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Top 20 Most Read Articles
April 2012
The 20 articles with the most full-text downloads during the month, in descending order.
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J. Phys. Chem. Ref. Data 41, 013102 (2012); http://dx.doi.org/10.1063/1.3659413 (119 pages) Online Publication Date: 2 February 2012
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Energy levels, with designations and uncertainties, have been compiled for the spectra of strontium (Z=38) ions from singly ionized to hydrogen-like. Wavelengths with classifications, intensities, and transition probabilities are also tabulated. In addition, ground states and ionization energies are listed. For many ionization stages experimental data are available; however for those for which only theoretical calculations or fitted values exist, these are reported. There are a few ionization stages for which only a calculated ionization potential is available.
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J. Phys. Chem. Ref. Data 18, 1537 (1989); http://dx.doi.org/10.1063/1.555836 (28 pages)
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In order to represent the thermodynamic properties of water (H2O) over an extremely large range of temperature and pressure that is not covered by existing equations of state, a new fundamental equation has been developed. The Helmholtz function was fitted to the following kinds of experimental data: (a) pρT data, (b) thermal properties of the saturation curve (ps,ρ′,ρ″), (c) speed of sound w, (d) isobaric heat capacity cp, (e) isochoric heat capacity cv, (f) differences of the internal energy u, (g) differences of the enthalpy h, (h) Joule–Thomson coefficient μ, and (i) the isothermal throttling coefficient δT. A new statistical selection method was used to determine the final form of the equation from a ‘‘bank’’ of 630 terms which also contained functional forms that have not been previously used. This 58‐coefficient equation covers the entire fluid region from the melting line to 1273 K at pressures up to 25 000 MPa, and represents the data within their experimental accuracy also in the ‘‘difficult’’ regions below 0 °C, on the entire saturation curve, in the critical region and at very high pressures. The equation was constrained at the critical point as defined by the parameters internationally recommended by the International Association for the Properties of Steam (IAPS). Besides the 58‐coefficient equation for the entire pressure range, a 38‐coefficient equation is presented for providing a ‘‘fast’’ equation for practical and scientific calculations in the pressure range below 1000 MPa. This equation has, with the exception of the critical region, nearly the same accuracy as the 58‐coefficient equation. The quality of the new equations will be illustrated by comparing the values calculated from them with selected experimental data and with the IAPS‐84 formulation and the Scaling‐Law equation. |
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J. Phys. Chem. Ref. Data 25, 1509 (1996); http://dx.doi.org/10.1063/1.555991 (88 pages)
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This work reviews the available data on thermodynamic properties of carbon dioxide and presents a new equation of state in the form of a fundamental equation explicit in the Helmholtz free energy. The function for the residual part of the Helmholtz free energy was fitted to selected data of the following properties: (a) thermal properties of the single‐phase region (pρT) and (b) of the liquid‐vapor saturation curve (ps, ρ′, ρ″) including the Maxwell criterion, (c) speed of sound w and (d) specific isobaric heat capacity cp of the single phase region and of the saturation curve, (e) specific isochoric heat capacity cv, (f) specific enthalpy h, (g) specific internal energy u, and (h) Joule–Thomson coefficient μ. By applying modern strategies for the optimization of the mathematical form of the equation of state and for the simultaneous nonlinear fit to the data of all these properties, the resulting formulation is able to represent even the most accurate data to within their experimental uncertainty. In the technically most important region up to pressures of 30 MPa and up to temperatures of 523 K, the estimated uncertainty of the equation ranges from ±0.03% to ±0.05% in the density, ±0.03% to ±1% in the speed of sound, and ±0.15% to ±1.5% in the isobaric heat capacity. Special interest has been focused on the description of the critical region and the extrapolation behavior of the formulation. Without a complex coupling to a scaled equation of state, the new formulation yields a reasonable description even of the caloric properties in the immediate vicinity of the critical point. At least for the basic properties such as pressure, fugacity, and enthalpy, the equation can be extrapolated up to the limits of the chemical stability of carbon dioxide. Independent equations for the vapor pressure and for the pressure on the sublimation and melting curve, for the saturated liquid and vapor densities, and for the isobaric ideal gas heat capacity are also included. Property tables calculated from the equation of state are given in the appendix. © 1996 American Institute of Physics and American Chemical Society. |
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J. Phys. Chem. Ref. Data 17, 513 (1988); http://dx.doi.org/10.1063/1.555805 (374 pages)
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Kinetic data for the radicals H⋅ and ⋅OH in aqueous solution,and the corresponding radical anions, ⋅O− and eaq−, have been critically pulse radiolysis, flash photolysis and other methods. Rate constants for over 3500 reaction are tabulated, including reaction with molecules, ions and other radicals derived from inorganic and organic solutes. |
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The spectrum of molecular nitrogen J. Phys. Chem. Ref. Data 6, 113 (1977); http://dx.doi.org/10.1063/1.555546 (195 pages)
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This is a critical review and compilation of the observed and predicted spectroscopic data on the molecule N2 and its ions N2 −, N2 +, N2 2+, and the molecule N3. Each electronic band system is discussed in detail, and tables of band origins and heads are given. In addition to the gas phase electronic, electron and Raman spectra, there are also examined the spectra of condensed molecular nitrogen as well as the pressure‐ and field‐induced infrared and microwave absorption. Dissociation energy of N2, predissociations, and perturbations are discussed. Potential energy curves are given, as well as radiative lifetimes, f‐values, and Franck‐Condon integrals. Molecular constants are listed for the known electronic states. Electronic structure and theoretical calculations are reviewed. |
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Energy Levels and Observed Spectral Lines of Neutral and Singly Ionized Titanium, Ti I and Ti II J. Phys. Chem. Ref. Data 41, 013101 (2012); http://dx.doi.org/10.1063/1.3656882 (116 pages) Online Publication Date: 12 January 2012
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The energy levels and observed spectral lines of neutral and singly ionized titanium atoms have been compiled. Tables of energy levels and spectral lines are generated for each stage. Experimental g-factors and leading percentages are included when available. An experimental value for the ionization energy for each stage is provided.
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J. Phys. Chem. Ref. Data 41, 013105 (2012); http://dx.doi.org/10.1063/1.3675992 (67 pages) Online Publication Date: 27 March 2012
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The alkaline earth carbonates are an important class of minerals. This volume compiles and critically evaluates solubility data of the alkaline earth carbonates in water and in simple aqueous electrolyte solutions. Part 1, the present paper, outlines the procedure adopted in this volume in detail, and presents the beryllium and magnesium carbonates. For the minerals magnesite (MgCO3), nesquehonite (MgCO3·3H2O), and lansfordite (MgCO3·5H2O), a critical evaluation is presented based on curve fits to empirical and/or thermodynamic models. Useful side products of the compilation and evaluation of the data outlined in the introduction are new relationships for the Henry constant of CO2 with Sechenov parameters, and for various equilibria in the aqueous phase including the dissociation constants of CO2(aq) and the stability constant of the ion pair MCO30(aq) (M = alkaline earth metal). Thermodynamic data of the alkaline earth carbonates consistent with two thermodynamic model variants are proposed. The model variant that describes the Mg2+-HCO3- ion interaction with Pitzer parameters was more consistent with the solubility data and with other thermodynamic data than the model variant that described the interaction with a stability constant.
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Physical Properties of Ionic Liquids: Database and Evaluation J. Phys. Chem. Ref. Data 35, 1475 (2006); http://dx.doi.org/10.1063/1.2204959 (43 pages) Online Publication Date: 10 October 2006
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A comprehensive database on physical properties of ionic liquids (ILs), which was collected from 109 kinds of literature sources in the period from 1984 through 2004, has been presented. There are 1680 pieces of data on the physical properties for 588 available ILs, from which 276 kinds of cations and 55 kinds of anions were extracted. In terms of the collected database, the structure-property relationship was evaluated. The correlation of melting points of two most common systems, disubstituted imidazolium tetrafluoroborate and disubstituted imidazolium hexafluorophosphate, was carried out using a quantitative structure-property relationship method.
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J. Phys. Chem. Ref. Data 39, 043101 (2010); http://dx.doi.org/10.1063/1.3309507 (942 pages) Online Publication Date: 4 October 2010
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A compendium of phase change enthalpies published within the period 1880–2010 is reported. Phase change enthalpies including fusion, vaporization, and sublimation are included for organic, organometallic, and a few inorganic compounds. This compendium is a combination of three previous series focusing on phase change enthalpies updated to 2009. Sufficient data are presently available for some compounds to permit thermodynamic cycles to be constructed, an important manner of evaluating the reliability of the measurements. Temperature adjustments of phase change enthalpies from the temperature of measurement to the standard reference temperature, T = 298.15 K, are briefly disscussed and a protocol for doing so is illustrated.
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Critically Evaluated Atomic Transition Probabilities for Sulfur S I–S XV J. Phys. Chem. Ref. Data 38, 171 (2009); http://dx.doi.org/10.1063/1.3032939 (269 pages) Online Publication Date: 5 June 2009
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Atomic transition probabilities for about 6400 allowed and forbidden lines of S I–S XV are tabulated based on a critical evaluation of recent literature sources. The transition probabilities were obtained mainly from recent sophisticated calculations carried out with complex computer codes. These tables provide data of interest for astronomical as well as laboratory plasmas. They will also be useful for the diagnostics of plasmas encountered in fusion energy research.
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J. Phys. Chem. Ref. Data 31, 387 (2002); http://dx.doi.org/10.1063/1.1461829 (149 pages) Online Publication Date: 7 June 2002
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In 1995, the International Association for the Properties of Water and Steam (IAPWS) adopted a new formulation called “The IAPWS Formulation 1995 for the Thermodynamic Properties of Ordinary Water Substance for General and Scientific Use”, which we abbreviate to IAPWS-95 formulation or IAPWS-95 for short. This IAPWS-95 formulation replaces the previous formulation adopted in 1984. This work provides information on the selected experimental data of the thermodynamic properties of water used to develop the new formulation, but information is also given on newer data. The article presents all details of the IAPWS-95 formulation, which is in the form of a fundamental equation explicit in the Helmholtz free energy. The function for the residual part of the Helmholtz free energy was fitted to selected data for the following properties: (a) thermal properties of the single-phase region (pρT) and of the vapor–liquid phase boundary (pσρ′ρ″T), including the phase-equilibrium condition (Maxwell criterion), and (b) the caloric properties specific isochoric heat capacity, specific isobaric heat capacity, speed of sound, differences in the specific enthalpy and in the specific internal energy, Joule–Thomson coefficient, and isothermal throttling coefficient. By applying modern strategies for optimizing the functional form of the equation of state and for the simultaneous nonlinear fitting to the data of all mentioned properties, the resulting IAPWS-95 formulation covers a validity range for temperatures from the melting line (lowest temperature 251.2 K at 209.9 MPa) to 1273 K and pressures up to 1000 MPa. In this entire range of validity, IAPWS-95 represents even the most accurate data to within their experimental uncertainty. In the most important part of the liquid region, the estimated uncertainty of IAPWS-95 ranges from ±0.001% to ±0.02% in density, ±0.03% to ±0.2% in speed of sound, and ±0.1% in isobaric heat capacity. In the liquid region at ambient pressure, IAPWS-95 is extremely accurate in density (uncertainty ⩽±0.0001%) and in speed of sound (±0.005%). In a large part of the gas region the estimated uncertainty in density ranges from ±0.03% to ±0.05%, in speed of sound it amounts to ±0.15% and in isobaric heat capacity it is ±0.2%. In the critical region, IAPWS-95 represents not only the thermal properties very well but also the caloric properties in a reasonable way. Special interest has been focused on the extrapolation behavior of the new formulation. At least for the basic properties such as pressure and enthalpy, IAPWS-95 can be extrapolated up to extremely high pressures and temperatures. In addition to the IAPWS-95 formulation, independent equations for vapor pressure, the densities, and the most important caloric properties along the vapor–liquid phase boundary, and for the pressure on the melting and sublimation curve, are given. Moreover, a so-called gas equation for densities up to 55 kg m−3 is also included. Tables of the thermodynamic properties calculated from the IAPWS-95 formulation are listed in the Appendix. © 2002 American Institute of Physics. |
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J. Phys. Chem. Ref. Data 40, 043105 (2011); http://dx.doi.org/10.1063/1.3664915 (19 pages) Online Publication Date: 30 December 2011
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The available thermodynamic-property data for solid phase I of carbon dioxide (“dry ice”) are reviewed and used to determine the parameters of a new fundamental equation of state constructed in the form of a Helmholtz energy function with temperature and molar volume as the independent variables. The experimental data considered include the pressure, molar volume, and isobaric heat capacity along the sublimation curve, the melting-pressure curve, and molar volume in the compressed solid at temperatures from 295 to 764 K and pressures up to 12 GPa. The equation of state is based on the
quasi-harmonic approximation, incorporating a Debye oscillator distribution for the vibrons, two discrete modes for the librons and a further three distinct modes for the internal vibrations of the CO2 molecule. A small anharmonic correction term is included, which is significant mainly in the region of the triple point. The estimated relative uncertainty of molar volume at specified temperature and pressure calculated from the equation of state is 0.02% on the sublimation curve and 1.5% in the compressed solid; for isobaric heat capacity on the sublimation curve, the uncertainty varies from 5.0% to 0.5% between 2 and 195 K. Auxiliary equations for the pressure and molar volume on the sublimation and melting curves are given. The equation of state is valid at temperatures from 0 to 800 K and at pressures from the solid–fluid phase boundary to 12 GPa.
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Wavelengths, Transition Probabilities, and Energy Levels for the Spectra of Cesium (Cs I–Cs LV) J. Phys. Chem. Ref. Data 38, 761 (2009); http://dx.doi.org/10.1063/1.3132702 (163 pages) Online Publication Date: 29 October 2009
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Energy level values, with designations and uncertainties, have been compiled for the spectra of the neutral atom and all positive ions of cesium (Z = 55). Transition wavelengths with classifications, intensities, and transition probabilities are also tabulated. In addition, ground states, ionization energies, and hyperfine structure constants are listed. For most ionization stages experimental data are available; however, for those for which only theoretical calculations or fitted values exist, these are reported. There are a few ionization stages for which only a calculated ionization potential is available.
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Heat Capacity of Liquids: Critical Review and Recommended Values. Supplement II J. Phys. Chem. Ref. Data 39, 013103 (2010); http://dx.doi.org/10.1063/1.3182831 (404 pages) Online Publication Date: 31 March 2010
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A study was carried out in which new experimental data on heat capacities of pure liquid organic and some inorganic compounds were compiled and critically evaluated and recommended values provided. The bulk of the compiled data covers data published in the primary literature between 2000 and 2006 and includes some data published in 2007. However, some data from older sources are also included. The list of compound families covered was extended to include ionic liquids. Parameters of correlating equations for the temperature dependence of heat capacities of liquids were developed. This paper is an update of a two volume monograph entitled Heat Capacity of Liquids: Critical Review and Recommended Values by
Zábranský et al. [J. Phys. Chem. Ref. Data 30, 1199 (2001)]
, which was published in 1996 in the Journal of Physical and Chemical Reference Data as Monograph No. 6, and of Supplement I.
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Fundamental Equations of State for Parahydrogen, Normal Hydrogen, and Orthohydrogen J. Phys. Chem. Ref. Data 38, 721 (2009); http://dx.doi.org/10.1063/1.3160306 (28 pages) Online Publication Date: 4 September 2009
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If the potential for a boom in the global hydrogen economy is realized, there will be an increase in the need for accurate hydrogen thermodynamic property standards. Based on current and anticipated needs, new fundamental equations of state for parahydrogen, normal hydrogen, and orthohydrogen were developed to replace the existing property models. To accurately predict thermophysical properties near the critical region and in liquid states, the quantum law of corresponding states was applied to improve the normal hydrogen and orthohydrogen formulations in the absence of available experimental data. All three equations of state have the same maximum pressure of 2000 MPa and upper temperature limit of 1000 K. Uncertainty estimates in this paper can be considered to be estimates of a combined expanded uncertainty with a coverage factor of 2 for primary data sets. The uncertainty in density is 0.04% in the region between 250 and 450 K and at pressures up to 300 MPa. The uncertainties of vapor pressures and saturated liquid densities vary from 0.1% to 0.2%. Heat capacities are generally estimated to be accurate to within 1%, while speed-of-sound values are accurate to within 0.5% below 100 MPa.
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Compilation of Wavelengths, Energy Levels, and Transition Probabilities for W I and W II J. Phys. Chem. Ref. Data 35, 423 (2006); http://dx.doi.org/10.1063/1.1836763 (261 pages) Online Publication Date: 24 February 2006
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Energy levels, wavelengths, and transition probabilities of the first and second spectra of tungsten, W I and W II, have been compiled. Wavelengths of observed transitions and energy levels derived from those wavelengths have been obtained from a critical evaluation of the available literature. Measured transition probabilities for some of the observed transitions have been compiled from the published literature. © 2006 by the U.S. Secretary of Commerce on behalf of the United States. All rights reserved. |
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Wavelengths, Transition Probabilities, and Energy Levels for the Spectra of Sodium (Na I–Na XI) J. Phys. Chem. Ref. Data 37, 1659 (2008); http://dx.doi.org/10.1063/1.2943652 (105 pages) Online Publication Date: 10 September 2008
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Energy levels, with classifications and uncertainties, have been compiled for the spectra of the neutral atom and all positive ions of sodium (Z = 11). Wavelengths with classifications, intensities, and transition probabilities are also tabulated. In addition, ground states and ionization energies are listed. Where available, the hyperfine structure constants and the percentages of the leading components of the energy levels are included. For all ionization stages of sodium, at least some experimental data are available; however, for those for which only a few transitions have been measured, theoretical calculations or values obtained by isoelectronic fitting are reported. Similarly, theoretical or isoelectronically determined ionization energies are given when they are thought to be more accurate than the available experimental data would produce.
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Evaluated Gas Phase Basicities and Proton Affinities of Molecules: An Update J. Phys. Chem. Ref. Data 27, 413 (1998); http://dx.doi.org/10.1063/1.556018 (244 pages)
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The available data on gas-phase basicities and proton affinities of approximately 1700 molecular, radical and atomic neutral species are evaluated and compiled. Tables of the data are sorted (1) according to empirical formula and (2) according to evaluated gas basicity. This publication constitutes an update of a similar evaluation published in 1984. © 1998 American Institute of Physics and American Chemical Society. |
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IUPAC-NIST Solubility Data Series. 93. Potassium Sulfate in Water J. Phys. Chem. Ref. Data 41, 013103 (2012); http://dx.doi.org/10.1063/1.3679678 (48 pages) Online Publication Date: 8 March 2012
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The solubility data for potassium sulfate in water are reviewed. All data were critically examined for their reliability. The best values were selected on the basis of critical evaluations and presented in tabular form. Fitting equations and plots are also provided. The quantities, units, and symbols used are in accord with IUPAC recommendations. The original data have been reported and, if necessary, transferred into the units and symbols recommended by IUPAC. The literature on solubility data was researched through 2010.
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Gas-Phase Tropospheric Chemistry of Volatile Organic Compounds: 1. Alkanes and Alkenes J. Phys. Chem. Ref. Data 26, 215 (1997); http://dx.doi.org/10.1063/1.556012 (76 pages)
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Literature data (through mid-1996) concerning the gas-phase reactions of alkanes and alkenes (including isoprene and monoterpenes) leading to their first generation products are reviewed and evaluated for tropospheric conditions. The recommendations of the most recent IUPAC evaluation [J. Phys. Chem. Ref. Data, 26, No. 3 (1997)] are used for the ⩽C3 organic compounds, unless more recent data necessitates reevaluation. The most recent review and evaluation of Atkinson [J. Phys. Chem. Ref. Data, Monograph 2, 1 (1994)] concerning the kinetics of the reactions of OH radicals, NO3 radicals, and O3 is also updated for these two classes of volatile organic compounds. © 1997 American Institute of Physics and American Chemical Society. |
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