Dissociation Energy of NaO(g) and the Heat of Atomization of Na2O(g)
01 Nov 1970-Journal of Chemical Physics (American Institute of Physics)-Vol. 53, Iss: 9, pp 3403-3408
TL;DR: In this paper, the vaporization of Na2O(c) has been studied mass spectrometrically and it was found that the vaporisation yields primarily Na(g) and O2(g).
Abstract: The vaporization of Na2O(c) has been studied mass spectrometrically. It was found that the vaporization yields primarily Na(g) and O2(g), with NaO(g) and Na2O(g) being minor vapor constituents. From equilibria involving Na2O(c), Na2O(g), Na(g), NaO(g), and O2(g), it was possible to measure ΔHf298°[NaO(g)] = 24.3 ± 4 kcal/mol and ΔHf298°[Na2O(g)] = − 9.9 ± 3 kcal/mol. These values yield D0°(NaO) = 60.3 ± 4 kcal/mole (2.61 ± 0.20 eV) and D0°(Na2O) = 119.8 ± 3 kcal/mol (5.20 ± 0.15 eV). The appearance potentials of NaO+ and Na2O+ were measured and found to be 6.5 ± 0.7 and 5.5 ± 0.5 eV, respectively. These appearance potentials are suggested to be close to the true ionization potentials of the molecules. Implications of these results regarding some recent beam experiments are briefly discussed.
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01 Oct 1993
TL;DR: In this article, a library of thermodynamic data and transport properties are given for individual species in the form of least-squares coefficients for 1130 solid, liquid, and gaseous species.
Abstract: Libraries of thermodynamic data and transport properties are given for individual species in the form of least-squares coefficients. Values of C(sup 0)(sub p)(T), H(sup 0)(T), and S(sup 0)(T) are available for 1130 solid, liquid, and gaseous species. Viscosity and thermal conductivity data are given for 155 gases. The original C(sup 0)(sub p)(T) values were fit to a fourth-order polynomial with integration constants for H(sup 0)(T) and S(sup 0)(T). For each species the integration constant for H(sup 0)(T) includes the heat of formation. Transport properties have a different functional form. The temperature range for most of the data is 300 to 5000 K, although some of the newer thermodynamic data have a range of 200 to 6000 K. Because the species are mainly possible products of reaction, the data are useful for chemical equilibrium and kinetics computer codes. Much of the data has been distributed for several years with the NASA Lewis equilibrium program CET89. The thermodynamic properties of the reference elements were updated along with about 175 species that involve the elements carbon, hydrogen, oxygen, and nitrogen. These sets of data will be distributed with the NASA Lewis personal computer program for calculating chemical equilibria, CETPC.
715 citations
TL;DR: In this article, the authors describe a laboratory study into the chemical pathways by which Na + is converted to Na in the upper atmosphere, showing that the lifetime of Na+ changes very rapidly from more than a day above 100 km to just a few minutes at 90 km.
Abstract: This paper describes a laboratory study into the chemical pathways by which Na + is converted to Na in the upper atmosphere. The termolecular clustering reactions of Na + with N 2 , O 2 , and CO 2 were studied in a low-temperature fast flow reactor coupled to a quadrupole mass spectrometer. This yielded κ(Na + + N 2 + He, 93-255 K) = (1.20 ± 0.13) x 10 -30 (T/200 K) -(2.20±0.09) , κ(Na + + O 2 + He, 93-130 K) = (5.20 ± 2.62) x 10-31 (T/200 K) -(2.64±0.74) κ(Na + + CO 2 + He, 158-300 K) = (9.05±1.38) x 10 -30 (T/200 K) -(2.84±0.48) , where the units are cm 6 molecule -2 s -1 and the stated errors are a combination of the 2σ standard errors in the kinetic data and the systematic errors in the temperature, pressure, and flow rates. It was then shown that atomic O will ligand switch with Na.N 2 + but not with Na.CO 2 + , and that the former reaction proceeds essentially at the Langevin collision frequency. The neutralization of Na + in the upper atmosphere is therefore rather complex. The first step is formation of the Na.N 2 + ion from the recombination of Na + with N 2 . This cluster ion can then either switch with CO 2 , which leads to a stable cluster ion that will undergo dissociative electron recombination to form Na; or switch with atomic O, which reforms Na + . The result of this is that the lifetime of Na + changes very rapidly from more than a day above 100 km to just a few minutes at 90 km. Furthermore, the rate of neutralization is largely independent of the electron concentration. A simple model describing the conversion of Na + to atomic Na in a descending sporadic E layer demonstrates that this ion-molecule mechanism appears to fulfil many of the major criteria for producing sporadic sodium layers.
145 citations
TL;DR: In this article, a tin sulfide-carbon (SnS-C) nanocomposite is prepared by a simple high-energy mechanical milling method, which is composed of well crystallized SnS nanoparticles with a size of about 15 nm, which are dispersed uniformly in the conductive carbon matrix.
Abstract: A tin(II) sulfide–carbon (SnS–C) nanocomposite is prepared by a simple high-energy mechanical milling method. XRD, SEM and TEM characterizations show that the nanocomposite is composed of well crystallized SnS nanoparticles with a size of about 15 nm, which are dispersed uniformly in the conductive carbon matrix. The SnS–C electrode exhibits a high Na storage capacity (568 mA h g−1 at 20 mA g−1) and excellent cycling stability (97.8% capacity retention over 80 cycles) as well as high-rate capability. Ex situ XRD result confirms a sequential conversion and alloying–dealloying reaction mechanism of the SnS–C electrode during the Na uptaking and extraction cycles. The superior electrochemical performance of the electrodes can be attributed to the small crystalline size of SnS and good carbon coating, which facilitate electrochemical utilization and maintain the structural integrity.
133 citations
TL;DR: Expose de la technique qui peut servir a stimuler les applications analytiques de la phosphorescence a temperature ambiante as discussed by the authors, i.e., a technique that peut stimuler a stimulator les applications analysetiques of the phosphorescence.
Abstract: Expose de la technique qui peut servir a stimuler les applications analytiques de la phosphorescence a temperature ambiante
132 citations
TL;DR: In this paper, it is shown that NaO2 can severely perturb the NaOH/Na ratio and produce significant concentration overshoots over that predicted from the balance of the reaction of Na with H2O.
Abstract: Results are presented which, it is claimed, lead to a correction of previous misconceptions over the relative importance and kinetics of NaO2. It is shown that its rapid conversion to NaO and NaOH is such that it can severely perturb the NaOH/Na ratio and produce significant concentration overshoots over that predicted from the balance of the reaction of Na with H2O. This becomes increasingly the case in flames of large O2 concentrations and temperatures below 2500 K; and the corresponding large rate constants for the termolecular formation of the other alkali peroxides imply that similar considerations will be necessary for them. Depending on the rate constants for the exothermic conversions of MO2 to MO or MOH, the steady-state concentrations of MO2 could be more or less significant than for sodium. Owing to numerous reactions that produce these conversions, the MOH species will probably be the dominant species in all cases in oxygen-rich hydrogen or hydrocarbon flames, with MO concentrations at not greater than 1 percent of the bound metal.
115 citations
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TL;DR: In this paper, a new method was devised for obtaining absolute cross sections of gases relative to H2, and a McLeod gauge was used to obtain the absolute cross section in H2.
Abstract: The total ionization cross sections of He, Ne, Ar, Kr, Xe, H2, D2, N2, O2, CO, NO, CO2, N2O, and CH4 have been measured from threshold to 1000 eV in a total ionization tube. More limited measurements were performed in C2H4 and SF6. Great care was taken to assure complete collection of electron and ion currents, and the absence of spurious instrumental errors. A new method was devised for obtaining absolute cross sections of gases relative to H2, and a McLeod gauge was used to obtain the absolute cross section in H2. The cross sections in NO and O2 could not be obtained by this method, and an approximate correction to direct McLeod‐gauge readings was used for these gases. It is believed that the results are as accurate as is possible with the present method. It is difficult to explain the differences found between cross sections measured by various investigators. McLeod‐gauge errors appear to account for most of the difference in absolute magnitude.
1,758 citations
TL;DR: In this article, a detailed discussion of the methods of calculating atomic polarizabilities and shielding factors and the relationships between them are demonstrated, and a more accurate procedure, the coupled Hartree-Fock approximation, is described.
Abstract: A detailed discussion is given of the methods of calculating atomic polarizabilities and shielding factors and the relationships between them are demonstrated. The formulation of the uncoupled Hartree-Fock approximation is presented and it is shown that the methods are all approximate versions of it. A more accurate procedure, the coupled Hartree-Fock approximation, is described. Comprehensive tables of dipole and quadrupole polarizabilities and of quadrupole shielding factors are included together with an assessment of the probable accuracy.
646 citations