spectroscopy and have concluded that “atomic fluorescence measurements using an electrodeless discharge tube are inherently more sensitive than those obtainable by atomic absorption measurements”. Likewise West and Williams have compared the two techniques for magnesium²and silver³, using high-intensity hollow-cathode lamps as sources, and have found much lower detection limits in fluorescence than in absorption.     

钍俘获反应率离线伽马测量方法

为了测定聚变-裂变反应堆模型钍包层中的钍俘获率以及钍-铀转化率, 探索了一种新的钍活化离线γ测量法. 利用测量²³²Th俘获反应产物²³³Th衰变链中²³³Pa衰变放出的311.98 keV 特征γ射线, 来反推计算并最终确定²³²Th(n,γ)²³³Th的反应率, 测试实验中不确定度约6% (²³³Th/²³²Th量级为10^-17情况下). 详细介绍了此方法的背景和原理方法, 并进行简单的校验实验, 证明其能够较好地得到模拟装置中的俘获率. 与瞬发γ测量法以及质谱分析法进行对比, 本方法更适合用于聚变-裂变反应堆模型钍包层中的钍俘获率以及钍-铀转化率测量, 并有望进一步测量其他相关参数.     

Improving Our Knowledge on the 229mThorium Isomer: Toward a Test Bench for Time Variations of Fundamental Constants

For more than four decades, the lowest excitation in the whole landscape of atomic nuclei, the low‐lying, isomeric state of ²²⁹Th, the so‐called thorium isomer, has challenged physicists of various disciplines. Being a solitaire with its uniquely low excitation energy of <10 eV, its predicted lifetime of a few hours results in an extremely sharp relative linewidth ΔE/E as low as 10^–20. While until recently the indication of its existence was based only on indirect evidence, its unique properties inspired a multitude of potential applications, like the use of the thorium isomer as a nuclear frequency standard, potentially able to outperform even the best atomic clocks and a sensitivity‐enhanced access to potential temporal variations of fundamental constants. The various proposals to exploit the unique properties of ^229mTh are presented herein, in particular focusing on its ability to serve as a test bench for time variations of fundamental constants like the fine structure constant.     

14C in uranium and thorium minerals: a signature of cluster radioactivity?

Various uranium and thorium minerals have been analysed with accelerator mass spectrometry to determine their ¹⁴C content. It is found that, whenever the contribution from secondary reactions such as the ¹¹B(α,p)¹⁴C is sufficiently low, the ¹⁴C concentration is consistent with that expected from ¹⁴C (spontaneous) cluster radioactivity from radium isotopes of the uranium and thorium natural series. Received: 15 February 1999     

Application of Experimental Design to the Optimization of a Wet Acid Digestion Procedure for Cd Determination in Plastic Materials by Atomic Absorption Spectrometry

ABSTRACT

A simple and reliable method for Cd determination in plastic materials using optimized wet acid digestion procedure and atomic absorption spectroscopy was developed. In order to obtain the best experimental conditions for plastic digestion, a 2^7–4 Plackett-Burman design for screening the significant factors and a 2^4–1 central composite design to optimize the significant experimental variables were carried out. The polyethylene European Reference Material ERM-EC680 with certified Cd content was used in both the screening and the optimization steps. The optimized experimental conditions 0.200 g of plastic material digested with 2 mL nitric acid (30 min, 130°C) followed by 1 mL sulfuric acid (30 min, 140°C). The accuracy and precision was checked using ERM-EC680. The Cd recovery was 101.3% and the relative standard deviation was 5.6%. The limit of detection obtained was 0.23 mg kg^?1. The method was applied in the analysis of one PVC plastic material, several commercial packaging materials, and plastic toys.     

Measurement of number density of lead and thallium see-through hollow cathode discharges with a high resolution Fabry–Pérot spectrometer and by conventional atomic absorption

A see-through hollow cathode lamp, or galvatron, is investigated. A novel method is presented for the measurement of an atomic absorption profile using a quasi-continuum source created by the combination of two line sources and a high-resolution Fabry–Pérot interferometer coupled to a spectrometer. Number densities are calculated from the resulting absorption profiles by the peak absorption coefficient relationship and compare well with results obtained from high-resolution emission measurements. Number densities are also determined for the lead ³ P ₁ metastable state and thallium ² P _1/2 ^o ground state by conventional atomic absorption. A hollow cathode lamp is used as an emission source and is set at a relatively low current to approximate as a line source relative to the galvatron. Due to the relative line widths of the source and absorber, only the lead metastable state results compare to results obtained by saturated fluorescence. PACS 52.25.Tx; 32.70.Jz; 07.60.Ly     

The Significance of Thermally-Assisted Processes in Atomic Absorption

The use of non-resonance lines in atomic absorption spectroscopy has been included in the theoretical treatment of the selection of lines for A.A.S.^1,2, and such lines are not infrequently used on an empirical basis in practical analyses. This aspect of the technique is invariably ignored in reviews and text-books on atomic absorption, however, and has only been given serious consideration in isolated cases^3,4. The object of this publication is to illustrate the significance of thermally-assisted absorption, and the difference between the use of thermally-assisted and resonance absorption lines.     

Kaon absorption from kaonic atoms and formation spectra of kaonic nuclei

We considered the kaon absorption from atomic states into the nucleus. We found that the nuclear density probed by the atomic kaon significantly depends on the kaon orbit. Then, we re-examined the meanings of the observed strengths of one-body and two-body kaon absorption, and investigated the effects to the formation spectra of kaon bound states by in-flight (K ^-, p) reactions. As a natural consequence, if the atomic kaon probes a smaller nuclear density, the ratio of the two-body absorption at nuclear center is larger than the observed value in kaonic atoms, and the depth of the imaginary potential is deeper even at smaller kaon energies as in kaonic nuclear states because of the large phase space for the two-body processes. This deeper imaginary potential makes the signals of kaonic nucleus formation more unclear in the (K ^-, p) spectra.     

Die Anlagerung radioaktiver Atome an Aerosole (Schwebstoffe)

The attachment of the decay products of thorium emanation to aerosol particles has been studied. The dependence of the attached activity on the particle size was determined for spherical particles with radiiR ranging from 0·04 to 0·6 microns. The particles used were homogeneous dioctylphthalate droplets and polystyrene micro-spheres. It is found that the attached activity is proportional toR ²/(1+hR). This dependence can be derived theoretically by considering the deposition to be solely governed by the diffusion process (not by electrostatic forces) and assuming a quasi-stationary density distribution for the diffusing atoms. The constanth is uniquely determined by the average gaskinetic velocity and the diffusion constant of the diffusing atoms. For the decay products of thorium and radium emanation (atomic weight ≈210)h ≈ 7 · 10⁴ cm^?1. The derived equation holds for a wide range of particle sizes: For the particles with radii larger than about 10^?4 cm this means that the attachment is proportional to the radius; for particle radii below about 10^?6 cm it is proportional to the surface (R²) of the particles. It is also possible to derive an expression for the time-dependence of the attachment process from the theoretical considerations. The rate at which the average concentration of the radioactive atoms decreases is proportional to exp ?t/τ where τ=1+hR/πR² N¯ v (¯ v=average gaskinetic velocity of the diffusing atoms;N=aerosol concentration).     

IR absorption and Raman spectra of single crystals of stable germanium isotopes

The Raman and IR absorption spectra of single crystals of germanium isotopes ⁷²Ge, ⁷³Ge, ⁷⁴Ge, and ⁷⁶Ge in the region of phonon absorption and interband electronic transitions are studied at room temperature. The dependence of the Raman peak position on the atomic mass has the form ν ~ M^–1/2. The shifts of the phonon absorption peaks of individual isotopes with respect to germanium of natural isotopic composition ^natGe are determined. With increasing average atomic mass of germanium, these peaks shift to longer wavelengths. In the region of interband electronic transitions, the intrinsic absorption edge of ⁷⁶Ge is observed to shift by 1 meV to higher energies with respect to Ge of natural isotopic composition. For isotopes with atomic masses close to that of natural germanium (⁷²Ge,⁷³Ge, ⁷⁴Ge), we found no significant difference in the band gap width at room temperature.     

Pulsed dye laser absorption spectroscopy with metastable and excited mercury atoms

A nitrogen-pumped tunable dye laser is used as a spectrometer. It is especially well suited for spectral profile study of absorption lines starting from short-lived atomic levels. Up to now, in order to illustrate its feasibility, we have measured absorption profiles for the lines 4047 Å (7³S₁ ← 6³P₀) and 4358 Å (7³S₁ ← 6³P₁) of mercury.     

Study of the partitioning of uranium and thorium in moroccan black shale

Moroccan black shale was analysed for uranium and thorium isotopes using alpha-spectrometry. A sequential leaching procedure was used to define the speciation of isotopes of the actinides in the material. As in most other organic rich rocks, uranium is highly enriched in the black shale. This actinide is associated predominantly with humic acids. Thorium (²³²Th) is a less mobile radionuclide in this environment as was expected from its chemical properties, and in agreement with the most widely adopted views in the published literature. It is partitioned between silicate minerals, pyrite and kerogen.     

Study of the partitioning of uranium and thorium in Moroccan black shale

Moroccan black shale was analysed for uranium and thorium isotopes using alpha-spectrometry. A sequential leaching procedure was used to define the speciation of isotopes of the actinides in the material. As in most other organic rich rocks, uranium is highly enriched in the black shale. This actinide is associated predominantly with humic acids. Thorium (²³²Th) is a less mobile radionuclide in this environment as was expected from its chemical properties, and in agreement with the most widely adopted views in the published literature. It is partitioned between silicate minerals, pyrite and kerogen.     

Selective Quantification of Trace Silver in Water Samples by Displacement Solidified Floating Organic Drop Microextraction Coupled With Electrothermal Atomic Absorption Spectrometry

ABSTRACT

In this work, a novel displacement solidified floating organic drop microextraction (D-SFODME) technique was developed and coupled with electrothermal atomic absorption spectrometry (ETAAS) for the determination of trace silver in water samples without need of any masking agents. The method involved the formation of copper diethyldithiocarbamate (Cu–DDTC), extracted from the resultant Cu–DDTC with SFODME procedure using 1-undecanol. Then, the solidified floating organic drop was transferred into a sample solution containing silver ion, and another SFODME procedure was carried out. Trace Ag⁺ was selectively preconcentrated using 1-undecanol through a displacement reaction between Ag⁺ and the preconcentrated Cu-DDTC and the floating organic drop was diluted by ethanol for ETAAS detection. Interferences from coexisting heavy metal ions with lower stability of their DDTC complexes relative to Cu-DDTC were minimized. Under the optimal conditions, the limit of detection was 4.7 ng L^?1 (3σ) for silver with a sample volume of 5.0 mL, and an enrichment factor of 250 was achieved. The relative standard deviation under optimum conditions is 3.6% (n = 7). The proposed method was successfully applied to determine trace silver in some environmental samples with satisfactory results.     

Optically stimulated luminescence dating of Holocene alluvial fans,East Anatolian Fault System,Turkey

In this study, the optically stimulated luminescence dating technique was used to determine the time of deposition of alluvial sediment samples from the Türko?lu-Antakya segment of the East Anatolian Fault System (EAFS) in Turkey. The double-single aliquot regenerative dose protocol on fine grain samples was used to estimate equivalent doses (D_e). Annual dose rate was computed using elemental concentration of uranium (U) and thorium (Th) determined by using thick-source alpha counting and potassium (K) concentrations using X-ray fluorescence and/or atomic absorption spectroscopy. The environmental dose was measured in situ using α-Al₂O₃:C chips inside plastic tubes for a year. The two different bulk sediment samples collected from the Islahiye trench yielded ages of 4.54?±?0.28 and 2.91?±?0.23?ka. We also obtained a 2.60?±?0.18?ka age for the alluvial deposit in the K?ranyurdu trench and 2.31?±?0.14?ka age for an excavation area called Malzeme Oca??. These ages were consistent with the corresponding calibrated Carbon-14 (¹⁴C) ages of the region. The differences between the determined ages were insufficient to clearly distinguish the disturbance event from the effects of bioturbation, biological mixing, or other sources of D_e variation in the region. They provide a record of alluvial aggradation in the region and may determine undocumented historical earthquake events.