Leo Brewer

High-Temperature Vaporization Behavior of Oxides II. Oxides of Be, Mg, Ca, Sr, Ba, B, Al, Ga, In, Tl, Si, Ge, Sn, Pb, Zn, Cd, and Hg

In order to assess the high‐temperature vaporization behavior and equilibrium gas phase compositions over the condensed oxides of Be, Mg, Ca, Sr, Ba, B, Al, Ga, In, Tl, Si, Ge, Sn, Pb, Zn, Cd, and Hg, the relevant thermodynamic and molecular constant data have been compiled and critically evaluated. Selected values of the Gibbs energy functions of condensed and vapor phases are given in the form of equations valid over wide temperature ranges, along with the standard entropies and enthalpies of formation. These data were used to generate plots of equilibrium partial pressures of vapor species as functions of temperature for representative environmental conditions ranging from reducing to oxidizing. The calculated partial pressures and compositions agree, for the most part, with experimental results obtained under comparable conditions. Maximum vaporization rates have been calculated using the Hertz–Knudsen equation. Literature references are given.

ENERGIES OF THE ELECTRONIC CONFIGURATIONS OF THE LANTHANIDE AND ACTINIDE NEUTRAL ATOMS.

The thermodynamic data for the lanthanide and actinide metals have been combined with spectroscopic data to develop a method of estimating the energies of the electronic configurations of the neutral gaseous atoms. Energies are tabulated for the lowest spectroscopic level of each configuration. Many of the odd terms of La i have been reclassified.

Energies of the Electronic Configurations of the Singly, Doubly, and Triply Ionized Lanthanides and Actinides

Methods are described for estimating energies of the electronic configurations of the gaseous ions of the lanthanides and actinides. Energies are tabulated for the lowest spectroscopic level of the configurations involving 4f, 5d, 6p, and 6s electrons for the lanthanide ions and 5f, 6d, 7p, and 7s electrons for the actinide ions. Some additional values are listed to be added to the previous tabulation for neutral atoms.

The Stability of Gaseous Diatomic Oxides

The instabilities of FeO, NiO, MnO, and SiO2 upon vaporization, and upper limits to the heats of dissociation of these oxides and SiO have been determined by effusion experiments. The data available in the literature have been treated to obtain the heats of dissociation, or the upper limits thereof, of the gaseous oxides SnO, ZnO, CdO, CuO, PbO, GeO, and TiO.The linear Birge‐Sponer extrapolation of vibrational levels appears to give correct dissociation energies for the fourth‐group oxides.

Ultraviolet Absorption Spectrum of Mercury in Low‐Temperature Matrices

The uv absorptionspectrum of mercury (3 P 1←1 S 0) in Xe, Kr, and Ar matrices has been investigated previously by other workers. The present study verifies the previously published results, extends the investigation to include Ne, N2, and O2 matrices, and analyzes the effects of changing the temperature of the matrix and the concentration of mercury in the matrix. With respect to the gas‐phase transition at 2537 A, in Ne, Ar, Kr, Xe, and N2 the observed absorptions are shifted to shorter wavelength by 940, 1270, 775, 10, and 845 cm−1, respectively. The half‐widths of the absorptions increase with increasing temperature and with increasing mercury concentration. Xe and Kr matrices show partially resolved triplets, while N2 yields a broad doublet. The separate components of the multiplets respond differently upon warming of the matrices. For matrices with a mercury concentration >1%, additional features, presumably due to dimers or other aggregates, are observed.

Uv Absorption Spectrum of Trapped S2

The uv absorption spectrum of trapped S2 has been studied in N2, Ar, Kr, and Xe matrices at 4° and 20°K. Up to 26 vibrational bands of the v″=0 progression of the 3Σu—←3Σg— system were observed. In each of the matrices, the origin of the transition was shifted by an amount characteristic of the particular matrix; red shifts were observed for Xe, Kr, and Ar, while N2 yielded a blue shift. The vibrational spacing indicated distortion of the potential‐energy curve under the influence of the matrix field. The absorption bands were slightly shaded towards the blue and had a half‐width of about 150 cm−1. At low v′, doublet structure was observed. The ir absorption spectrum of the forbidden S2 vibration was also investigated.

Measurement of Lifetimes and Quenching Cross Sections of the B State of I2

The phase‐shift method was used to measure lifetimes of selected vibrational regions from v′=10 to v′∼100, together with self‐quenching collision cross sections, of the B3Π0+u state of I2.The reliability of the method was confirmed by good agreement with other measurements for the lifetime of the mercury 3P1 state. At high optical densities, the observed increase in lifetime was shown to be due to radiation entrapment.Reasonable agreement was found between the lifetime values and absorption measurements, but, contrary to expectations, the self‐quenching cross sections varied only a factor of 1.3 with vibrational excitation whereas the lifetimes varied by as much as a factor of 8.The substantial variation of lifetime with v′, which cannot be merely a wavelength effect, indicates either that spontaneous predissociation of the B state of I2 is an important process which has a rate at least as great as that for radiative decay and which varies considerably with v′ or that the transition moment is changing wit...

Spectrum of C3

The enthalpy of sublimation of C3 as determined by a second law method using both emission and absorption measurements agrees with total vapor pressure and mass spectrometer measurements. The enthalpy agreement and integrated absorption coefficient measurements demonstrate that the so‐called continuum of C3 is a pseudocontinuum and involves the same bound states as the discrete Swings bands of C3(A1Πu↔X1Σ g+). ΔH0°=188±5 kcal/mole for the sublimation of C3 yields an oscillator strength for the 4050 A bands of C3 of 0.13 within a factor of 2.

Ultraviolet Fluorescent and Absorption Spectra of S2 Isolated in Inert‐Gas Matrices

The 3Σu−←3Σg− transition of S2 has been observed in absorption in Ne and in fluorescence in Ne, Ar, Kr, Xe, and N2 matrices. The strongest bands observed in fluorescence belong to the (0, v″) progression as the result of rapid vibrational deexcitation of the 3Σu− state. T00=31 680, 31 350, 30 900, 30 780, and 31 480 cm−1, respectively, for S2 in the five matrices. Unlike the other matrices, argon yields very sharp fluorescent bands, having a width of 15 cm−1. The frequency of the forbidden infrared vibration transition has been calculated from the fluorescent data, and is found to differ from the observed infrared spectrum.

A Thermodynamic and Spectroscopic Study of Gaseous Magnesium Oxide

Vapor pressure measurements on solid magnesium oxide show that the solid vaporizes mainly into molecular species. Spectroscopic experiments have been conducted and have shown that the known gaseous 1Σ electronic state of MgO is not the principal vaporizing species. A study of the ultraviolet bands, produced originally by magnesium burning in air, proves the lower electronic level of the molecule involved in this transition is more important than the 1Σ state of MgO. Within experimental uncertainty the heat of sublimation obtained from vapor pressure measurements agrees with a spectroscopically determined heat of sublimation of the molecule involved in the ultraviolet transition. The ultraviolet bands are shown to originate from a gaseous monomer of MgO. The vapor pressure of MgO at 2200°K is 3.8×10—4 atmos, and the vapor pressure over MgO reaches 1 atmos at 3040±60°K. The D0 value for MgO gas is 4.7 ev.