The rotational spectrum,nuclear spin—spin coupling,nuclear quadrupole coupling,and molecular structure of KrHF

Rotational spectra have been assigned for the ⁸²Kr, ⁸³Kr, ⁸⁴Kr, and ⁸⁶Kr isotopic species of the KrHF and KrDF van der Waals molecules by using pulsed microwave Fourier transform spectroscopy in a Fabry—Perot cavity with a pulsed supersonic nozzle molecular source. The rotational, centrifugal distortion, nuclear spin—spin, and nuclear quadrupole coupling constants are used to determine the structure and obtain intramolecular potential binding information. The ⁸³Kr nuclear quadrupole coupling constants are 10.28 ± 0.08 MHz and 13.83 ± 0.13 MHz for KrHF and KrDF respectively. The electric field gradient at the krypton nucleus is calculated from the coupling constant and the known nuclear quadrupole moment and explained by Sternheimer shielding and formation of the van der Waals bond. There is a negligible charge transfer in the KrHF bond.     

Effect of Ar/H2 and Kr/H2 mixtures as discharge gas on the ion intensity in dc glow discharge mass spectrometry

 In dc glow discharge mass spectrometry, the addition of small amounts of H₂ to pure Ar as discharge gas has greatly increased the ion intensities of elements compared with the conventional method using pure Ar. This phenomenon was also observed for the addition of H₂ to pure Kr. The reason for the increase of the ion intensities of elements was studied by using a Kr gas mixture containing 0.2% (v/v) H₂. The ion intensities of the elements P, Se and As (whose first ionization potentials are higher than the energy levels of the excited state of Kr) did not increase even if the Kr/H₂ gas mixture was used. The results show that the addition of H₂ significantly contributed to increasing the number of metastable argon or krypton atoms (Penning ionization). Received: 4 November 1995/Revised: 5 January 1996/Accepted: 10 January 1996     

Effect of Ar/H2 and Kr/H2 mixtures as discharge gas on the ion intensity in dc glow discharge mass spectrometry

 In dc glow discharge mass spectrometry, the addition of small amounts of H₂ to pure Ar as discharge gas has greatly increased the ion intensities of elements compared with the conventional method using pure Ar. This phenomenon was also observed for the addition of H₂ to pure Kr. The reason for the increase of the ion intensities of elements was studied by using a Kr gas mixture containing 0.2% (v/v) H₂. The ion intensities of the elements P, Se and As (whose first ionization potentials are higher than the energy levels of the excited state of Kr) did not increase even if the Kr/H₂ gas mixture was used. The results show that the addition of H₂ significantly contributed to increasing the number of metastable argon or krypton atoms (Penning ionization). Received: 4 November 1995/Revised: 5 January 1996/Accepted: 10 January 1996     

Krypton isotopic signature study of the primary coolant of CANDU nuclear power plant

To support interpretation of observed atmospheric krypton radioisotopes, a database of krypton radioisotope in the primary coolant of CANDU reactors has been established. This database is comprised of 40,000 records of high-quality ⁸⁹Kr, ⁸⁷Kr, ⁸⁸Kr and ^85mKr analyses. Records from the database were retrieved by a specifically designed data-mining module and subjected to further analysis. Results from the analysis were subsequently used to study isotopic ratios of observed krypton radioisotopes in the CANDU reactor primary coolant. These studies provided practical information on the characterization of CANDU reactor krypton radioisotope, which can potentially be used to discriminate between reactor effluent and fuel reprocessing for nuclear safeguard ⁸⁵Kr monitoring applications (Kalinowski et al., J Environ Radioact 73:203, 2004). The study also has some potential application to Fissile material cut-off treaty.     

Detection and quantification capabilities for 85Kr with the NIST low-level gas counting system: Impacts of instrumental and environmental backgrounds

Among the most important, conservative geochemical tracers are the long-lived isotopes of krypton, ⁸¹Kr and ⁸⁵Kr. Following a brief review of the metrology and applications of these radionuclides, we focus on the low-level measurement of the 10.8 year fission product ⁸⁵Kr, in connection with its use for studying atmospheric transport and short term (decadal) atmosphere-ocean exchange and mixing. Special challenges for the study of ⁸⁵Kr in the environment are: (1) reducing detection/quantification limits to mBq levels, to minimize the need for costly (large) atmospheric and marine samples, where current levels are ca. 1.4 Bq·m^-3 (northern troposphere) and 0.08 mBq·kg^-1 (surface ocean water); and (2) designing a protocol that accounts for the influence of both instrumental and environmental backgrounds and their variability. The capability of the NIST enhanced low-level gas counting system to meet these challenges was demonstrated theoretically and experimentally, showing that ambient ⁸⁵Kr can be quantified in just 1.5 l air or 25 l seawater with 2000 min paired counting periods.     

Counting Radio-Krypton Atoms with a Laser

Because of their unique chemical and physical properties, long-lived rare krypton radioisotopes, ⁸⁵Kr and ⁸¹Kr, are ideal tracers for environmental samples, including air, groundwater and ice. Atom trap trace analysis (ATTA) is a new laser-based method for counting both ⁸⁵Kr and ⁸¹Kr atoms with the abundance as low as 10^-14 with micro-liters (STP) krypton gas. The entire system for rare radio-krypton measurement built at Hefei is presented, including the atom trap trace analysis instrument and sampling apparatus of gas extraction from water and krypton purification. Atmospheric⁸⁵Kr concentrations at different places in China were measured, showing a range of 1.3-1.6 Bq/m³, consistent with the northern hemispheric baseline. As a demonstration of the system, some shallow and deep groundwater samples in north and south China were sampled and dated.     

83Kr nuclear magnetic moment in terms of that of 3He

High resolution NMR spectroscopy was applied to precisely determine the ⁸³Kr nuclear magnetic dipole moment on the basis of new results available for nuclear magnetic shielding in krypton and helium‐3 atoms. Small amounts of ³He as the solutes and ⁸³Kr as the buffer gas were observed in ³He and ⁸³Kr NMR spectra at the constant external field, B₀ = 11.7578 T. In each case, the resonance frequencies (ν^He and ν^Kr) were linearly dependent on the density of gaseous solvent. The extrapolation of experimental points to the zero density of gaseous krypton allowed for the evaluation of both resonance frequencies free from intermolecular interactions. By combining these measurements with the recommended ⁸³Kr chemical shielding value, the nuclear magnetic moment could be determined with much better precision than ever before, μ(⁸³Kr) = ?0.9707297(32)μ_N, with the improvement due to the greater accuracy of the spectral data. Copyright © 2014 John Wiley & Sons, Ltd.     

Separation of Xe from Kr with Record Selectivity and Productivity in Anion‐Pillared Ultramicroporous Materials by Inverse Size‐Sieving

The separation of xenon/krypton (Xe/Kr) mixture is of great importance to industry, but the available porous materials allow the adsorption of both, Xe and Kr only with limited selectivity. Herein we report an anion‐pillared ultramicroporous material NbOFFIVE‐2‐Cu‐i (ZU‐62) with finely tuned pore aperture size and structure flexibility, which for the first time enables an inverse size‐sieving effect in separation along with record Xe/Kr selectivity and ultrahigh Xe capacity. Evidenced by single‐crystal X‐ray diffraction, the rotation of anions and pyridine rings upon contact of larger‐size Xe atoms adapts cavities to the shape/size of Xe and allows strong host‐Xe interaction, while the smaller‐size Kr is excluded. Breakthrough experiments confirmed that ZU‐62 has a real practical potential for producing high‐purity Kr and Xe from air‐separation byproducts, showing record Kr productivity (206 mL g^?1) and Xe productivity (42 mL g^?1, in desorption) as well as good recyclability.     

83 Kr Nuclear quadrupole coupling in KrHF: evidence for charge transfer

The ⁸³Kr nuclear quadrupole coupling constant in KrHF has been measured to be x = 10.227(71) MHz. Using the known ⁸³Kr nuclear quadrupole moment, the field gradient at the Kr nucleus is evaluated and interpreted in terms of charge transfer in the weak Kr-HF van der Waals bond. Rotational assignments are reported for ⁸²Kr, ⁸³Kr, ⁸⁴Kr, and ⁸⁶Kr isotopic KrHF.     

纳秒激光电离产生Kr17+的研究

Up to Kr17 + multicharged krypton ions have been observed in time-of-flight mass spectrum by a 25 ns Nd-YAG 1. 064 μm laser at laser intensity about 1012 W/ cm2 . Experimental results indicate that the multicharged ions appear only when the laser interacts with the middle part of the pulsed beam,and the intensities of the multicharged ions increase dramatically by increasing the backing pressure of Kr gas,which indicates that the clusters in the beam is essential to the production of multicharged ions. From the experimental results,it is concluded that the cluster is ionized via multiphoton ionization and forms a nanoplasma ball,which can absorb the laser resonantly to further ionize the single charge ion to the high charge state.     

Determination of low level85Kr and133Xe concentrations in the environment

This study was performed under the joint TRMC/INER program for the determination of low level⁸⁵Kr and¹³³Xe concentrations in the environmental air samples. Based on cryogenic adsorption of krypton and xenon on charcoal followed by chromatographic separation from other gases, the⁸⁵Kr and¹³³Xe recovered from 200 liters of atmospheric air can be determined by either on-line gas flow proportional counter or liquid scintillation counting. The recovery yields of krypton and xenon examined by using⁸⁵Kr and¹³³Xe tracers were nearly 100%. The minimum detectable activity of⁸⁵Kr and¹³³Xe by gas flow proportional counting is about 7.40 Bq. The method is satisfactory for environmental monitoring applications under abnormal conditions of nuclear facilities. However, for lower level environmental⁸⁵Kr and¹³³Xe measurements, the liquid scintillation counting method can be applied due to their extremely low detection limits (i.e. 0.107 Bq and 0.093 Bq for⁸⁵Kr and¹³³Xe, respectively). Using this method, the measurable limits of concentrations are 0.535 Bq/m³ and 0.466 Bq/m³ for⁸⁵Kr and¹³³Xe, respectively.     

Detection of reprocessing activities through stable isotope measurements of atmospheric noble gases

Noble gas stable isotope abundance measurements may provide a tool for detecting reprocessing activities of nuclear fuels. An approach has been made by carrying out blending calculations of released fission xenon and krypton in air using the Isotope Mixture Programs which have been developed at the IRMM. After having obtained a reliable approximation to the expected range of the isotope ratios in the blends and the respective detection limit thereof through these calculations, the potential application of ultra-accurate measurements of the isotopic composition of anthropogenic and atmospheric noble gases is taken into consideration. Also the important role of radiometric measurements of ⁸⁵Kr and ¹³³Xe for the detection of nuclear fuel reprocessing is taken into account. The information provided by such activity measurements is limited, therefore a method to calculate the initial isotopic composition of released fission noble gases, through measuring of their atmospheric mixing ratio, is presented and discussed. Highly accurate stable isotopic measurements of atmospheric noble gases might provide more detailed information on the “history” of the reprocessed nuclear fuel. Therefore they could serve, in combination with radiometric detection techniques, as an excellent tool for the identification of reprocessing activities.     

Applications of gas chromatography and gamma spectrometry to fission gas measurements

A gas sampler with lead shield has been designed for transferring the grab gas sample taken from the sampling station of Taiwan nuclear power reactor. The methods involving gas chromatography and gamma spectrometry have been developed for the determination of fission gases. A gas chromatograph equipped with TCD was used for measurement of gas composition. Column requirements are identified and optimum operating conditions are discussed. A single analysis is completed within 25 minutes for all of the gas constitutents and 12 minutes for only Xe and Kr. The detection limit is 0.005 mm partial pressure for Kr and Xe and a precision of ±1% relative is achieved for all the sample constituents. Combined error determinations for the method denote an attainable accuracy of less than ±2% for constituents at a sample pressure above 10 mm. Mixing and dispensing of the radioactive gases were carried out in a special gas mixing line. In experiment, calibration factors for measurement of¹³³Xe and⁸⁵Kr in ampules are determined in an isotope calibrator and by Ge(Li) gamma ray spectrometry. The relative precisions of 0.14% and 0.5% are readily achieved for⁸⁵Kr and¹³³Xe, respectively. The calibration uncertainty in⁸⁵Kr measurement is 0.4%.     

Intra‐ and inter‐tooth variation in strontium isotope ratios from prehistoric seals by laser ablation multi‐collector inductively coupled plasma mass spectrometry

Rationale

Strontium isotope ratios (⁸⁷Sr/⁸⁶Sr) in modern‐day marine environments are considered to be homogeneous (~0.7092). However, in the Baltic Sea, the Sr ratios are controlled by mixing seawater and continental drainage from major rivers discharging into the Baltic. This pilot study explores if variations in Sr can be detected in marine mammals from archaeological sites in the Baltic Sea.

Methods

⁸⁷Sr/⁸⁶Sr ratios were measured in tooth enamel from three seal species by laser ablation multi‐collector inductively coupled plasma mass spectrometry (LA‐MC‐ICP‐MS). The method enables micro‐sampling of solid materials. This is the first time that the method has been applied to marine samples from archaeological collections.

Results

The analyses showed inter‐tooth ⁸⁷Sr/⁸⁶Sr variation suggesting that different ratios can be detected in different regions of the Baltic Sea. Furthermore, the intra‐tooth variation suggests possible different geographic origin or seasonal movement of seals within different regions in the Baltic Sea through their lifetime.

Conclusions

The method was successfully applied to archaeological marine samples showing that: (1) the ⁸⁷Sr/⁸⁶Sr ratio in marine environments is not uniform, (2) ⁸⁷Sr/⁸⁶Sr differences might reflect differences in ecology and life history of different seal species, and (3) archaeological mobility studies based on ⁸⁷Sr/⁸⁶Sr ratios in humans should therefore be evaluated together with diet reconstruction.

     

Storage possibilities for radioactive krypton (85Kr)

A review of the different storage possibilities for radioactive krypton (⁸⁵Kr) is given. Various strategies can be applied to store⁸⁵Kr safely over many decades: storage in pressure containers and encapsulation in various solid matrices.     

Solubility and Thermodynamics of Solvation of Krypton in Mixtures of H/D Isotopomers of Water and Methanol at 101325 Pa and 278-318 K

The solubility of krypton in mixtures of H/D isotopomers of water (H₂O, D₂O) and methanol (CH₃OH, CD₃OH, CH₃OD) was studied at 101325 Pa and 278.15-318.15 K with a 10 K step. The thermodynamic characteristics of Kr solvation were calculated. The densities of mixtures of water and methanol isotopomers at the examined temperatures were calculated with an error of no more than 1 × 10^{- 5} g cm^{- 3} in the entire composition range. Both in water and aqueous methanol, krypton behaves as a structure-making component, but the alcohol solvation surrounding of the Kr atoms is more labile and more susceptible to the breaking effect of temperature.     

Comparative studies on excitation of nickel ionic lines between argon and krypton glow discharge plasmas

The emission characteristics of nickel ionic lines in a glow discharge plasma are investigated when argon or krypton was employed as the plasma gas. Large difference in the relative intensities of nickel ionic lines which are assigned to the 3d⁸4p–3d⁸4s transition is observed between the krypton plasma and the argon plasma. Different intense Ni II lines appear in the krypton spectrum and in the argon spectrum, such as the Ni II 231.601 nm for Kr and the Ni II 230.009 nm for Ar. The excitation energy of these Ni II emission lines can give a key in considering their excitation mechanisms. The explanation for these experimental results is that charge-transfer collisions between nickel atom and the plasma gas ion play a major role in exciting the 3d⁸4p excited levels of nickel ion. The conditions for energy resonance in the charge-transfer collision determine particular energy levels having much larger population; for example, the 3d⁸4p ⁴D_7/2 level (6.39 eV) for Kr and the 3d⁸4p ⁴P_5/2 level (8.25 eV) for Ar.     

Efficient Separation of Ar and Kr from Environmental Samples for Trace Radioactive Noble Gas Detection

Radioactive noble-gas isotopes, ⁸⁵Kr (half-life t_1/2=10.8 y), ³⁹Ar (t_1/2=269 y), and ⁸¹Kr (t_1/2=229,000 y), are ideal tracers and can be detected by atom trap trace analysis (ATTA), a laser-based technique, from environmental samples like air and groundwater. Prior to ATTA measurements, it is necessary to efficiently extract krypton and argon gases from samples. Using a combination of cryogenic distillation, titanium chemical reaction and gas chromatography, we demonstrate that we can recover both krypton and argon gases from 1-10 L "air-like" samples with yields in excess of 90% and 98%, respectively, which meet well the requirements for ATTA measurements. A group of testing samples are analyzed to verify the performance of the system, including two groundwater samples obtained from north China plain.     

An automated microprocessor controlled system for the production of a new type of81Rb−81mKr generator

Routine production of⁸¹Rb, utilizing the⁸²Kr(p, 2n)⁸¹Rb reaction with natural krypton gas is described. Development and construction of a fully automated gas target system controlled by microprocess or is presented. A new type of⁸¹Rb–^81mKr generator based on the sorption of⁸¹Rb on ion-exchange paper was developed and investigated in operation. It may be used either for gas-phase or for liquid elution of^81mKr for different medical applications.     

Advancement of isotope separation for the production of reference standards

Idaho National Laboratory (INL) operates a mass separator that is currently producing high purity isotopes for use as internal standards for high precision isotope dilution mass spectrometry (IDMS). In 2008, INL began the revival of the vintage 1970s era instrument. Advancements thus far include the successful upgrading and development of system components such as the vacuum system, power supplies, ion-producing components, and beam detection equipment. Progress has been made in the separation and collection of isotopic species including those of Ar, Kr, Xe, Sr, and Ba. Particular focuses on ion source improvements and developments have proven successful with demonstrated output beam currents of over 10 μA ¹³⁸Ba and 350 nA ¹³⁴Ba from a natural abundance Ba source charge (~2.4 % ¹³⁴Ba). In order to increase production and collection of relatively high quantities (mg levels) of pure isotopes, several improvements have been made in ion source designs, source material introduction, and ion detection and collection. These improvements have produced isotopes of high purity (>98 %) and in quantities in the tens of micrograms per run. The instrument and results for pure isotope production for IDMS standards will be presented.