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Top 20 Most Read Articles
June 2008
The 20 articles with the most full-text downloads during the month, in descending order.
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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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Evaluated Kinetic Data for Combustion Modeling: Supplement II J. Phys. Chem. Ref. Data 34, 757 (2005); http://dx.doi.org/10.1063/1.1748524 (641 pages) Online Publication Date: 27 July 2005
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This compilation updates and expands two previous evaluations of kinetic data on elementary, homogeneous, gas phase reactions of neutral species involved in combustion systems [J. Phys. Chem. Ref Data 21, 411 (1992); 23, 847 (1994)]. The work has been carried out under the auspices of the IUPAC Commission on Chemical Kinetics and the UK Engineering and Physical Sciences Research Council. Individual data sheets are presented for most reactions but the kinetic data for reactions of C2, C, ethyl, i-propyl, t-butyl, and allyl radicals are summarized in tables. Each data sheet sets out relevant thermodynamic data, experimental kinetic data, references, recommended rate parameters with their error limits and a brief discussion of the reasons for their selection. Where appropriate the data are displayed on an Arrhenius diagram or by fall-off curves. Tables summarizing the recommended rate data and the thermodynamic data for the reactant and product species are given, and their sources referenced. As in the previous evaluations the reactions considered relate largely to the combustion in air of organic compounds containing up to three carbon atoms and simple aromatic compounds. Thus the data base has been expanded, largely by dealing with a substantial number of extra reactions within these general areas. © 2005 American Institute of Physics. |
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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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Cross Sections for Electron Collisions with Hydrogen Molecules J. Phys. Chem. Ref. Data 37, 913 (2008); http://dx.doi.org/10.1063/1.2838023 (19 pages) Online Publication Date: 31 March 2008
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Cross section data have been compiled for electron collisions with hydrogen molecules based on 71 references. Cross sections are collected and reviewed for total scattering, elastic scattering, momentum transfer, excitations of rotational, vibrational, and electronic states, dissociation, ionization, emission of radiation, and dissociative attachment. For each process, the recommended values of the cross section are presented for use. The literature has been surveyed through the end of 2006.
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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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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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Atomic Transition Probabilities of Aluminum. A Critical Compilation J. Phys. Chem. Ref. Data 37, 709 (2008); http://dx.doi.org/10.1063/1.2734564 (203 pages) Online Publication Date: 6 March 2008
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This compilation is the second in a series of updates to Atomic Transition Probabilities, Sodium through Calcium, published in 1969 by
Wiese et al. [Atomic Transition Probabilities, Vol. II, Vol. II: Sodium through Calcium, NSROS-NBS Vol. 2 (U.S. GPO, Washington, D.C., 1969)]
. Atomic transition probabilities have been critically evaluated and compiled for about 5000 spectral lines of aluminum (nuclear charge Z = 13). The cited values and their estimated uncertainties are based on our consideration of all available theoretical and experimental literature sources. All ionization stages (except for hydrogenic) are covered, and the data are presented in separate tables for each atom and ion. Separate listings are given for “allowed” (electric dipole) and “forbidden” (magnetic dipole plus electric and magnetic quadrupole) transitions. In each spectrum, lines are grouped into multiplets which are arranged in order of ascending lower- and upper-level energies, respectively. For each line, the emission transition probability Aki, the line strength S, and (for allowed lines) the absorption oscillator strength fik are given, together with the spectroscopic designation, the wavelength, the statistical weights, and the energy levels of the lower and upper states. The estimated relative uncertainties of the line strength are also indicated, as are the source citations. We include only those lines whose transition rates are deemed sufficiently accurate to qualify as reference values. Short introductions precede the tables for each ion.
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J. Phys. Chem. Ref. Data 29, 331 (2000); http://dx.doi.org/10.1063/1.1285884 (55 pages)
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A thermodynamic property formulation for standard dry air based upon available experimental p–ρ–T, heat capacity, speed of sound, and vapor–liquid equilibrium data is presented. This formulation is valid for liquid, vapor, and supercritical air at temperatures from the solidification point on the bubble-point curve (59.75 K) to 2000 K at pressures up to 2000 MPa. In the absence of reliable experimental data for air above 873 K and 70 MPa, air properties were predicted from nitrogen data in this region. These values were included in the determination of the formulation to extend the range of validity. Experimental shock tube measurements on air give an indication of the extrapolation behavior of the equation of state up to temperatures and pressures of 5000 K and 28 GPa. The available measurements of thermodynamic properties of air are summarized and analyzed. Separate ancillary equations for the calculation of dew and bubble-point pressures and densities of air are presented. In the range from the solidification point to 873 K at pressures to 70 MPa, the estimated uncertainty of density values calculated with the equation of state is 0.1%. The estimated uncertainty of calculated speed of sound values is 0.2% and that for calculated heat capacities is 1%. At temperatures above 873 K and 70 MPa, the estimated uncertainty of calculated density values is 0.5% increasing to 1.0% at 2000 K and 2000 MPa. In addition to the equation of state for standard air, a mixture model explicit in Helmholtz energy has been developed which is capable of calculating the thermodynamic properties of mixtures containing nitrogen, argon, and oxygen. This model is valid for temperatures from the solidification point on the bubble-point curve to 1000 K at pressures up to 100 MPa over all compositions. The Helmholtz energy of the mixture is the sum of the ideal gas contribution, the real gas contribution, and the contribution from mixing. The contribution from mixing is given by a single generalized equation which is applied to all mixtures used in this work. The independent variables are the reduced density and reduced temperature. The model may be used to calculate the thermodynamic properties of mixtures at various compositions including dew and bubble-point properties and critical points. It incorporates the most accurate published equation of state for each pure fluid. The mixture model may be used to calculate the properties of mixtures generally within the experimental accuracies of the available measured properties. The estimated uncertainty of calculated properties is 0.1% in density, 0.2% in the speed of sound, and 1% in heat capacities. Calculated dew and bubble-point pressures are generally accurate to within 1%. © 2000 American Institute of Physics and American Chemical Society. |
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J. Phys. Chem. Ref. Data 35, 1331 (2006); http://dx.doi.org/10.1063/1.2201308 (34 pages) Online Publication Date: 8 August 2006
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Reference tables of second pVT-virial coefficients B(T), viscosity η(T), and self-diffusion ρD(T) are given for all neat alkanes CnH2n+2, n<6, for temperatures T ⩽ 1200 K starting at 100 K for CH4, 150 K for C2H6, and 180 K for C3H8, n-C4H10, i-C4H10, n-C5H12, i-C5H12, and C(CH3)4. Restricting ourselves to low densities the thermophysical properties are calculated by means of an isotropic (n-6) Lennard-Jones temperature dependent potential (LJTDP). In this model the potential well depth εeff(T) and the separation at minimum energy Rm(eff)(T) are explicitly temperature dependent, whereas the repulsive term n>12 is independent of T. The LJTDP has been used before in order to construct reference tables of thermophysical properties of neat gases [
Zarkova and Hohm, J. Phys. Chem. Ref. Data 31, 183 (2002)
] and binary mixtures [
Zarkova, Hohm, and Damyanova, J. Phys. Chem. Ref. Data 32, 1591 (2003)
]. However, those studies were restricted to atoms and globularly shaped nondipolar molecules. Here the approach is extended to elongated, not necessarily spherically symmetric, and in part slightly dipolar molecules. As in previous works the potential parameters ε(eff)(T), Rm(eff)(T), and n are determined by minimizing the root-mean-square deviation between calculated and experimentally obtained thermophysical properties B(T), η(T), ρD(T), and the second acoustic virial coefficient β(T) normalized to their experimental error. In extension of our previous efforts we present a thorough statistical analysis of the experimental input data which gives us the possibility to select primary data which could be used to build up a database.
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J. Phys. Chem. Ref. Data 37, 933 (2008); http://dx.doi.org/10.1063/1.2804088 (186 pages) Online Publication Date: 8 May 2008
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This paper is the fourth and final volume in the halate solubility series. The solubility data for halates of transition metals, lanthanides, actinides, ammonium, and metallic elements of the main groups 12–14 are reviewed. Where appropriate, binary, ternary, and multicomponent systems are critically evaluated. Most of the solubility results were obtained in water or aqueous solutions of electrolytes. The solubility in organic solvents and aqueous-organic solvent mixtures is also collected in this volume. All these 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 graphical plots are also provided. When numerical data were not reported in an original publication, they were read out from figures and digitized by the compilers. The quantities, units, and symbols used in this volume are in accord with IUPAC recommendations. We always reported the original data and, if necessary, transferred them into the IUPAC recommended units and symbols. The literature on the solubility data was researched through 2002. The halates of these metals play a role in industrial processes. For example, some halates are essential as catalysts, heat stabilizers, and blanching reagents for manufacturing polymer products such as textiles and resins. Some iodates are used in pyrotechnic compounds for weather modification and colored smoke generation. The nonlinear halate crystals are important in construction of optical devices.
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J. Phys. Chem. Ref. Data 33, 1005 (2004); http://dx.doi.org/10.1063/1.1691451 (7 pages) Online Publication Date: 28 October 2004
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A simple extended corresponding-states principle is used to represent the vapor pressure of ammonia and trideuteroammonia from the triple point to critical point and to describe the available experimental data along with extrapolation beyond their ranges of available experimental data. This work takes advantage of the adoption of the ITS-90 temperature scale and of the new critical parameters obtained from the extended corresponding-states principle. The vapor pressure data are described within their scatter in the entire temperature range. Comparisons with the available data show that the extended corresponding-states principle may calculate the vapor-pressure values within 0.05%–0.1% The substance-dependent characteristic parameters are given, such as critical temperature, critical density, critical pressure, acentric factor, and aspherical factor. The values of the pressures, along with their first and second derivatives as a function of temperature over the entire region from the triple point to the critical point are tabulated and recommended for scientific and practical uses. © 2004 American Institute of Physics. |
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Microwave Spectra of Molecules of Astrophysical Interest. XXVI. Acetic Acid (CH3COOH) J. Phys. Chem. Ref. Data 37, 97 (2008); http://dx.doi.org/10.1063/1.2815328 (169 pages) Online Publication Date: 19 February 2008
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The microwave spectrum of acetic acid is critically reviewed and supplemented with spectral frequency calculations derived from the rotation-torsion analysis. A simultaneous analysis of the torsional ground state, vt = 0, and first and second torsionally excited states, vt = 1 and 2, was carried out using the so-called “rho axis method.” The primary objective of this review is to provide radio astronomers with complete spectral coverage over the 1–400 GHz range for the ground and vt = 1 states, covering rotational quantum numbers J ⩽ 30 and ∣Ka∣ ⩽ 15.
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IUPAC Critical Evaluation of Thermochemical Properties of Selected Radicals. Part I J. Phys. Chem. Ref. Data 34, 573 (2005); http://dx.doi.org/10.1063/1.1724828 (84 pages) Online Publication Date: 27 May 2005
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This is the first part of a series of articles reporting critically evaluated thermochemical properties of selected free radicals. The present article contains datasheets for 11 radicals: CH, CH2(triplet), CH2(singlet), CH3, CH2OH, CH3O, CH3CO, C2H5O, C6H5CH2, OH, and NH2. The thermochemical properties discussed are the enthalpy of formation, as well as the heat capacity, integrated heat capacity, and entropy of the radicals. One distinguishing feature of the present evaluation is the systematic utilization of available kinetic, spectroscopic and ion thermochemical data as well as high-level theoretical results. © 2005 American Institute of Physics. |
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J. Phys. Chem. Ref. Data 29, 1361 (2000); http://dx.doi.org/10.1063/1.1349047 (73 pages)
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A new formulation for the thermodynamic properties of nitrogen has been developed. Many new data sets have become available, including high accuracy data from single and dual-sinker apparatuses which improve the accuracy of the representation of the pρT surface of gaseous, liquid, and supercritical nitrogen, including the saturation states. New measurements of the speed of sound from spherical resonators yield accurate information on caloric properties in gaseous and supercritical nitrogen. Isochoric heat capacity and enthalpy data have also been published. Sophisticated procedures for the optimization of the mathematical structure of equations of state and special functional forms for an improved representation of data in the critical region were used. Constraints regarding the structure of the equation ensure reasonable results up to extreme conditions of temperature and pressure. For calibration applications, the new reference equation is supplemented by a simple but also accurate formulation, valid only for supercritical nitrogen between 250 and 350 K at pressures up to 30 MPa. The uncertainty in density of the new reference equation of state ranges from 0.02% at pressures less than 30 MPa up to 0.6% at very high pressures, except in the range from 270 to 350 K at pressures less than 12 MPa where the uncertainty in density is 0.01%. The equation is valid from the triple point temperature to temperatures of 1000 K and up to pressures of 2200 MPa. From 1000 to 1800 K, the equation was validated with data of limited accuracy. The extrapolation behavior beyond 1800 K is reasonable up to the limits of chemical stability of nitrogen, as indicated by comparison to experimental shock tube data. © 2001 by the U.S. Secretary of Commerce on behalf of the United States. All rights reserved. |
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J. Phys. Chem. Ref. Data 37, 1119 (2008); http://dx.doi.org/10.1063/1.2838022 (28 pages) Online Publication Date: 9 May 2008
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The mutual solubilities and related liquid-liquid equilibria of C2–C5 ethers with water are exhaustively and critically reviewed. Reports of experimental determination of solubility in ten chemically distinct binary systems that appeared in the primary literature prior to the end of 2006 are compiled. For three systems, sufficient data are available to allow critical evaluation. All data are expressed as mass percent and mole fraction as well as the originally reported units. In addition to the standard evaluation criteria used throughout the Solubility Data Series, a recently developed method based on the evaluation of all experimental data for a given series of ethers was used.
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Vibrational and Electronic Energy Levels of Polyatomic Transient Molecules. Supplement B J. Phys. Chem. Ref. Data 32, 1 (2003); http://dx.doi.org/10.1063/1.1497629 (441 pages) Online Publication Date: 18 February 2003
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A summary is presented of recently published, critically evaluated experimental vibrational and electronic energy level data for approximately 1700 neutral and ionic transient molecules and high temperature species possessing from three to sixteen atoms. Although the emphasis is on species with lifetimes too short for study using conventional sampling techniques, there has been selective extension of the compilation to include data for isolated molecules of inorganic species such as the heavy-metal oxides, which are important in a wide variety of industrial chemical systems. Radiative lifetimes and the principal rotational constants are included. Observations in the gas phase, in molecular beams, and in rare-gas and diatomic molecule matrices are evaluated, and several thousand references are cited. The types of measurement surveyed include conventional and laser-based absorption and emission techniques, laser absorption with mass analysis, and photoelectron spectroscopy. © 2003 by the U.S. Secretary of Commerce on behalf of the United States. All rights reserved. |
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Wavelengths, Energy Level Classifications, and Energy Levels for the Spectrum of Neutral Neon J. Phys. Chem. Ref. Data 33, 1113 (2004); http://dx.doi.org/10.1063/1.1797771 (46 pages) Online Publication Date: 24 January 2005
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We have prepared a comprehensive critically evaluated compilation of the most accurate wavelength measurements for classified lines of neutral neon (Ne I) in its natural isotopic abundance. Data from 19 sources spanning the region 256 Å to 54 931 Å are included. Based on this line list we have derived optimized values for the energy levels of neutral neon. Tabular data for 1595 classified lines and 374 energy levels are provided. In addition to the observed wavelengths, we present revised wavelengths calculated from the optimized energy levels for all lines that have been previously recommended for use as secondary wavelength standards. © 2005 by the U.S. Secretary of Commerce on behalf of the United States. All rights reserved. |
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J. Phys. Chem. Ref. Data 37, 1183 (2008); http://dx.doi.org/10.1063/1.2904462 (1 page) Online Publication Date: 22 May 2008
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Heat Capacity of Liquids: Critical Review and Recommended Values. Supplement I J. Phys. Chem. Ref. Data 30, 1199 (2001); http://dx.doi.org/10.1063/1.1407866 (491 pages)
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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, critically evaluated, and recommended values provided. Compounds included in the compilation have a melting point below 573 K. The bulk of the compiled data covers data published in the primary literature between 1993 and 1999 and some data of 2000. However, some data from older sources were also included. The data were taken from almost 1030 literature references. Parameters of correlating equations for 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 (96ZAB/RUZ) that was published in 1996 in the Journal of Physical and Chemical Reference Data as Monograph No. 6 and was the product of the IUPAC Project No. 121/11/87. © 2002 by the U.S. Secretary of Commerce on behalf of the United States. All rights reserved. |
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Wavelengths, Energy Level Classifications, and Energy Levels for the Spectrum of Neutral Mercury J. Phys. Chem. Ref. Data 35, 1519 (2006); http://dx.doi.org/10.1063/1.2204960 (30 pages) Online Publication Date: 11 October 2006
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A comprehensive critically evaluated compilation of the most accurate wavelength measurements for classified lines of neutral mercury (Hg I) for both the single isotope
 and for mercury in its natural isotopic abundance has been prepared. Data from 12 sources spanning the region from 1849 to 40 050 Å are included for . Data from 39 sources spanning the region from 745 to 64 918 Å are included for the natural isotope mixture. Based on these line lists we have derived optimized values for the energy levels of neutral mercury for both and the natural isotopic mixture. Tabular data for 105 classified lines and 60 energy levels are provided for and 658 lines and 275 energy levels are provided for the natural isotopic mixture. |
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