The elemental and isotopic determination of lithium by the coincidence measurement of complementary particles

The coincident measurement of both nuclear products at their complementary angles was used to determine⁶Li by the reactions⁶Li(d, α)⁴He and⁶Li(p, α)³He, and⁷Li by the reaction⁷Li(p, α)⁴He. Elemental lithium was determined in natural samples or samples of known isotopic composition. Isotopic analyses could be carried out over the entire range from 0 to 100 atom% with a relative standard deviation of about 4%. The CMCP technique is highly specific and effectively eliminates interference and background.     

Estimation of isotopic composition of plutonium from thermal reactors by neutron coincidence counting through isotopic correlation technique

Correlations have been established between %Eff ²⁴⁰Pu and various plutonium isotopes formed in thermal reactors. Based on these correlations, a method has been developed for the estimation of isotopic composition of plutonium obtained from thermal reactors. The method is simple, fast, non-destructive and finds application for the verification of plutonium isotopic composition in the finished products of known plutonium content. The method could be applied in the nuclear fuel fabrication to verify and confirm the fissile content (²³⁹Pu+²⁴¹Pu) specification. It has also been shown that in principle, similar correlations could be established for Pu obtained from different thermal reactor fuels with reactor specific fitting parameters.     

Carbon isotopic composition effects on interatomic interactions and the properties of diamond

The interatomic interaction potential parameters were determined for ¹²C and ¹³C in diamond. The results were used to obtain the isotopic dependences of such diamond properties as the Debye temperature, molar heat capacity, thermal expansion coefficient, energies of vacancy formation and self-diffusion, surface energy, and longitudinal velocity of sound. The isotopic dependence of isochoric heat capacity disappeared as the temperature increased. Sign inversion was observed for the isotopic dependence of the thermal expansion coefficient at a certain temperature: its growth changed into a drop. This approach was also used to estimate changes in the interatomic interaction potential and crystal bulk compression modulus of lithium in going from ⁷Li to ⁶Li. The isotopic dependences of phase transition parameters and the whole p-T phase diagram of a simple substance were predicted.     

Determination of traces of bismuth by isotopic exchange reaction in the organic phase

A new radioanalytical method has been developed based on homogeneous isotopic exchange in the organic phase. The theory of the method is presented and discussed. This method has been applied for the simple, selective and rapid determination of bismuth based on the isotopic exchange between bismuth diethyldithiocarbamate and bismuth iodide complex labelled with²¹⁰Bi. As little as 0.01 μg of the metal can be determined.     

EPR studies of isotopic exchange involving adsorbed oxygen species on MgO

In the EPR spectra of ¹⁷O₂^? adsorbed on MgO, the hyperfine lines due to ¹⁷O(I = $\text{5}\text{2}$) have been used to monitor the isotopic exchange with gas phase oxygen. The predicted behaviour of the different possible mechanisms (place exchange and/or isotopic exchange) is compared with the experimental results which show that, on MgO at room temperature, isotopic exchange occurs via an intermediate species which is tentatively identified as O₄^?.     

Round robin for uranium isotopic measurements by mass spectrometry

A round-robin for uranium isotopic analysis in two solutions with different concentrations prepared and certified by the Institute for Reference Materials and Measurements (IRMM, Geel, Belgium) was organized by CETAMA, a division of the Commissariat à l’énergie Atomique (CEA: French Atomic Energy Commission Fourteen laboratories took part in the program using twenty-five different instruments (ICP-QMS, ICP-SFMS and TIMS). For each solution and each isotopic ratio, a statistical analysis based on standard ISO 5725 was carried out to calculate the mean, the repeatability and reproducibility standard deviations, the z-score and zeta-score, the bias with respect to the target values, and to compare their precision. The mean measurement results for the ²³⁴U/²³⁸U and ²³⁵U/²³⁸U isotopic ratios show no significant biases compared with the target values, whatever is the analytical technique. The results were much less satisfactory for the ²³⁶U/²³⁸U isotopic ratio, for which only the laboratories specialized in traces analyses and/or precise isotopic analyses submitted results in good agreement with the target values. A detailed discussion is given in this article.     

An inter-calibration campaign using various selected Pu spike isotopic reference materials

In nuclear safeguards, precise and accurate isotopic analyses are needed for two major elements from the nuclear fuel cycle: uranium and plutonium. This can be achieved by Isotope Dilution Mass Spectrometry (IDMS), which is one of the most reliable analytical techniques for the determination of plutonium amount content to a high level of accuracy. In order to achieve reliable isotope measurements isotopic reference materials with certified amount of plutonium and isotopic composition are required. At the Institute for Reference Materials and Measurements (IRMM) various plutonium spike reference materials for isotopes ²³⁹Pu, ²⁴⁰Pu, ²⁴²Pu and ²⁴⁴Pu are available. This enabled the setup of an inter-calibration campaign inter-linking selected plutonium spikes on a metrological basis applying state-of-the-art measurement procedures. The aim of this campaign is threefold: firstly to perform measurements on selected plutonium spike isotopic reference materials for quality control purposes, secondly to verify the amount content and the isotopic composition of the recently produced IRMM-1027m large sized dried (LSD) spikes and thirdly to demonstrate IRMM’s measurement capabilities for plutonium analysis via external quality tools. The obtained results using various spike isotopic reference materials will be presented and discussed in this paper. The measurement uncertainties of the IDMS results were calculated according to the guide to the expression of uncertainty in measurement (GUM).     

Separation of radionuclides by isotopic exchange using metal chelates and fixed metal sulphide precipitates

The possibilities of radioanalytical separation by isotopic exchange with metal chelate complexes and metal sulphide precipitates fixed in paper have been examined on the model system²⁰³Hg²⁺+⁵⁸Co²⁺+⁶⁵Zn²⁺+²⁴Na⁺.     

Substitution kinetics of chelate complexes as studied by isotopic exchange

The fact that isotopic exchange reactions take place at chemical equilibirum makes this type of reaction useful for kinetic studies. In the case of chelate complexes [M(chel)_n] isotopic exchange reactions can be classified as metal exchange reactions. [M(chel)_n]+^*M⇆[^*M(chel)_n]+M and ligand exchange reactions [M(chel)_n]+^*chel⇆[M(chel)_n−1 ^*chel]+chel The literature on type (a) and type (b) reactions of mainly transition metal complexes is reviewed with respect to the kinetic information obtained. The value and the limitations of isotopic exchange studies as a kinetic technique are discussed.     

Ultratrace analysis of calcium with high isotopic selectivity by diodelaser resonance ionisation mass spectrometry

A resonance ionisation mass spectrometer for the ultratrace determination of calcium isotopes is presented. It achieves high overall efficiency, ultra-high isotopic abundance sensitivity of more than 10¹⁰ and complete suppression of isobars. The system can be used for isotope ratio studies on stable and long-lived trace isotopes with the final goal of radiodating via ⁴¹Ca-determination. For the different applications optical one-, two- or three-step resonance excitation and subsequent ionisation is applied using simple and inexpensive diodelasers. Additional mass analysis is accomplished in a commercial quadrupole mass spectrometer. The experimental set-up and first results on synthetical and meteorite samples are described.     

A magnetic isotopic effect in the triplet sensitized photolysis of dibenzoyl peroxide

A ¹³C isotopic effect was detected in the triplet sensitized photolysis of dibenzoyl peroxide. Analysis of ¹³C NMR spectra shows that the amount of ¹³C in position 1 of phenyl benzoate, the cage product, increase by 23 ± 5% in comparison with natural abundance. The observed isotopic effect considerably exceeds the known ${}^{12}\text{C}{}^{13}\text{C}$ kinetic isotopic effects. This effect is believed to be magnetic in origin and is explained in terms of the dependence of the recombination probabilities of radical pairs in the cage on the electron-nuclear hyperfine interaction.     

Determination of isotopic composition of boron

Investigations were carried out on the determination of isotopic composition of boron using Cs₂BO ₂ ⁺ ion and thermal ionisation mass spectrometry. The results show distinct advantage over the normally used Na₂BO ₂ ⁺ ion.     

Evaluation of a new generation quadrupole-based ICP-MS for uranium isotopic measurements in environmental samples

We compare the analytical performance of a modern quadrupole-based ICP-MS (“X-Series”, Thermo-Electron, Winsford, UK) with a single-collector double-focusing sector-field ICP-MS (“Axiom”, VG Elemental, Winsford, UK) for uranium isotopic measurements in environmental samples. We focus on the precision and accuracy obtained with both instruments for the ²³⁵U/²³⁸U isotopic ratios and on the abundance sensitivity that is a key parameter for low ²³⁶U/²³⁸U isotopic ratios measurements. We observe that isotopic measurements are more precise accurate with the “X-Series” than with the “Axiom”. Besides, we demonstrate that the “Axiom’s” higher abundance sensitivity limits its capability to measure ²³⁶U/²³⁸U ratio below a few ppm.     

Gadolinium isotopic measurements by surface ionization mass spectrometry

Gadolinium isotope ratio measurements were carried out by single filament thermal ion source, with the addition of colloidal carbon as surface and chemical modifier. The technique becomes an interesting alternative to classical single filament GdO⁺ and triple filament Gd⁺ analysis. The methodology developed has been applied to a sample containing Gd₂O₃ which was converted to nitrate before loading it on a rhenium filament. Optimum Gd⁺ ion signal is produced at a temperature of 1470C. The measured mean isotopic ratios agree with the representative isotopic composition reviewed and reported by IUPAC. Typical relative external standard deviations of 0.2% are attainable for the¹⁵⁷Gd abundance.     

High resolution infrared analyses of fundamentals and overtones in isotopic ketenes

Rovibrational structure in the ν₅, ν₆, ν₇, ν₈ fundamentals and 2ν₅, 2ν₆ overtones in each of H₂¹²C¹²CO, H₂¹²C¹³CO, H₂¹³C¹²CO has been assigned and analysed. The effects of Fermi resonance between ν₇ and ν₂+ν₈ are corrected for, and a set of accurate unperturbed vibrational frequencies and ¹³C isotopic frequency shifts therefrom is obtained. The changing effects of the major Coriolis interactions involving the out-of-plane fundamentals, ν₅ and ν₆, are manifest in varying isotopic displacements of equivalent Q branch structures between the isotopic species studied, from which accurate isotopic vibrational shifts are obtained. Variable anharmonicity constants associated with the vibration frequencies of 2ν₅ and 2ν₆ give evidence of major Fermi resonance interactions between both overtones and the ν₄ fundamental, which they straddle.     

Sensitivity of magneto-optic rotation to variations in isotopic composition

The technique has the advantage of allowing isotopic differences to be detected using a standard atmospheric atomiser and a conventional hollow cathode source. The measurements are sufficiently robust to tolerate a limited variability of sample composition, background absorption from matrix species, and some instrumental parameters such as source intensity. Different isotopes show different responses with varying magnetic field strength across the atomiser. This allows a distinction to be made between the isotopes even though only a single source of natural isotopic composition is used. Results illustrating this behaviour are given for Pb²⁰⁶, Pb²⁰⁷, Pb²⁰⁸.     

Crystal hydration and vacancy enhanced isotopic exchange reactions in heterogeneous solid-liquid systems

The rate of some heterogeneous isotopic exchange reactions can be enhanced by the simultaneous hydration of the solid participating in the exchange process. The results presented here show that the concomitant hydration of anhydrous sodium sulphate enhances the Na₂SO₄–²²Na⁺ isotopic exchange reaction in a water-acetone medium. The reaction rate is further enhanced by creating a controlled number of vacancies in the crystal lattice of sodium sulphate by doping.     

The isotopic mass defect: a tool for limiting molecular formulas by accurate mass

This paper describes the use of the relative isotopic mass defect, which is the mass defect between the monoisotopic mass of an element and the mass of its A + 1 or its A + 2 isotopic cluster. The relative isotopic mass defect is combined with the intensity of the isotopic cluster and a formula generator to find the correct molecular formula for unknown pesticides, using accurate mass measurements. This paper introduces the concept of the relative mass defect of isotopes and the isotopic mass average (IMA), especially for C, H, N, O, S, Cl, and Br, and how to correlate these measurements to the correct molecular formula of an unknown compound. A heuristic rule of ±3 × 10⁻³ u (+3 millimass units) is developed as a simple observational tool for viewing accurate mass data with four-decimal-place mass accuracy. This heuristic rule allows one to rapidly scan data “by eye” without the use of sophisticated software, and is a useful and rapid way of examining a molecular formula.     

Low frequency raman spectra of isotopic mixed benzophenone crystals

In this paper, we present an experimental study of vibrational lattice modes in isotopic mixed crystals of benzophenone-h₁₀ and -d₁₀. Our results are discussed using theoretical and experimental data concerning other molecular isotopic mixed crystals. The spectra show two regions; in the first (ν < 100 cm^?1) we did not observe an interaction between the various vibrational lattice bands; in the second region (ν > 100 cm^?1), the interaction appears clearly. The 111.5 cm^?1 and 73 cm^?1 torsional modes of benzophenone-h₁₀ have the same behaviour as the external modes throughout the whole concentration range (0–100% of benzophenone-d₁₀).     

Semiclassical calculation of vibrational relaxation of CO colliding with 4He and 3He

The rate constant for the deactivation of CO (υ = 1) colliding with ⁴He and ³He is calculated in the range 100–1000 K. Agreement with experiment can be obtained using a hybrid isotropic potential. The isotopic ratio k₁₀(³He) k₁₀(⁴He) is predicted to be strongly temperature dependent at low temperatures.