Showing papers in "Journal of Physical and Chemical Reference Data in 2015"
TL;DR: Theoretical energy levels of the n = 1 and n = 2 states of hydrogen-like atoms with the nuclear charge numbers 1 ≤ Z ≤ 110 are tabulated in this article.
Abstract: Theoretical energy levels of the n = 1 and n = 2 states of hydrogen-like atoms with the nuclear charge numbers 1 ≤ Z ≤ 110 are tabulated. The tabulation is based on ab initio quantum electrodynamics calculations performed to all orders in the nuclear binding strength parameter Zα, where α is the fine structure constant. Theoretical errors due to various effects are critically examined and estimated.
118 citations
TL;DR: A review of literature on enthalpies of formation and molar entropies for alkanes, alkenes, alcohols, hydroperoxides, and their associated radicals has been compiled and critically evaluated.
Abstract: A review of literature on enthalpies of formation and molar entropies for alkanes, alkenes, alcohols, hydroperoxides, and their associated radicals has been compiled and critically evaluated. By comparing literature values, the overall uncertainty in thermochemical properties of small hydrocarbons and oxygenated hydrocarbons can be highlighted. In general, there is good agreement between heat of formation values in the literature for stable species; however, there is greater uncertainty in the values for radical species and for molar entropy values. Updated values for a group-additivity method for the estimation of thermochemical properties based on the evaluated literature data are proposed. The new values can be used to estimate thermochemical data for larger, combustion-relevant species for which no calculations or measurements currently exist, with increased confidence.
94 citations
TL;DR: In this article, cross section data are compiled from the literature for electron collisions with methane (CH4) molecules and cross sections are collected and reviewed for total scattering, elastic scattering, momentum transfer, excitations of rotational and vibrational states, dissociation, ionization, and dissociative attachment.
Abstract: Cross section data are compiled from the literature for electron collisions with methane (CH4) molecules Cross sections are collected and reviewed for total scattering, elastic scattering, momentum transfer, excitations of rotational and vibrational states, dissociation, ionization, and dissociative attachment The data derived from swarm experiments are also considered For each of these processes, the recommended values of the cross sections are presented The literature has been surveyed through early 2014
74 citations
TL;DR: In this paper, a recommended value for the proton root-mean-square charge radius, rE = 0.879 ± 0.011 fm, based on a global examination of elastic e-p scattering data is provided.
Abstract: In light of the proton radius puzzle, the discrepancy between measurements of the proton charge radius from muonic hydrogen and those from electronic hydrogen and electron–proton (e–p) scattering measurements, we re-examine the charge radius extractions from electron scattering measurements. We provide a recommended value for the proton root-mean-square charge radius, rE = 0.879 ± 0.011 fm, based on a global examination of elastic e–p scattering data. The uncertainties include contributions to account for tension between different data sets and inconsistencies between radii using different extraction procedures.
48 citations
TL;DR: In this article, the current status of the theory of bound-electron g factor in highly charged ions is presented, and the calculations of the relativistic, quantum electrodynamics (QED), nuclear recoil, nuclear structure, and interelectronic-interaction corrections to the g factor are reviewed.
Abstract: The paper presents the current status of the theory of bound-electron g factor in highly charged ions. The calculations of the relativistic, quantum electrodynamics (QED), nuclear recoil, nuclear structure, and interelectronic-interaction corrections to the g factor are reviewed. Special attention is paid to tests of QED effects at strong coupling regime and determinations of the fundamental constants.
45 citations
TL;DR: In 2011, a discrepancy between the values of the Planck constant measured by counting Si atoms and by comparing mechanical and electrical powers prompted a review of the measurement of the spacing of 28Si {220} lattice planes, either to confirm the measured value and its uncertainty or to identify errors as mentioned in this paper.
Abstract: In 2011, a discrepancy between the values of the Planck constant measured by counting Si atoms and by comparing mechanical and electrical powers prompted a review, among others, of the measurement of the spacing of 28Si {220} lattice planes, either to confirm the measured value and its uncertainty or to identify errors. This exercise confirmed the result of the previous measurement and yields the additional value d220 = 192 014 711.98(34) am having a reduced uncertainty.
43 citations
TL;DR: In this article, a critical review of experimental measurements and ab-initio calculations of shear viscosity and self-diffusion coefficients is presented for variable soft sphere (VSS) and Lennard-Jones (L-J) models for eight common gases in the temperature range 20-2200 K.
Abstract: Revised parameters for variable soft sphere (VSS) and Lennard-Jones (L-J) (6-12) models are presented for eight common gases in the temperature range 20–2200 K The new parameters are based on a critical review of experimental measurements and ab-initio calculations of shear viscosity and self-diffusion coefficients The optimized parameters are assessed relative to experimental measurements and ab-initio calculations of thermal conductivity Results indicate most significant improvements for the VSS model occur when considering lighter gases where repulsive forces are more important The agreement with transport property measurements for He gas extends to much higher temperatures using the revised parameters The accuracy of the L-J model is more significantly improved when considering the heavier gases for which attractive forces are important over a wider temperature range
34 citations
TL;DR: In this paper, a new representation of the viscosity for the fluid phase of ethane includes a zero-density correlation and a contribution for the critical enhancement, initially both developed separately, but based on experimental data.
Abstract: A new representation of the viscosity for the fluid phase of ethane includes a zero-density correlation and a contribution for the critical enhancement, initially both developed separately, but based on experimental data. The higher-density contributions are correlated as a function of the reduced density δ = ρ/ρc and of the reciprocal reduced temperature τ = Tc/T (ρc—critical density and Tc—critical temperature). The final formulation contains 14 coefficients obtained using a state-of-the-art linear optimization algorithm. The evaluation and choice of the selected primary data sets is reviewed, in particular with respect to the assessment used in earlier viscosity correlations. The new viscosity surface correlation makes use of the reference equation of state for the thermodynamic properties of ethane by Bucker and Wagner [J. Phys. Chem. Ref. Data 35, 205 (2006)] and is valid in the fluid region from the melting line to temperatures of 675 K and pressures of 100 MPa. The viscosity in the limit of zero de...
33 citations
TL;DR: In this article, a review of recent calculations of the Lamb shift in muonic hydrogen is presented, including pure quantum electrodynamics (QED) ones as well as those which involve the proton-structure effects.
Abstract: There has been for a while a large discrepancy between the values of the proton charge radius measured by the Lamb shift in muonic hydrogen and by other methods. It has already been clear that theory of muonic hydrogen is reliable at the level of this discrepancy and an error there cannot be a reason for the contradiction. Still the status of theory at the level of the uncertainty of the muonic-hydrogen experiment (which is two orders of magnitude below the discrepancy level) requires an additional clarification. Here, we revisit theory of the 2p − 2s Lamb shift in muonic hydrogen. We summarize all the theoretical contributions in order α5m, including pure quantum electrodynamics (QED) ones as well as those which involve the proton-structure effects. Certain enhanced higher-order effects are also discussed. We basically confirm former QED calculations of other authors, present a review of recent calculations of the proton-structure effects, and treat self-consistently higher-order proton-finite-size corre...
32 citations
TL;DR: In this article, a new fundamental equation of state explicit in the Helmholtz energy is presented for 1,1, 1,3,3-pentafluoropropane (R-245fa), based on recent experimental data for vapor pressures, densities, and sound speeds.
Abstract: A new fundamental equation of state explicit in the Helmholtz energy is presented for 1,1,1,3,3-pentafluoropropane (R-245fa), based on recent experimental data for vapor pressures, densities, and sound speeds. The functional form uses Gaussian bell-shaped terms, according to recent trends in the development of accurate equations of state. The independent variables of the equation of state are temperature and density. The equation is valid for temperatures between the triple point (170.0 K) and 440 K, and for pressures up to 200 MPa. Estimated uncertainties in this range are 0.1% for vapor pressures, 0.1% for saturated liquid densities, 0.1% for liquid densities below 70 MPa, 0.2% for densities at higher pressures, 0.3% for vapor densities, 0.3% for liquid sound speeds, and 0.1% for vapor sound speeds. The uncertainties in the critical region are higher for all properties except vapor pressures. The equation shows reasonable extrapolation behavior at extremely low and high temperatures, and at high pressures.
30 citations
TL;DR: In this paper, the authors focus their attention on refrigerants and propose specific correlations to reproduce the surface tension values for several sets of fluids and for wide ranges of temperatures, using the data available for 86 refrigerant fluids using recent versions of the DIPPR and DETHERM databases as main sources.
Abstract: In previous papers, some of us have proposed specific correlations to reproduce the surface tension values for several sets of fluids and for wide ranges of temperatures. In this paper, we focus our attention on refrigerants. In particular, we consider the data available for 86 refrigerant fluids using recent versions of the DIPPR and DETHERM databases and the book of Wohlfarth and Wohlfarth (1997) as main sources. In some cases, new data available have been added from other sources, with these data being appropriately selected. In some cases, two or more different trends of data were observed, and, where possible, the authors have considered only one of those trends. To fit the data finally considered, we used the same model as currently used in REFPROP program of the National Institute of Standards and Technology. Two or four adjustable coefficients were needed for the refrigerants we studied. For three of these fluids, it was not possible to obtain an adequate fit to the selected data. We have therefore proposed correlations for 83 refrigerants, giving mean average percentage deviations below 2.7%.
TL;DR: In this article, it has been observed that quantum-mechanical interference between neighboring resonances can cause significant shifts, even if such neighbouring resonances are separated by thousands of natural widths.
Abstract: For many decades, improvements in both theory and experiment of the fine structure of the n = 2 triplet P levels of helium have allowed for an increasingly precise determination of the fine-structure constant. Recently, it has been observed that quantum-mechanical interference between neighboring resonances can cause significant shifts, even if such neighboring resonances are separated by thousands of natural widths. The shifts depend in detail on the experimental method used for the measurement, as well as the specific experimental parameters employed. Here, we review how these shifts apply for the most precise measurements of the helium 23P fine-structure intervals.
TL;DR: Theoretical results for the isotope shift of the centroid energies of light few-electron atoms are presented in this article, where the difference of the squares of the nuclear charge radii of 3He and 4He, δR2, is determined with high accuracy.
Abstract: Theory of the isotope shift of the centroid energies of light few-electron atoms is reviewed. Numerical results are presented for the isotope shift of the 23P-23S and 21S-23S transition energies of 3He and 4He. By comparing theoretical predictions for the isotope shift with the experimental results, the difference of the squares of the nuclear charge radii of 3He and 4He, δR2, is determined with high accuracy.
TL;DR: In this paper, an additional value of the Avogadro constant was obtained by counting the atoms in isotopically enriched Si spheres with respect to the previous determination, the spheres were etched and repolished to eliminate metal contaminations and to improve the roundness.
Abstract: An additional value of the Avogadro constant was obtained by counting the atoms in isotopically enriched Si spheres. With respect to the previous determination, the spheres were etched and repolished to eliminate metal contaminations and to improve the roundness. In addition, all the input quantities—molar mass, lattice parameter, mass, and volume—were remeasured aiming at a smaller uncertainty. In order to make the values given in Andreas et al. [Metrologia 48, S1 (2011)] and Azuma et al. [Metrologia 52, 360 (2015)] usable for a least squares adjustment, we report about the estimate of their correlation.
TL;DR: In this paper, the authors focus their attention on alcohols and consider the available data for 152 fluids grouped into five families, and propose recommended correlations for 147 alcohols, providing mean average percentage deviations below 1.7% for each fluid, with only two exceptions: 1,2-butanediol (2.77%) and benzyl alcohol (3.20%).
Abstract: In previous papers, we have proposed specific correlations to reproduce the surface tension values for several sets of fluids and for wide ranges of temperatures. In this paper, we focus our attention on alcohols and consider the available data for 152 fluids grouped into five families. We use the most recent versions of the DIPPR and DETHERM databases and also Wohlfarth and Wohlfarth’s (1997) book as our main sources of data. In some cases we have also considered new data. All the data have been carefully filtered in order to discard those that are in clear disagreement with most of the available data for the same fluid. In some cases, two or more different data sets versus temperature trends were observed, and where possible we considered only one of these trends. To fit the finally selected data, we used the model currently implemented in National Institute of Standards and Technology’s refprop program, calculating two, four, or six adjustable coefficients for each fluid. As a result, we proposed recommended correlations for 147 alcohols, providing mean average percentage deviations below 1.7% for each fluid, with only two exceptions: 1,2-butanediol (2.77%) and benzyl alcohol (3.20%).
TL;DR: The most recent tabulations of nuclear magnetic dipole and electric quadrupole moments have been prepared and published by the Nuclear Data Section of the IAEA, Vienna as discussed by the authors.
Abstract: The most recent tabulations of nuclear magnetic dipole and electric quadrupole moments have been prepared and published by the Nuclear Data Section of the IAEA, Vienna [N. J. Stone, Report No. INDC(NDS)-0650 (2013); Report No. INDC(NDS)-0658 (2014)]. The first of these is a table of recommended quadrupole moments for all isotopes in which all experimental results are made consistent with a limited number of adopted standards for each element; the second is a combined listing of all measurements of both moments. Both tables cover all isotopes and energy levels. In this paper, the considerations relevant to the preparation of both tables are described, together with observations as to the importance and (where appropriate) application of necessary corrections to achieve the “best” values. Some discussion of experimental methods is included with emphasis on their precision. The aim of the published quadrupole moment table is to provide a standard reference in which the value given for each moment is the best available and for which full provenance is given. A table of recommended magnetic dipole moments is in preparation, with the same objective in view.
TL;DR: In this paper, the Doppler-free spectroscopy of the 1S-3S transition in hydrogen has been investigated and a new continuous ultra-violet source has been developed and delivered a power level of 15 mW.
Abstract: We report the latest advances in the Doppler-free spectroscopy of the 1S–3S transition in hydrogen. A new continuous ultra-violet source has been developed and delivers a power level of 15 mW. With this setup, the statistical uncertainty on the 1S–3S transition frequency measurement is 2.2 kHz. Combined with the 1S–2S frequency, absolute accuracy at that level would significantly enlighten the proton radius puzzle.
TL;DR: The anomalous magnetic moment of the muon is one of the most precisely measured quantities in experimental particle physics as mentioned in this paper, and its latest measurement at Brookhaven National Laboratory deviates from the Standard Model expectation by approximately 3.5 standard deviations.
Abstract: The anomalous magnetic moment of the muon is one of the most precisely measured quantities in experimental particle physics. Its latest measurement at Brookhaven National Laboratory deviates from the Standard Model expectation by approximately 3.5 standard deviations. The goal of the new experiment, E989, now under construction at Fermilab, is a fourfold improvement in precision. Here, we discuss the details of the future measurement and its current status.
TL;DR: In this paper, a wide range of reference equations for the thermal conductivity of cyclopentane, iso-pentane, and n -pentane are presented, based on a body of experimental data that has been critically assessed for internal consistency and for agreement with theory whenever possible.
Abstract: New, wide-range reference equations for the thermal conductivity of cyclopentane, iso-pentane, and n-pentane are presented. The equations are based in part upon a body of experimental data that has been critically assessed for internal consistency and for agreement with theory whenever possible. In the case of the dilute-gas thermal conductivity, a theoretically based correlation was adopted in order to extend the temperature range of the experimental data. In the critical region, the enhancement of the thermal conductivity is well represented by theoretically based equations containing just one adjustable parameter, estimated by a predictive scheme. The thermal-conductivity equations behave in a physically reasonable manner over a wide range of conditions that correspond to the range of validity of the most accurate equations of state for each fluid. The estimated uncertainties of the correlations are dependent on the availability of accurate experimental data for validation, and are different for each fluid, varying from 1% (at the 95% confidence level) for the liquid phase of iso-pentane over the temperature range 307 K
TL;DR: In this article, the authors examined how IAPWS-95 behaves with respect to the experimental data published after 1995 and showed that it is able to represent the latest experimental data for the density, expansivity, compressibility, speed of sound, and isobaric heat capacity to within the uncertainties given in the release.
Abstract: Over the past several years, considerable scientific and technical interest has been focused on accurate thermodynamic properties of fluid water covering part of the subcooled (metastable) region and the stable liquid from the melting line up to about 300 K and pressures up to several hundred MPa. Between 2000 and 2010, experimental density data were published whose accuracy was not completely clear. The scientific standard equation of state for fluid water, the IAPWS-95 formulation, was developed on the basis of experimental data for thermodynamic properties that were available by 1995. In this work, it is examined how IAPWS-95 behaves with respect to the experimental data published after 1995. This investigation is carried out for temperatures from 250 to 300 K and pressures up to 400 MPa. The starting point is the assessment of the current data situation. This was mainly performed on the basis of data for the density, expansivity, compressibility, and isobaric heat capacity, which were derived in 2015 from very accurate speed-of-sound data. Apart from experimental data and these derived data, property values calculated from the recently published equation of state for this region of Holten et al. (2014) were also used. As a result, the unclear data situation could be clarified, and uncertainty values could be estimated for the investigated properties. In the region described above, detailed comparisons show that IAPWS-95 is able to represent the latest experimental data for the density, expansivity, compressibility, speed of sound, and isobaric heat capacity to within the uncertainties given in the release on IAPWS-95. Since the release does not contain uncertainty estimates for expansivities and compressibilities, the statement relates to the error propagation of the given uncertainty in density. Due to the lack of experimental data for the isobaric heat capacity for pressures above 100 MPa, no uncertainty estimates are given in the release for this pressure range. Results of the investigation of IAPWS-95 concerning its behavior with regard to the isobaric heat capacity in the high-pressure low-temperature region are also presented. Comparisons with very accurate speed-of-sound data published in 2012 showed that the uncertainty estimates of IAPWS-95 in speed of sound could be decreased for temperatures from 283 to 473 K and pressures up to 400 MPa.
TL;DR: In this paper, the determination of electromagnetic form factors from the world data on electron-nucleus scattering for nuclei Z ≤ 3 was discussed, with particular emphasis on the moments required for comparison with measurements from electronic/muonic atoms and isotope shifts.
Abstract: We discuss the determination of electromagnetic form factors from the world data on electron–nucleus scattering for nuclei Z ≤ 3, with particular emphasis on the derivation of the moments required for comparison with measurements from electronic/muonic atoms and isotope shifts.
TL;DR: The history of estimation of the heliocentric gravitational constant is given in this paper, where the value of GM was based on the mean period of motion of the Earth around the Sun, and finally the modern value was determined with extraordinarily high accuracy, GM⊙ = 132.712, 440,042 ± 10 (km3/s2).
Abstract: The history of estimation of the heliocentric gravitational constant is given. Initially the value of GM⊙ was based on the mean period of motion of the Earth around the Sun, then on estimation of the value of the astronomical unit, and finally the modern value of GM⊙ is determined with the extraordinarily high accuracy, GM⊙ = 132 712 440 042 ± 10 (km3/s2), while fitting ephemerides to high-precision radar observations.
TL;DR: In this article, the current situation in studies of lifetimes of excited rovibronic levels for the H2, D2, T2, HD, HT, and DT molecules is analyzed.
Abstract: The current situation in studies of lifetimes of excited rovibronic levels for the H2, D2, T2, HD, HT, and DT molecules is analyzed. All measured lifetime values (792 entries for 618 different vibro-rotational levels of 33 electronic states) reported in 61 publications before April 2015 are compiled and listed in tabular format together with an annotated bibliography. Experimental data are only available for the H2, HD, and D2 molecules. The data collected in the present work show fragmentariness of experimental data. For the vast majority of the levels, the lifetime values were reported in one paper only and up to now are without independent experimental verification. A complete bibliography of publications concerning semiempirical determination and nonempirical calculations of the lifetimes is presented. Numerical results obtained in the framework of these two approaches are listed only in cases when experimental data are available. For more than half of the levels, the differences between measured and calculated values are three times higher than experimental errors. These discrepancies show necessity of more precise experimental and nonempirical studies. For some 79 rovibronic levels, our analysis makes it possible to propose certain set of recommended lifetime values.
TL;DR: In this article, a detailed examination of issues associated with proton radius extractions from elastic electron-proton scattering experiments is presented, with an emphasis on how these may impact the proton charge and magnetic radii.
Abstract: A detailed examination of issues associated with proton radius extractions from elastic electron–proton scattering experiments is presented. Sources of systematic uncertainty and model dependence in the extractions are discussed, with an emphasis on how these may impact the proton charge and magnetic radii. A comparison of recent Mainz data to previous world data is presented, highlighting the difference in treatment of systematic uncertainties as well as tension between different data sets. We find several issues that suggest that larger uncertainties than previously quoted may be appropriate, but do not find any corrections which would resolve the proton radius puzzle.
TL;DR: In this article, a new correlation for the viscosity of para-xylene was proposed, which is applicable in the temperature range from the triple point to 673 K at pressures up to 110 MPa.
Abstract: A new correlation for the viscosity of para-xylene (p-xylene) is presented. The correlation is based upon a body of experimental data that has been critically assessed for internal consistency and for agreement with theory. It is applicable in the temperature range from the triple point to 673 K at pressures up to 110 MPa. The overall uncertainty of the proposed correlation, estimated as the combined expanded uncertainty with a coverage factor of 2, varies from 0.5% for the viscosity of the dilute gas to 5% for the highest temperatures and pressures of interest. Tables of the viscosity generated by the relevant equations, at selected temperatures and pressures and along the saturation line, are provided.
TL;DR: In this paper, a new experiment which reduces possible systematic uncertainties of the Positronium thermalization effect and nonuniformity of magnetic field was performed, and revealed that the Ps thermalisation effect was as large as 10 ± 2 ppm.
Abstract: Positronium (Ps) is an ideal system for precision test of bound state quantum electrodynamics. The hyperfine splitting (HFS) of the ground state of Ps, which is one of the most precisely tested quantity, has a large discrepancy of 16 ppm (4.5 σ) between previous experiments and theoretical calculation up to O(α3lnα−1) and part of O(α3) corrections. A new experiment which reduces possible systematic uncertainties of Ps thermalization effect and nonuniformity of magnetic field was performed. It revealed that the Ps thermalization effect was as large as 10 ± 2 ppm. Treating the thermalization effect correctly, a new result of 203.3942 ± 0.0016(stat., 8.0 ppm) ± 0.0013(sys., 6.4 ppm) GHz was obtained. This result is consistent with theory within 1.1 σ, whereas it disfavors the previous experimental result by 2.6 σ. It shows that the Ps thermalization effect is crucial for precision measurement of HFS. Future prospects for improved precision are briefly discussed.
TL;DR: A brief overview of the existing systematics on nuclear mean square charge radii, obtained by a combined analysis of data from different types of experiment is given in this paper, where various techniques yielding data on nuclear charge radius are summarized and their specific feature complexities and the accuracy and precision of the obtained information are discussed.
Abstract: This paper is a brief overview of the existing systematics on nuclear mean square charge radii, obtained by a combined analysis of data from different types of experiment The various techniques yielding data on nuclear charge radii are summarized Their specific feature complexities and the accuracy and precision of the obtained information are also discussed
TL;DR: A brief overview of the presentations at the workshop on the determination of the fundamental constants (Eltville, 2015) and the contributions to the proceedings can be found in this article, with a discussion of the main themes of the workshop.
Abstract: We present a brief overview of the presentations at the workshop on the determination of the fundamental constants (Eltville, 2015) and the contributions to the proceedings.