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Top 20 Most Read Articles
August 2009
The 20 articles with the most full-text downloads during the month, in descending order.
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Accurate Atomic Transition Probabilities for Hydrogen, Helium, and Lithium J. Phys. Chem. Ref. Data 38, 565 (2009); http://dx.doi.org/10.1063/1.3077727 (156 pages) Online Publication Date: 24 June 2009
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We have carried out a comprehensive tabulation of the atomic transition probabilities for allowed and forbidden lines of hydrogen, helium and lithium, including Li II, as well as the hydrogen isotopes deuterium and tritium. Altogether, we tabulated about 3600 transitions and listed scaling relations for the hydrogenlike ions He II and Li III. The selected data are based on a critical evaluation of available literature sources and are all taken from recent advanced calculations. The tables are normally arranged in multiplets, and these are ordered in increasing excitation energies. For hydrogen, deuterium, and tritium, the energy levels are degenerate, i.e., all energy levels of the same principal quantum number essentially coincide. Thus, the principal tables for these species are for the average transition probabilities of lines between different principal quantum numbers.
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A Fundamental Equation of State for 2-propanol (C3H8O) in the Extended Equation of State Format J. Phys. Chem. Ref. Data 38, 127 (2009); http://dx.doi.org/10.1063/1.3112608 (44 pages) Online Publication Date: 13 May 2009
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An innovative method for the regression of a fundamental equation of state of a pure fluid was recently proposed. This technique, called an extended equation of state, adopts a framework similar to the extended corresponding states method but uses a cubic equation for the target fluid instead of the equation of state for the reference fluid, and shape functions are expressed through a multilayer feedforward neural network. The use of a neural network assures very high flexibility of the functional forms to be regressed, allowing the resulting model to represent the thermodynamic properties of a pure fluid with an accuracy comparable to that attained by state-of-the-art multiparameter equations of state. The technique is applied here to 2-propanol to derive a dedicated equation of state in a heuristic mode directly from the available experimental data. The majority of the data cover the range of temperatures from 280 to 600 K and pressures up to 50 MPa; this is also the validity range of the developed equation. For the present case, primarily due to the unfavorable situation of the data, all of the available thermodynamic properties have been used for the regression procedure in order to get the expected accuracy. The model has been validated with data for coexistence states, density, isobaric and isochoric heat capacities, and speed of sound. The obtained results are satisfactory because the proposed equation of state represents the available data within their mean experimental uncertainties.
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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 36, 1 (2007); http://dx.doi.org/10.1063/1.2360986 (18 pages) Online Publication Date: 8 February 2007
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All the currently available experimental permittivity data for pure water are used to derive an interpolation function that precisely represents ε(ν,t,) at standard atmospheric pressure, for frequencies and temperatures in the ranges 0 ⩽ ν ⩽ 25 THz and 0 ⩽ t ⩽ 100 °C. The permittivity data is represented in terms of relaxations and resonances processes. There are three relaxations in the microwave region and two resonances in the far infrared. The temperature dependence of the relaxation and resonance parameters are determined. For example, at 25 °C the three relaxation frequencies are 18.56 GHz, 167.83 GHz, 1.944 THz and the two resonance frequencies are 4.03 and 14.48 THz.
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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 37, 1997 (2008); http://dx.doi.org/10.1063/1.3005673 (12 pages) Online Publication Date: 14 November 2008
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Polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) are of global concern due to their persistence, their tendency to bioaccumulate, and their extremely high toxicity. The fate of the PCDD/Fs in the environment is largely determined by their physical-chemical properties, such as solubility in water (SW, mol m−3), solubility in octanol (SO, mol m−3), and vapor pressure (P, Pa). It is not unusual that the range of reported values for a given property varies over several orders of magnitude, especially for the highly chlorinated congeners, and consequently, it is a challenge to select physical-chemical property data from the literature for use in chemical fate and risk assessments. In the current study, physical-chemical property data [P, SW, SO, Henry’s law constant (H), partitioning coefficients between octanol-water (KOW) and octanol-air (KOA)] for 15 DDs and 17 DFs at 293–299 K are compiled from the literature and evaluated to select literature derived values that are then adjusted to conform to thermodynamic constraints using a least-squares adjustment procedure. We also present an analysis of available data on internal energies of phase change (ΔUA, ΔUW, ΔUO, ΔUOW, ΔUAW, ΔUOA) at 298 K, which describe the temperature dependence of the partitioning properties. The final adjusted values (FAVs) derived from this study are recommended as physical-chemical property data for PCDD/Fs for use in environmental fate modeling. The FAVs for internal energies of phase change can be used as a first approximation for estimating properties at temperatures other than 298 K.
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Cross Sections for Electron Collisions with Oxygen Molecules J. Phys. Chem. Ref. Data 38, 1 (2009); http://dx.doi.org/10.1063/1.3025886 (20 pages) Online Publication Date: 12 December 2008
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Cross section data are collected and reviewed for electron collisions with oxygen molecules. Included are the cross sections for total and elastic scatterings, momentum transfer, excitations of rotational, vibrational, and electronic states, dissociation, ionization, electron attachment, and emission of radiations. For each process, the recommended values of the cross sections are presented, when possible. The literature has been surveyed through the end of 2007.
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New International Formulation for the Viscosity of H2O J. Phys. Chem. Ref. Data 38, 101 (2009); http://dx.doi.org/10.1063/1.3088050 (25 pages) Online Publication Date: 21 April 2009
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The International Association for the Properties of Water and Steam (IAPWS) encouraged an extensive research effort to update the IAPS Formulation 1985 for the Viscosity of Ordinary Water Substance, leading to the adoption of a Release on the IAPWS Formulation 2008 for the Viscosity of Ordinary Water Substance. This manuscript describes the development and evaluation of the 2008 formulation, which provides a correlating equation for the viscosity of water for fluid states up to 1173 K and 1000 MPa with uncertainties from less than 1% to 7% depending on the state point.
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Critically Evaluated Thermochemical Properties of Polycyclic Aromatic Hydrocarbons J. Phys. Chem. Ref. Data 37, 1855 (2008); http://dx.doi.org/10.1063/1.2955570 (142 pages) Online Publication Date: 23 October 2008
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Experimental thermochemical properties of benzene, toluene, and 63 polycyclic aromatic hydrocarbons, published within the period 1878–2008 (over 350 references), are reported. Available experimental data for the enthalpies of combustion used to calculate enthalpies of formation in the condensed state, combined with sublimation, vaporization, and fusion enthalpies, are critically evaluated. Whenever possible, recommended values for these thermochemical properties and for the enthalpies of formation in the gas state at T = 298.15 K are provided.
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Announcement: Multimedia Capability Added to Journal of Physical and Chemical Reference Data J. Phys. Chem. Ref. Data 38, 97 (2009); http://dx.doi.org/10.1063/1.3099311 (1 page) Online Publication Date: 10 March 2009
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CODATA recommended values of the fundamental physical constants: 2006 J. Phys. Chem. Ref. Data 37, 1187 (2008); http://dx.doi.org/10.1063/1.2844785 (98 pages) Online Publication Date: 15 July 2008
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This paper gives the 2006 self-consistent set of values of the basic constants and conversion factors of physics and chemistry recommended by the Committee on Data for Science and Technology (CODATA) for international use. Further, it describes in detail the adjustment of the values of the constants, including the selection of the final set of input data based on the results of least-squares analyses. The 2006 adjustment takes into account the data considered in the 2002 adjustment as well as the data that became available between 31 December 2002, the closing date of that adjustment, and 31 December 2006, the closing date of the new adjustment. The new data have led to a significant reduction in the uncertainties of many recommended values. The 2006 set replaces the previously recommended 2002 CODATA set and may also be found on the World Wide Web at physics.nist.gov/constants.
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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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Binding Energies in Atomic Negative Ions: III J. Phys. Chem. Ref. Data 28, 1511 (1999); http://dx.doi.org/10.1063/1.556047 (23 pages)
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This article updates a 14 yr old review on this subject [J. Phys. Chem. Ref. Data 14, 731 (1985)]. A survey of the electron affinity determinations for the elements up to Z = 94 is presented, and based upon these data, a set of recommended electron affinities is established. New developments in the experimental methods which yield accurate electron binding energies are described. Fine structure splittings and excited state energies of negative ions as well as lifetimes of metastable states are given. Progress in theoretical calculations of atomic electron affinities is documented by comparison with reliable experimental data. © 1999 American Institute of Physics and American Chemical Society. |
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Announcement: Chinese, Japanese, and Korean Characters Available for Author Names J. Phys. Chem. Ref. Data 38, 99 (2009); http://dx.doi.org/10.1063/1.3110164 (1 page) Online Publication Date: 19 March 2009
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Measurement Analysis of Glass Transition Temperature for Sucrose and Trehalose Aqueous Solutions J. Phys. Chem. Ref. Data 36, 1279 (2007); http://dx.doi.org/10.1063/1.2779330 (7 pages) Online Publication Date: 21 September 2007
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Glass transition temperatures (Tg) for sucrose, trehalose, and water have been determined by numerous studies in the past. Literature values appear to be fairly scattered and compromise the applicability of the Gordon–Taylor equation for aqueous solutions. This work deals with the effect of the sample history and heating process on the Tg values. Consistent estimates for the glass transition temperature of both disaccharides in aqueous solution can be made from these observations.
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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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Cross Sections for Electron Collisions with Water Molecules J. Phys. Chem. Ref. Data 34, 1 (2005); http://dx.doi.org/10.1063/1.1799251 (22 pages) Online Publication Date: 14 February 2005
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Cross section data have been compiled from the literature (to the end of 2003) for electron collisions with water (H2O) molecules. All major collision processes are reviewed including: total scattering, elastic scattering, momentum transfer, excitation of rotational, vibrational, and electronic states, ionization, electron attachment, dissociation, and emission of radiation. In each case we assess the collected data and provide a recommendation of the values of the cross section to be used. They are presented in a tabular form. Isotope effects (H2O versus D2O) are discussed as far as information is available. © 2005 American Institute of Physics. |
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J. Phys. Chem. Ref. Data 37, 1765 (2008); http://dx.doi.org/10.1063/1.2956740 (89 pages) Online Publication Date: 15 October 2008
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This volume presents solubility data for rare earth metal chlorides in water and in ternary and quaternary aqueous systems. The material is divided into three parts: scandium group (Sc, Y, La), light lanthanide (Ce-Eu), and heavy lanthanide (Gd-Lu) chlorides; this part covers the scandium group. Compilations of all available experimental data are introduced for each rare earth metal chloride with a corresponding critical evaluation. Every such evaluation contains a tabulated collection of all solubility results in water, a scheme of the water-rich part of the equilibrium (Y, La, Ln)Cl3–H2O phase diagram, solubility equation(s), a selection of suggested solubility data, and a discussion of the multicomponent systems. Because the ternary and quaternary systems were almost never studied more than once, no critical evaluations or systematic comparisons of such data were possible. Only simple chlorides (no complexes) are treated as the input substances in this work. The literature (including a thorough coverage of papers in Chinese and Russian) has been covered through the middle of 2007.
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Handbook of Basic Atomic Spectroscopic Data J. Phys. Chem. Ref. Data 34, 1559 (2005); http://dx.doi.org/10.1063/1.1800011 (701 pages) Online Publication Date: 28 September 2005
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© 2005 American Institute of Physics. |
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Experimental Vibrational Zero-Point Energies: Diatomic Molecules J. Phys. Chem. Ref. Data 36, 389 (2007); http://dx.doi.org/10.1063/1.2436891 (9 pages) Online Publication Date: 18 April 2007
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Vibrational zero-point energies (ZPEs), as determined from published spectroscopic constants, are derived for 85 diatomic molecules. Standard uncertainties are also provided, including estimated contributions from bias as well as the statistical uncertainties propagated from those reported in the spectroscopy literature. This compilation will be helpful for validating theoretical procedures for predicting ZPEs, which is a necessary step in the ab initio prediction of molecular energetics.
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