甲烷中微量噻吩气体标准物质研制

研制了甲烷中噻吩气体标准物质。以高纯噻吩、高纯甲烷为原材料，包装容器为4 L内壁经抛光处理的铝合金瓶，通过微量转移与常规相结合的方法完成了甲烷中微量噻吩气体标准物质制备。利用气相色谱法对标准物质进行了均匀性检验及稳定性考察。F检验和回归曲线法实验结果表明，该气体标准物质在压力为0.5～10 MPa范围内，均匀性良好，在常温条件下保存12个月稳定。采用称量法对该气体标准物质进行了定值，并对定值、均匀性和稳定性引入的不确定度进行了评定，该系列甲烷中微量噻吩气体标准物质标称摩尔分数为1.00～10.0μmol/mol，定值结果的相对扩展不确定度为2%(k=2)。     

甲烷中甲硫醇气体标准物质的研制

以甲硫醇钠为原料，通过与稀硫酸反应制备甲硫醇。对甲硫醇和甲烷分别进行纯化，采用气相色谱-火焰光度检测器与气相色谱法氦离子放电检测器对纯化后的甲硫醇和甲烷进行纯度分析，甲硫醇纯度（摩尔分数）为99.75%，甲烷纯度（摩尔分数）为99.997%。通过称量法制备了甲烷中甲硫醇气体标准物质。采用气相色谱法火焰光度检测器对标准物质进行了均匀性检验、稳定性考察。研制的甲烷中甲硫醇标准物质标称浓度为100μmol/mol,F检验和回归曲线法实验结果表明，在压力0.5～10 MPa范围内，该标准物质具有良好的均匀性和稳定性，定值结果的相对扩展不确定度为2%(k=2)，有效期为12个月。     

二氧化碳中一氧化氮气体标准物质研制

研制二氧化碳中一氧化氮气体标准物质。以高纯二氧化碳和一氧化氮气体标准物质为原料,采用称量法制备二氧化碳中一氧化氮气体标准物质,用气体分析仪对制备的标准物质浓度进行检测,并对该标准物质定值结果的不确定度进行评定。研制的二氧化碳中一氧化氮气体标准物质中一氧化氮的浓度为5,25,50 μmol/mol,相对扩展不确定度为3.0% (k=2)。该气体标准物质具有良好的均匀性和稳定性,可用于食品级二氧化碳分析方法的确认和评价。     

氩气中一氧化碳、二氧化碳、甲烷、乙烷混合气体标准样品的研制

介绍气体报警仪标定和检测使用的氩气中一氧化碳、二氧化碳、甲烷、乙烷气体标准样品的制备,以气相色谱法对其均匀性和稳定性进行考核,对定值结果的不确定度进行了评定。标准气体定值范围:一氧化碳为500～1000μmol/mol,不确定度2%;二氧化碳为1000～5000μmol/mol,不确定度2%;甲烷为300～500μmol/mol,不确定度3%;乙烷为300～500μmol/mol,不确定度3%。     

空气中偏二甲肼气体标准物质的研制

采用称量法制备空气中偏二甲肼气体标准物质,分别用F检验和回归曲线法对研制的标准物质进行均匀性和稳定性检验。结果表明,研制的空气中偏二甲肼气体标准物质具有良好的均匀性和稳定性,定值结果分别为10,500μmol/mol,定值结果的相对扩展不确定度为2%(k=2)。该标准物质可用于偏二甲肼报警器的检定或校准。     

电力变压器油中溶解气体分析用标准物质的研制

采用称量法制备了电力变压器油中溶解气体分析用气体标准物质,分别用F检验和回归曲线法对研制的标准物质进行了均匀性和稳定性检验。结果表明,研制的电力变压器油中溶解气体分析用标准物质具有良好的均匀性和稳定性,标准物质定值结果为5 000μmol/mol,定值结果的相对扩展不确定度为1%(k=2)。该标准物质可用于电力部门变压器油中溶解气体的分析及测试。     

氮中甲烷气体标准物质的研制

以甲烷纯度标准物质和高纯氮气为原料,采用称重法制备氮中甲烷气体标准物质。称量过程考虑了空气密度、天平线性系数、气瓶体积膨胀系数、转移和装卸过程产生的质量损失等因素。用气相色谱仪测定了高纯氮气中甲烷的含量,并对研制的标准物质进行了压力均匀性和时间稳定性检验。结果表明,研制的氮中甲烷气体标准物质标准值为10.0~1.00×10~3μmol/mol(U_(rel)=2%,k=2),该标准物质具备良好的均匀性和稳定性,可用于测量仪器的校准、测量过程的质量控制及分析方法的确认和评价。     

氮气中1 μmol·mol~(-1)硫化氢气体标准物质的研制

介绍了瓶装氮气中1μmol·mol-1硫化氢气体标准物质的研制过程,对称量法制备过程、均匀性、稳定性引入的不确定度进行了评定。该气体标准物质的相对扩展不确定度为Uc=2.0%,k=2,使用有效期为一年,取得了国家一级标准物质证书。     

氮中丙烯腈气体标准物质的研制

以高纯丙烯腈和高纯氮气为原料,采用称量法配制氮中丙烯腈气体标准物质。对配制的气体标准物质分别进行机械混匀试验、压力均匀性和时间稳定性试验。经F检验,2.00μmol/mol及5.00μmol/mol两种浓度的样品在0.5~10 MPa范围内标准值无显著变化,具有较好的压力均匀性;在–20℃和40℃条件下保存7 d,其量值无显著变化,可满足运输环节量值稳定;在常温下贮存9个月量值无显著变化,表明其稳定性良好,满足国家二级标准物质对有效期的要求。对定值结果的不确定度进行评定。配制的氮中丙烯腈气体标准物质标准值为(2~5)×10~(–6)mol/mol,相对扩展不确定度为9%(k=2)。该标准物质达到国家二级标准物质的相关技术要求,可用于对丙烯腈气体报警器的校准。     

氮气中六氟化硫气体标准物质的研制

建立了制备氮气中六氟化硫气体标准物质的方法。以称量法制备气体标准物质并计算定值,采用气相色谱法对制备的气体标准物质的均匀性和稳定性进行考察。将所制备的标准物质与中国计量院提供的氮气中六氟化硫气体标准物质进行比对分析验证,确保了气体标准物质量值的准确可靠。结果表明,所研制的浓度为10μL/L的氮气中六氟化硫气体标准物质定值的扩展不确定度为2%,贮存有效期为1年,完全能够满足电力部门仪表的检定与校准要求。     

Correlation factor for ground state of helium

If a variational trial function of form exp(–ar ₁ –ar ₂)f(r ₁₂) is postulated for the ground-state of helium-like ions, then for a given a it is shown that the variation principle leads to an ordinary second order differential equation for f, the solution of which represents the optimum function f for use with a trial function of this type, in the sense that this solution minimises the expectation value of the Hamiltonian for the system. A solution to the differential equation may be found by the usual series expansion method.

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Zusammenfassung Wenn ein Variationsansatz der Form exp(–ar ₁ –ar ₂ f(r ₁₂) für den Grundzustand von Heartigen Ionen vorausgesetzt wird, so wird gezeigt, daß (bei gegebenem a) das Variationsprinzip zu einer gewöhnlichen Differentialgleichung 2. Ordnung für f führt. Ihre Lösung stellt eine optimale, den Erwartungswert des Hamiltonoperators des Systems minimisierende Funktion des angegebenen Typs dar. Eine Lösung der Differentialgleichung kann mit der gewöhnlichen Methode eines Reihenentwicklungs-Ansatzes gefunden werden.

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Résumé Si l'on prend comme fonction variationnelle d'essai pour l'état fondamental des ions de type hélium: exp(–ar₁ –ar ₂)f(r ₁₂) le principe variationnel mène pour a constant à une équation différentielle du second ordre pour f. La solution de cette équation représente la «meilleure» fonction f à utiliser avec une fonction d'essai de ce type, car elle minimise la valeur moyenne de l'hamiltonien. Cette solution peut être obtenue par la méthode ordinaire de développement en série.

     

Deltafunction model for the helium dimer

The helium dimer ⁴He₂ has recently been detected, confirming earlier ab initio predictions of stability for a single bound state with binding energy of 1.310 mK. The predicted potential minimum is at 2.96 Å, with a radial distribution function peaking at 6.96 Å. We model this system using a Dirac bubble potential, which also admits just one bound j = 0 state. With the bubble located at 6.96 Å, an overlap of 0.9994 with the ab initio wave function is obtained. An average internuclear distance of 52.6 Å is calculated, in good agreement with the ab initio result. The root mean square deviation from the mean, 48.0 Å, indicates an enormous spread of the radial wave function. Also consistent with our model is the absence of bound states for the isotopic variants ³He⁴He and ³He₂. Cross sections for helium-helium scattering are also computed, using both a partial-wave expansion and the Born approximation. General trends in the energy dependence of the total cross section are accounted for, in qualitative agreement with experimental results. © 1995 John Wiley & Sons, Inc.     

Correlation holes for the helium dimer

We have investigated the radial electron pair probability distributions (REPPDs) of the helium dimer within the Piris natural orbital functional (PNOF) theory. The analytical formulas to evaluate intracule densities, Fermi, Coulomb, and total correlation holes using our reconstruction functional PNOF-2 [J. Chem. Phys. 126, 214103 (2007)] are derived. The L?wdin's Coulomb holes from PNOF-2 and full configuration interaction calculations are analyzed showing a very similar behavior. New definitions of the Coulomb and Fermi holes based on the cumulant expansion of the two-particle reduced density matrix are presented. The holes are defined in terms of the exact one-particle reduced density matrix and the two-particle cumulant without any reference to the Hartree-Fock state. Through these definitions, we analyze separately the contribution of each component to the total REPPD at several values of the internuclear distance. A straight connection between the Coulomb hole and dispersion interactions is observed.     

Charge transfer to helium ions from metastable helium

The cross section for charge transfer in He⁺He(2³S) collisions is calculated using the asymptotic theory of ion-atom interactions, including the effects of polarization and momentum transfer. The results agree well with recent measurements by the merged beam technique.     

MNDO parameters for helium: Optimization,tests, and application to endohedral fullerene—helium complexes

MNDO parameters for helium are derived from an optimization that employs only atomic and diatomic reference data. Comparisons with published high-level ab initio results indicate that MNDO correctly predicts the existence of covalently bonded helium compounds and normally reproduces the geometries of these small charged molecules reasonably well. Endohedral fullerene–helium complexes and the transition states for their formation are studied for C₆₀, C₆₀, and C. The calculated barriers are discussed and compared with those for the passage of helium through C₆H₆, C₆H, and C₆H. © 1993 John Wiley & Sons, Inc.     

Analytic functions for the three-body potential of the helium trimer

The three-body potential for the ground state of the helium trimer is determined by an extended geminal model. The basis set for the calculation is an uncontracted (19s,7p,6d,5f,4g,2h) set of Gaussian-type functions. Three different types of configurations were considered: (i) equilateral triangles, (ii) linear configurations with R12=R23, and (iii) a set of pseudorandom configurations. The interatomic distances were selected within the interval [3.0,9.0] bohrs. The computed points have been fitted to global potential functions. The fit is characterized by a maximum absolute error equal to 0.69 microEh and a mean error equal to -0.018 microEh.     

23S state of helium

A rapidly convergent method, which has previously been applied to the ground state of the helium atom, has been extended to excited S states. This method is based on an expansion of the wave function in powers of \documentclass{article}\pagestyle{empty}\begin{document}$ \sqrt {r_1^2 + r_2^2} $\end{document}, ln (r + r), \documentclass{article}\pagestyle{empty}\begin{document}$ w = r_{12} /\sqrt {r_1^2 + r_2^2} $\end{document}. Different effective nuclear charges are used for the inner and the outer electrons. Very satisfactory results are obtained for expectation values of various operators.     

A helium inductively coupled plasma for atomic emission spectrometry

An annular helium inductively coupled plasma (He ICP) was generated at atmospheric pressure. No external cooling was used to stabilize the plasma. Aqueous solution was injected into the plasma without any difficulty. Preliminary results revealed that the annular He ICP was capable of exciting elements such as Cl and Br which possess high excitation energies. Atomic emission detection limits for Cl and Br were improved by factors of 63 and 34, respectively, as compared to the results obtained from the argon inductively coupled plasma. The excitation temperature of the annular He ICP (4180 K) was less than that of an Ar ICP (5570 K).     

Contracted polarization functions for the atoms helium through neon

Contracted Gaussian-type function sets are proposed for polarization functions of the atoms helium through neon, with the exception of lithium. A segmented contraction scheme is used for its compactness and computational efficiency. The contraction coefficients and orbital exponents are fully optimized to minimize the difference from accurate atomic natural orbitals. The present polarization functions yield more than 99% of atomic correlation energies predicted by accurate natural orbitals of the same size. Received: 16 April 1997 / Accepted: 26 June 1997