bluuebunny/crossref_metadata_2025 huggingface dataset:
Vibrational Spectra of Fluorinated Aromatics. VII. 1,2,4-Trifluorobenzene
Authors: Ferguson E. E. , Hudson R. L. , Nielsen J. Rud , Smith D. C.
Published: January 2005

The infrared absorption spectrum of liquid 1,2,4-trifluorobenzene has been obtained in the region 2–38μ with the aid of LiF, NaCl, KBr, and KRS−5 prisms. The Raman spectrum of the liquidh as been photographed with a three-prism glass spectrograph of linear dispersion 15A/mm at 4358A, and depolarization ratios have been measured for the stronger Raman bands. A complete assignment of fundamental vibration frequencies is given, and the spectra are interpreted in detail.
Vibrational Spectra of Fluorinated Aromatics. VIII. 1,4-Bis(trifluoromethyl)benzene
Authors: Ferguson E. E. , Mikkelsen Louis , Nielsen J. Rud , Smith D. C.
Published: January 2005

The infrared absorption of liquid 1,4-bis(trifluoromethyl) benzene has been obtained in the region 2–22μ with the aid of LiF, NaCl, and KBr prisms. The Raman spectrum has been photographed with a three-prism glass spectrograph of linear dispersion 15A/mm at 4358A. A nearly complete assignment of fundamental vibration frequencies is given, and the spectra are interpreted in detail.
X-Ray Scattering from a ``Free-Volume'' Liquid
Authors: Lund Louis H.
Published: January 2005

The x-ray scattering of a monatomic liquid is calculated by averaging the intensity function over configurations of the atoms in a cellular ``free-volume'' configuration space corresponding to single cell occupancy. A zero-order approximation to the derived scattering equation leads to the conventional x-ray scattering equation. A slightly better approximation is also shown.
Substituted Methanes. XV. Infrared Spectral Data, Assignments, and Calculated Thermodynamic Properties for Fluorotrichloromethane
Authors: Bernstein Richard B. , Zietlow James P. , Cleveland Forrest F.
Published: January 2005

Infrared spectral data for gaseous CCl3F have been obtained in the region 400–3200 cm−1, using NaCl and KBr prisms. The present data are compared with previous Raman and infrared data, and assignments and calculated wave numbers are given. The fundamentals (*=liquid) are ν1(a1) 1085, ν2(a1) 534, ν3(a1) 351,* ν4(e) 846, ν5(e) 400,* and ν6(e) 245* cm−1. Thermodynamic properties were calculated for 17 temperatures from 100° to 1500°K and were compared with previous calorimetric results.
A New Determination of the Half-Life of Am242m; the Problem of Counting Short-Lived Activities
Authors: Keenan Thomas K. , Penneman Robert A. , McInteer B. B.
Published: January 2005

The half-life of Am242m has been redetermined to yield a value of 16.01±0.02 hours (99 percent confidence level). A simple relationship is developed between experimentally measured average counts/minute and true dN/dt; a convenient rule of thumb states that there is <0.1 percent error between average disintegration rate (finite counting interval) and dN/dt (at the mid-point of the counting interval) when the counting interval does not exceed 20 percent of the half-life.
Investigations on Silver Sulfide
Authors: Wagner Carl
Published: January 2005

The variability of the Ag/S ratio in silver sulfide has been studied with the help of electrochemical measurements. Silver sulfide coexisting with metallic silver at 200°C contains a silver excess of 2.0×10−3 g-atom Ag/mole Ag2S, whereas silver sulfide coexisting with liquid sulfur has very nearly ideal stoichiometric composition. The variability of the Ag/S ratio in β Ag2S at 160°C is of the order of 3×10−5 g-atom Ag/mole Ag2S.

The interdiffusion coefficient of silver in Ag2S at 220°C is about 3×103 times greater than the self-diffusion coefficient of silver in Ag2S.

A thermodynamic calculation gives the result that the transformation temperature of Ag2S coexisting with metallic silver is about 1.7°C lower than the transformation temperature of Ag2S coexisting with liquid sulfur in accordance with observations made by Kracek.
The Thermodynamics of Reversible Galvanic Cells in Which the Compositions of Some of the Phases Vary with Temperature
Authors: Stout J. W.
Published: January 2005

The entropy change calculated from the temperature coefficient of electromotive force of a reversible galvanic cell, in which the compositions of some of the phases vary with temperature, corresponds to a unique correct chemical reaction. The equivalence of methods suggested by Barieau and by Li for determining this correct reaction is shown. The method of Barieau is simpler and more direct and presents the results in a more convenient form.
Segmental Mobility of Polymers Near Their Glass Temperature
Authors: Bueche F.
Published: January 2005

Glass forming polymers exhibit a rapid rise of activation energy for molecular motion as T is lowered through the glass temperature. This phenomena is explained here in two different but largely equivalent ways. The first method assumes that in order for a polymer segment to move (i.e., rotate or jump) an energy greater than a critical energy E must be localized on it and its neighbors. The second approach stipulates that a segment may not move unless more than a certain critical amount of free volume is associated with it and its neighbors. Both approaches lead to good agreement with experimental data available for polystyrene and polyisobutylene. The critical values of E and the free volume for these polymers are found and shown to be reasonable. Conclusions are drawn concerning factors influencing the glass temperature.
The Crystal and Molecular Structure of Tetraborane
Authors: Nordman Christer E. , Lipscomb William N.
Published: January 2005

The molecular structure of tetraborane B4H10 has been determined from 616 observed reflections from single crystals. The ordered phase is monoclinic P21/n, with four molecules in a unit cell with parameters, a=8.68, b=10.14, c=5.78A, and β=105.9°. Complete three-dimensional Fourier syntheses, including one from which the boron atoms had been subtracted, were employed to locate unambiguously the positions of all atoms.

Molecular dimensions indicate that the isolated molecule has symmetry C2v. The boron atoms form two triangles BIBIBII with a common edge BI–BI the angle between the planes of the triangles being 118.1°. Each of the two BI borons has one attached hydrogen atom, and each BII has two attached hydrogen atoms. The remaining four hydrogen atoms form bridges between the four BI–BII pairs. Molecular parameters are four BI–BII=1.845±0.002A, BI–BI=1.750A, BII–BII=2.786A, six B–H=1.11±0.04A, four BI–H (bridge)=1.21±0.03A, and four BII–H (bridge)=1.37±0.10A. Mean values and their average deviations have been given on the assumptions that the molecular symmetry is C2v and that the six B–H distances are equal.

There is an interesting false, incorrect structure which almost satisfies the x-ray diffraction data.

A metastable modification, obtained by sudden freezing of the super-cooled liquid, has spherically disordered molecules in hexagonal close packing. There are two molecules in a unit cell of dimensions, a=5.79 and c=9.36A.
The Heat Capacity of Thorium Dioxide from 10 to 305°K. The Heat Capacity Anomalies in Uranium Dioxide and Neptunium Dioxide
Authors: Osborne Darrel W. , Westrum Edgar F.
Published: January 2005

The heat capacity of thorium dioxide was determined from 10 to 305°K in an adiabatic calorimeter. As expected, no anomaly was observed in the heat capacity. The enthalpy, entropy, and free energy were calculated from the heat-capacity data and are tabulated for several temperatures. At 298.16°K the entropy and the enthalpy are, respectively, 15.593±0.02 cal deg−1 mole−1 and 2524.4±3 cal mole−1. By assuming the lattice entropy of uranium dioxide and of neptunium dioxide to be equal to the entropy of thorium dioxide, the magnetic entropy contributions at 298.16°K were evaluated as 3.0 cal deg−1 mole−1 for uranium dioxide and 3.6 cal deg−1 mole−1 for neptunium dioxide. These values are somewhat greater than the spinonly values (R ln 3=2.18 cal deg−1 mole−1 for uranium dioxide and R ln 4=2.75 cal deg−1 mole−1 for neptunium dioxide). The entropies of the other isomorphous actinide dioxides at 298.16°K are estimated to be (in cal deg−1 mole−1) 17.8 for PaO2, 19.7 for PuO2, 20.0 for AmO2, 20.3 for CmO2, 20.6 for BkO2, and 20.3 for CfO2.
Mean Dimensions of Rubber-Like Polymer Molecules
Authors: Wall Frederick T.
Published: January 2005

The mean square end-to-end separations of coiling type polymer molecules have been calculated by two different approximate methods, taking into account the effect of excluded volumes. One of the methods is the equivalent of a first-order perturbation calculation using the unrestricted random walk as a starting approximation. The other method involves the use of certain plausible functional forms valid for large values of the chain lengths. The calculations have been carried out for three, two, and one dimensions and the results are analyzed to provide an insight into factors which might determine convergence or divergence of the quotient 〈rn2〉Av/n (the mean-square length divided by the number of links). It appears that the quotient converges in three (or more) dimensions, but diverges for a lower number of dimensions.
The Mean Amplitudes of Thermal Vibrations in Polyatomic Molecules. II. An Approximate Method for Calculating Mean Square Amplitudes
Authors: Morino Yonezo , Kuchitsu Kôzo , Takahashi Akira , Maeda Keiji
Published: January 2005

A simple method of the calculation of the mean amplitudes of both directly bonded atom pairs and nonbonded ones is proposed by approximating the function cothx by 1/x+x/4. The enumeration of the L matrix, the most time-consuming procedure, is replaced by the calculation of the inverse matrix F−1 from the potential energy matrix. The formulae obtained are applicable with reasonable accuracy (4 percent) to almost all the cases except the atom pairs having higher frequencies than 1200 cm−1. For the latter cases modified formulas are presented by using hyperbolic cotangent function.

It is also revealed that, if some allowance be made for the errors of the mean amplitudes, a definite value can be assigned to the mean amplitude of a given pair of atoms, without referring to the structure of the other part of the molecule. Reliable values of the mean amplitudes are computed for some typical atom pairs, by the use of the force constants of Urey-Bradley type obtained by the analysis of the vibrational spectra.
K Fine Structure in the 2ν1 Band of CHD3
Authors: Wiggins T. A. , Shull E. R. , Bennett Jean M. , Rank D. H.
Published: January 2005

The K structure in the P and R branches of the 2ν1 band of CHD3 has been resolved permitting the determination of the following molecular constants: ν0=5865.02, B″=3.2777, B′=3.2396, A′—A″=−0.0181, DJ=3.9×10−5, and DJK=−4×10−5 cm−1. The Q branch is synthesized from these data and compared with the spectrometer trace of that branch.
Dielectric Polarization and Structure of Polar Liquids under Pressure
Authors: Harris Frank E. , Haycock Ernest W. , Alder Berni J.
Published: January 2005

The static dielectric constants of n-butyl alcohol, t-butyl alcohol, n-butyl chloride, n-butyl bromide, t-butyl chloride, and water were experimentally determined over a temperature range of 14° to 50°C and over a pressure range of 1 to 200 atmos. In addition, for glycerol, both the static dielectric constant from −18° to 14°C and the dielectric relaxation data at 0°C and up to 1.5 mc were obtained over the same pressure interval. The theory of dielectric polarization was then applied to these measurements to determine the molecular interaction. On the basis of the molecular interaction, structures and structure changes with temperature and pressure have been proposed for the various liquids studied.
Temperature Independent Factor in the Relative Rates of Isotopic Three Center Reactions
Authors: Bigeleisen Jacob , Wolfsberg Max
Published: January 2005

It is shown that the theoretical equation for the ratio of the rate constants of isotopic molecules is essentially independent of whether the crossing of the barrier is treated as a translation or a vibration. The temperature independent factor in this equation is evaluated for the case of substitution or displacement reactions. Calculations are presented for several cases involving the isotopes of carbon where there is simultaneous bond rupture and bond formation.
Distribution of Solute in Crystals Grown from the Melt. Part II. Experimental
Authors: Burton J. A. , Kolb E. D. , Slichter W. P. , Struthers J. D.
Published: January 2005

Experiments have been performed on the distribution coefficients of a number of solute elements in germanium crystals grown from the melt. The variation of distribution coefficient with conditions of crystallization is examined in the light of the theory of Part I. The incorporation of solute elements into the crystal is shown to depend critically upon the transport processes occurring in the melt.
The Quantum Mechanics of Collisions between Diatomic Molecules
Authors: Curtiss C. F.
Published: January 2005

The quantum mechanics of collisions between diatomic molecules is discussed. Explicit expressions for the angular transition probabilities are obtained. These expressions are in terms of a set of coefficients which are defined by the asymptotic form of the solutions of a set of coupled differential equations in one variable, the separation of the molecules. The coupled differential equations involve integrals of the intermolecular potential function, which may be of any form. A solution of the coupled differential equations by a perturbation method, which is valid in the case of low-energy collisions, in which transitions occur rarely, is discussed.
On the Theory of the Virial Development of the Equation of State of Monoatomic Gases
Authors: Riddell R. J. , Uhlenbeck G. E.
Published: January 2005

The problem of the condensation of a gas is intimately related to the asymptotic behavior of the virial coefficients, Bm, as m→∞. The problem of the evaluation of the virial coefficients may be divided into two distinctly different ones. The first of these, which is purely combinatorial in nature and is independent of the intermolecular force law, is that of determining the number of a certain type of connected graphs of l points and k lines which are called ``stars.'' This problem is solved by means of generating functions, with the result that the total number of such stars is asymptotically equal to (12l(l−1)k),for almost all k. Arguments are also presented which indicate that the total number of topologically different stars is 1l!(12l(l−1)k).With these results the combinatorial problem is essentially solved.

The second problem is that of evaluating certain integrals of functions which depend on the intermolecular potential. This problem is not so near to a solution. For a purely repulsive force, asymptotic expressions are obtained for k=l, and k=l+1. The partial contributions to the virial coefficient in these two cases are: (−1)l·53(52π)12(2b)l−1(l−1)l5/2,and (−1)l2·5324π3(2b)l−1,respectively. Results for some simple one-dimensional rigid lines are also given.
The Application of Jacobians to Statistical Thermodynamics
Authors: Einbinder Harvey
Published: January 2005

Shaw's Jacobian method for calculating thermodynamic derivatives is extended so that any partial second derivative can be expressed in terms of two sets of reference derivatives based on the independent variables (V, T) and (P, T), respectively. A simplified and enlarged table of second-order Jacobians is given in terms of these reference sets. Methods are developed for obtaining the reference J's explicitly in the cases of greatest importance in statistical thermodynamics, i.e., from A, E, the partition function and the caloric equation PV=sE, permitting any first or second partial derivative to be found as an explicit function of (V, T). These J's are given for the polyatomic ideal and van der Waals gases, black-body radiation, the general (relativistic and nonrelativistic) quantum gas, and the general degenerate Bose-Einstein and Fermi-Dirac gases. Their great usefulness is illustrated, and the possible application of reference Jacobians in evaluating semi-empirical theories of liquids and gases is noted. Finally, the classical theory of thermodynamic fluctuations is extended using Jacobians. General formulas are derived which give explicitly the total variance, partial variance, and covariance of the fluctuation of any thermodynamic variable from its equilibrium value.
Electronic Properties of Carbons and of Their Interstitial Bisulfate Compounds
Authors: Kmetko E. A.
Published: January 2005

The conductivity of graphite increases when it is oxidized into graphite bisulfate, this being the result of the expulsion of resonance electrons by the negative ions and the resulting creation of excess holes in the π-band. This study concerns the electronic properties of the bisulfate compounds formed by the oxidation of carbons in sulfuric acid, the range of heat-treatment of carbons extending from 1400°C (baked carbons) to 3000°C (polycrystalline graphite). The resistivities of all samples thus treated decrease with increase in the degree of oxidation. The rate of decrease in resistance depends upon the heat-treatment, the rate being increasingly greater for samples treated to higher temperatures. The curve of the Hall constant of unoxidized carbons versus the heat-treatment temperature H has a sharp positive peak at about H=2000°C. The curve rapidly drops on either side of the peak, the coefficient becoming negative and exhibiting a minimum around H=1400°C.

The thermoelectric power of all samples studied becomes more positive with oxidation, with maxima appearing for lamellar compounds. The rate of the initial rise is greater for higher heat-treatment temperatures. The temperature coefficient of resistance depends strongly upon the ion concentration, changing from negative to positive for carbons heat-treated above 2000°C. On the other hand, the coefficients remain negative and are remarkably independent of ion concentration for carbons treated to temperatures below 2000°C.

The results are in general consistent with the electronic model for carbons proposed by Mrozowski whereby the Fermi level is initially depressed during devolatilization of the hydrocarbon material by the formation of a large number of excess holes (heat-treatments below 1400°C) and later steadily rises with the growth of the crystallites towards the top of the π band, the growth of the crystal planes resulting also in a steady decrease of the energy gap between the π and conduction bands. The negative Hall coefficient for baked carbons indicates the π band to be so depleted that the Fermi level drops at least partially below the inflection curve. At room temperature the conduction is therefore semi-metallic in nature for carbons treated to H<2000°C in contrast with cases for which H>2000°C where the number of excess holes is relatively small and the current is carried mainly by the holes and electrons thermally activated into the conduction band.
A Sum Rule for the Vibrational Frequencies of Homologs
Authors: Bernstein H. J. , Pullin A. D. E.
Published: January 2005

It is shown empirically that the zero-point energy in substituted methanes may be treated as a constitutive property when account is taken of the interaction between nonbonded atoms. Thus, the sum of the vibration frequencies (Σν) of the halogenated methanes is found to have the predicted quadratic dependence on the number of substituents. This reduces to a linear dependence in the case of isotopically substituted homologs, compared to the linear dependence for Σν2 found theoretically by Decius and Wilson, and Sverdlov. Both Σν and Σν2 give good agreement between observed and calculated results. Various applications are given for the Σν rule and it is shown further that Σν, Σν2, Σ1/ν, Σ1/ν2 are all approximately constitutive properties of the halogenated methanes.
On the Stability of Metallo-Organic Compounds
Authors: Jaffé H. H. , Doak G. O.
Published: January 2005

It is pointed out that serious difficulties are encountered in preparing organic compounds of the transition elements. The hypothesis is proposed that these difficulties are caused by insufficient stability of the carbon-metal bonds involved. Some rough calculations based on Mulliken's ``magic formula'' are used to test this hypothesis. The results obtained indicate that carbon-metal bonds formed by the transition elements are extremely weak. The calculations further suggest that carbon-metal bonds involving the alkali and alkaline earth metals are largely ionic.
Electric Polarizability of Polar Ions
Authors: Mysels Karol J.
Published: January 2005

Polar ions are compared with well-known uncharged dipoles with respect to their polarizability and the contribution to the dielectric constant of their solutions. It is shown that (1) hydrodynamic forces exerted by the solvent on the solvated ion have to be taken into account in any kinetic discussion of dielectric behavior. (2) For ions having a symmetrical shape the polarizability is the same as that of an uncharged dipole obtained by adding, at the center of symmetry of the ion, a neutralizing charge. (3) The same effective dipole enters into the thermodynamic considerations of unsymmetrical ions. (4) The dipole analogy may be extended to the general case, leading to a rigorous but implicit expression. (5) As a first approximation, the polarizability of an ion is an indication of its dissymmetry.
The Effects of Interactions in Real Polymer Chains
Authors: Bueche F.
Published: January 2005

The effect of interactions between the segments of a polymer chain on the size of the molecule has been calculated. Two approaches have been used. The first is a direct probability calculation using an exponential interaction energy between segments. The second follows the original approach of Flory but solves the problem to a different approximation. Both methods lead to essential agreement with Flory's result for small and moderate interactions. A probable reason for the spurious results found by others is proposed.
Entropy Changes in Free Radical Reactions
Authors: Trotman-Dickenson A. F.
Published: January 2005

The entropies of alkyl and other simple free radicals may be estimated with sufficient accuracy to make informative calculations about the equilibria involved in the reactions of these radicals. Such calculations have been made for metathetical reactions, the decomposition of saturated molecules, and the decomposition of free radicals. The method provides a means of obtaining knowledge about reactions which are not readily susceptible to direct experimental investigation. The deviations of the frequency factors of some unimolecular decompositions from a value of 1013±1 are discussed.
Neutron Diffraction and Atomic Distribution in Liquid Lead and Liquid Bismuth at Two Temperatures
Authors: Sharrah Paul C. , Smith G. Pedro
Published: January 2005

Neutron diffraction patterns have been obtained on liquid lead and liquid bismuth at two temperatures. The patterns differ only slightly at the different temperatures, the main peak being slightly shorter and broader and shifted slightly to smaller angles at the higher temperatures. The diffraction patterns have been analyzed to obtain information on the atomic distribution. The first main peak in the distribution curve for liquid lead is at 3.40A and represents about 9.4 atoms. The first main peak in the curve for liquid bismuth is at 3.35A and represents about 7.7 atoms. The second most prominent concentration of atoms occurs at 6.6A for both lead and bismuth.
On Drickamer's Modification of the Theory of the Thermal Diffusion Column
Authors: Hirota Kozo , Kobayashi Yasushi
Published: January 2005

By use of thermal diffusion columns, the N2–H2 system has been separated continuously and its thermal diffusion ratio α has been determined with a method of least ambiguity under a pressure range of 1∼12.6 atmos. The α-values thus obtained, based on the Furry-Jones theory of the apparatus, have been found to be not constant and also to differ very much in most cases from those hitherto reported. However, the values corrected according to the theory modified by Drickamer et al. have been shown to be reasonable, supporting their modified theory.
Some Overlap Integrals Involving d Orbitals
Authors: Jaffé H. H.
Published: January 2005

Formulas are presented for overlap integrals for overlap of dπ with pπ and dπ orbitals, and for dδ with dδ orbitals. Slater AO's were used throughout. Numerical tables for these integrals for a variety of values of the parameters ρ and τ are given.
A Semi-Empirical Equation for the Vapor Pressure of Liquids as a Function of Temperature
Authors: Frost Arthur A. , Kalkwarf Donald R.
Published: January 2005

The slight reverse curvature in the plot of logP versus 1/T (P, vapor pressure; T, absolute temperature) may be explained on the basis of the nonideal behavior of the vapor together with the change in heat of vaporization with temperature. If it is assumed that ΔH is linear with T and that the van der Waals a/V2 term is a first approximation to the deviation from the ideal, the following equation may be obtained by integration of the Clapeyron equation: logP=A+BT+C logT+DPT2.The last term is the nonideal gas correction with constant D=a/2.303R2. With constants A, B, and C determined empirically, the equation reproduces experimental vapor pressures from the triple point to the critical point with an average deviation of 0.3 percent.
Rotational and Vibrational ``Temperatures'' of CH in Flames at Atmospheric Pressure
Authors: Broida Herbert P.
Published: January 2005

Spectra of the R branch of the 2Δ—2Π transition of CH have been obtained from flames of acetylene, propane, and methane premixed with oxygen burning at atmospheric pressure. The distributions of rotational and vibrational intensities have been measured and compared with those expected from thermal excitation. Although in some flames the distributions are close to thermal, the majority of distributions indicate that the excited CH is formed by a nonthermal process and is unreliable as a temperature indicator. The suppression of predissociation of CH in rich hydrogen flames with added acetylene has also been investigated. A continuous emission reaching a maximum near 4000A has been measured.
Some Thermal Reactions of the Higher Iron Carbides
Authors: Cohn Ernst M. , Hofer L. J. E.
Published: January 2005

One of the undesirable side reactions of the Fischer-Tropsch synthesis is deposition of carbon. To ascertain whether thermal reactions of iron carbides might cause this deposition and to learn more about the nature of iron carbides, the transition from hexagonal close-packed (h.c.p.) iron carbide to Hägg iron carbide and the reaction of higher iron carbide with metallic iron to form cementite have been studied in a copper- and alkali-promoted iron catalyst by means of a magnetic balance.

The transition from h.c.p. to Hägg iron carbide is heterogeneous, with no apparent change of the compositions of both carbides, nor any detectable solubility of one carbide in the other. The data confirm the narrow range of composition of Hägg carbide and the fact that it contains somewhat more iron than corresponds to the formula Fe2C.

The synthesis of cementite from metallic iron and higher iron carbide proceeds via Hägg carbide and only above about 320°C. It does not go to completion up to 440°C; above that temperature, decomposition of Hägg carbide into cementite and free carbon is sufficiently rapid to prevent completion of the synthesis.

The data show that deposition of carbon on iron catalysts during the Fischer-Tropsch synthesis is not caused by thermal reactions of iron carbides, unless h.c.p. iron carbide should contain more carbon than Hägg iron carbide. A possible explanation of the apparent stabilizing effect of copper on h.c.p. iron carbide is given.
The Infrared and Raman Spectra of SiH2Cl2
Authors: Hawkins Janet A. , Wilson M. Kent
Published: January 2005

An investigation of the infrared spectrum of gaseous SiH2Cl2 and the Raman spectrum of liquid SiH2Cl2 results in the following fundamental assignment: ν1(a1)=2200 cm−1,ν2(a1)=953 cm−1,ν3(a1)=531 cm−1,ν4(a1)=188 cm−1,ν5(a1)=710 cm−1,ν6(b1)=2200 cm−1,ν7(b1)=810 cm−1,ν8(b2)=877 cm−1,ν9(b2)=592 cm−1.

Thermodynamic functions for SiH2Cl2 were calculated with the usual assumptions. The infrared spectrum of gaseous CH2Cl2 and the infrared and Raman spectrum of liquid CH2Cl2 were remeasured.
The Infrared Spectra of Tetranitromethane
Authors: Lindenmeyer P. H. , Harris P. M.
Published: January 2005

Cooling curve investigations show that the transition between the two crystalline forms of tetranitromethane occurs at −99.8°C and its character suggests an order-disorder transformation. The infrared spectra of tetranitromethane were obtained at 25°C (vapor), 18°C (liquid), −40°C (solid I), −88°C (solid I), −104°C (solid II) and −126°C (solid II). The spectra of the vapor are best interpreted by a molecule with S4−4̄ symmetry whereas reported Raman spectra indicate D2d−4̄2m symmetry in the liquid. Satisfactory agreement between these and the x-ray diffraction data require molecules of both symmetries. A complete lack of selection rules was observed in the spectra throughout the solid range.
The Entropy and Low Temperature Heat Capacity of Neptunium Dioxide
Authors: Westrum Edgar F. , Hatcher J. B. , Osborne Darrell W.
Published: January 2005

The heat capacity of a two-gram sample of neptunium dioxide was determined from 10 to 315°K in an adiabatic calorimeter. At 298.16°K the molal entropy and enthalpy calculated from the heat capacity data are 19.19±0.1 cal deg−1 and 2770±15 cal, respectively. A pronounced hump was found in the heat capacity curve of neptunium dioxide at 25.3°K similar to that found by Jones, Gordon, and Long in uranium dioxide at 28.7°K. This anomaly in the heat capacity is suggestive of a cooperative phenomenon and is attributed to the incidence of antiferromagnetism below the temperature of the maximum in the heat capacity. A calorimeter for gram scale samples and a modification of the cryostat design of Ruehrwein and Huffman so as to employ only liquid helium and liquid nitrogen as refrigerants are described.
On the Radiofrequency Spectrum of the Components of a Sodium Chloride Beam. The Dimerization of the Alkali Halides
Authors: Ochs Stefan A. , Coté Robert E. , Kusch P.
Published: January 2005

The transitions ΔmI=±1, ΔmJ=0 for both Na and Cl were studied at high magnetic field in a beam produced by the evaporation of sodium chloride. The observed spectra could not be fully described in terms of the known internal interactions of a diatomic molecule or the interaction of a diatomic molecule with an applied field. It is suggested that the unexplained features of the spectra result from the presence in the beam of molecules of the type (NaCl)2. Similar effects have been observed in sodium fluoride and sodium iodide.
A Semi-Empirical Theory of the Electronic Spectra and Electronic Structure of Complex Unsaturated Molecules. I.
Authors: Pariser Rudolph , Parr Robert G.
Published: January 2005

A semi-empirical theory is outlined which is designed for the correlation and prediction of the wavelengths and intensities of the first main visible or ultraviolet absorption bands and other properties of complex unsaturated molecules, and preliminary application of the theory is made to ethylene and benzene.

The theory is formulated in the language of the purely theoretical method of antisymmetrized products of molecular orbitals (in LCAO approximation), including configuration interaction, but departs from this theory in several essential respects. First, atomic orbital integrals involving the core Hamiltonian are expressed in terms of quantities which may be regarded as semi-empirical. Second, an approximation of zero differential overlap is employed, and an optional uniformly charged sphere representation of atomic π-orbitals is introduced, which greatly simplify the evaluation of electronic repulsion integrals and make applications to complex molecules containing heteroatoms relatively simple. Finally, although the theory starts from the π-electron approximation, in which the unsaturation electrons are treated apart from the rest, provision is included for the adjustment of the σ-electrons to the π-electron distribution in a way which does not complicate the mathematics.

Electronic energy levels in the theory are expressed in terms of ionization potentials of atoms, resonance integrals of bonds, Coulomb repulsion integrals between two π-electrons on the same atom and between two π-electrons on different atoms, and penetration integrals between π-electrons and neutral atoms. Preliminary applications to ethylene and benzene in which only the carbon-carbon resonance integral is treated as an empirical quantity show that the theory can reproduce the results of the purely theoretical method with very little labor. The reasonableness of considering all of the above quantities as semi-empirical is pointed out, however, and it is through a detailed examination and exploitation of this in the second paper of this series that correction for the inadequacies of the π-electron approximation is made and improved agreement with experiment is attained.
The Hydrodynamic Stability of Flame Fronts
Authors: Einbinder Harvey
Published: January 2005

The hydrodynamic stability of a plane flame of finite thickness is treated by investigating the temporal behavior of first-order infinitesimal disturbances. This work is a generalization of earlier studies and takes into account the effect of distortion on burning velocity. The general equations of motion for the disturbance in a viscous gas under the influence of gravity are derived and solved. Horizontal and upward propagating plane flames are always unstable and those propagating downward are unstable under most conditions, so their measured transformation velocity under such conditions does not equal the stationary burning velocity. The calculated maximum cell size for downward propagation (λmax=32UuUb×10−4 cm) and the cell size for a flame propagated by thermal conduction (λthermal=22k/CpρuUu ) are in good agreement with existing experimental observations. The variation of cell size with pressure yields the pressure dependence of the burning velocity. The sudden appearance of cells in slow hydrocarbon flames (Uu≈10 cm/sec) observed at stoichiometric in going from lean to rich mixtures, indicating a corresponding decrease in flame thickness, is advanced as provisional evidence of a shift in the dominant propagation mechanism in these flames—from diffusion by atomic radicals for lean flames to thermal conduction for rich ones.
Electric Resistivity of Interstitial Compounds of Graphite
Authors: Mrozowski S.
Published: January 2005

Assuming that the formation of interstitial compounds is accompanied by creation of excess holes in the otherwise full band of graphite, it is shown that a linear energy-momentum relation at the Brillouin zone corners is incapable of explaining the decrease of the electric resistance with oxidation. It appears that for a more general model the decrease in relative resistance should be independent of temperature for large oxidations if suitable corrections for the initial conditions are made. Data for polycrystalline graphite corrected for the existence of an energy gap and of excess holes in the untreated material give curves which converge for higher oxidation with the curve for natural graphite. Discussion of the low temperature properties of graphite leads to the conclusion that large graphite crystals possess slightly overlapping zones.
The Asymmetric Rotor. XI. Hydrogen Sulfide Absorption in the Regions 8700 cm−1 and 11 000 cm−1
Authors: Innes K. Keith , Cross Paul C. , Bair Edward J.
Published: January 2005

By the use of a 21-foot grating spectrograph and absorbing paths of up to 350 feet, sixty lines in the region from 10 870 cm−1 to 11 100 cm−1 have been measured and analyzed as the rotational structure of an A-type band. It may be identified as the lower component of the resonating pair (nσ, nπ, nδ)=(131), (311).

Most of the more than eighty hydrogen sulfide absorption lines measured between 8560 and 8830 cm−1 have been assigned to an A-type band identified as the lower component of the (121), (301) resonating pair. Several additional lines definitely not due to water appear to indicate the existence of a superimposed B-type band having about the same upper state parameters, presumably the lower component of the pair (211), (031). In cm−1, ν0=8697.3    A*=10.29   B*=8.75    C*=4.48ν0=11008.78  A*=10.197  B*=8.559  C*=4.411.
Excited Electronic States and Molecular Vibrations of Thiophosgene
Authors: Duchesne Jules
Published: January 2005

The most general vibration potential function of the lower excited electronic state of thiophosgene is computed and interpreted in terms of theory. It is shown that the π* antibonding orbital is not far from being localized in the CS bond and that the sulfur lone pair electrons play a great part in the angular rigidity of the molecule. A general rule for the behavior of the sign of the cross terms is formulated.

A preliminary study of the next excited state is undertaken and a correlation between some properties of the molecular orbitals of both states is made.
The Energies of Strained Carbonium Ions
Authors: Franklin J. L. , Field F. H.
Published: January 2005

The appearance potentials of two sterically hindered nonplanar carbonium ions (from bicyclo [2.2.1] heptyl bromide and bicyclo [2.2.2] octyl bromide) are found to be higher than the appearance potential of an analogous planar carbonium ion. From these results it is inferred that in general the appearance potentials of unhindered ions correspond to the formation of the ions in essentially equilibrium configurations.
The Effect of Pressure on Diffusion in Aqueous and Alcoholic Salt Solutions
Authors: Cuddeback R. B. , Drickamer H. G.
Published: January 2005

Diffusion coefficients have been measured as a function of pressure to 10 000 atmos for the following aqueous solutions: 0.1 N Hg(NO3)2 at 0∘, 25∘, 50∘,75∘C,0.1 N CaCl2    at 25∘, 50∘C,0.1 N Ca(NO3)2 at 25∘C,0.1 N TlNO3    at 25∘C,and for 0.01 M HgCl2 in n-butanol at 25° and 50°C. The results are interpreted in terms of the activation volume, and compared with previous data on water and sulfate solutions.
Stress Relaxation in Elastomers
Authors: Bueche A. M.
Published: January 2005

The process of chemical stress relaxation in elastomers is examined in some detail. It is predicted that in some cases it will be possible to determine the location of the chemical bond broken. The special cases of relaxation due to scission of cross links and random scission of the polymer are calculated. The shapes of the stress vs time curves are widely different.
Analysis of the Spectrum of the Nd+++ Ion in the Bromate Crystal
Authors: Satten Robert A.
Published: January 2005

The absorption spectrum of single crystals of Nd(BrO3)3·9H2O was photographed in the visible and near infrared and ultraviolet in σ and π polarizations. Empirical energy level diagrams are presented for some of the groups of lines, and in this way it is found that the 4I9/2 ground state is split in the electric field into five levels at 0, 115, 184, 363, and 382 cm−1. An analysis is made of the spectrum based on a Russell-Saunders coupling model and a knowledge of the expected splitting of the levels of the free Nd+++ ion in the electric field of the crystal. The electrostatic interaction energies of terms arising from f3 electrons were computed by the Slater method and the results agree with those previously given by Racah. The Landé interval factors were also computed in order to predict the multiplet splitting. Trial values of the parameters were first found by extrapolation mainly from Pr+++. Selection rules for transitions in an electric field of C3v symmetry are presented, and the results applied to the neodymium bromate spectrum indicate that the transitions are not purely electric dipole, quadrupole, or magnetic dipole alone.
Some Absorption Bands in the Far Infrared
Authors: O'Loane J. Kenneth
Published: January 2005

The following bands have been located in the far infrared spectra by the method of residual rays: cis-dichloroethylene at 170 cm−1; trans-dichloroethylene at 265 cm−1 and 192 cm−1; phosphorus trichloride at 190 cm−1; trans and ``gauche'' 1,2 dichloroethane at 223 cm−1 and 125 cm−1; propylene at 177 cm−1; acetaldehyde at 245 cm−1 and 120 cm−1; methyl alcohol at 190 cm−1, 161 cm−1, and 120 cm−1; carbon suboxide at 192 cm−1.
The Fluorescence of Biacetyl Vapor
Authors: Groh Harold J.
Published: January 2005

It has been shown that the fluorescence of biacetyl vapor at 25°C excited with 3650A radiation does not decay as a simple exponential function of time. After flash excitation, there is a ``fast'' fluorescence followed by a slow exponential decay. The quenching of the fluorescence has also been studied at several temperatures, pressures, and in the presence and absence of oxygen gas. A consideration of this and previous work permits a further elucidation of the fluorescence phenomena in terms of two upper emitting states. Fluorescence from the state responsible for most of the fluorescence at room temperature is quenched strongly by oxygen and is apparently completely removed at 200°. Fluorescence from the other state is unaffected by oxygen and is still measurable at 200°.
Effect of Spectral Line Shape on Apparent Rotational Temperatures of OH
Authors: Penner S. S.
Published: January 2005

The effect of spectral line shape on apparent rotational temperatures of OH has been investigated for the P1 branch, 2Σ→2Π transitions, (0, 0) band, by treating the ratio of collision half-width to Doppler half-width as a variable parameter. The results of calculations for emission experiments, using conventional plots, show a large effect of line shape on apparent temperature. In general, the greater the ratio of collision half-width to Doppler half-width, the smaller the distortion of experimental data. The analysis predicts higher apparent rotational temperatures for isothermal systems at reduced pressures than at atmospheric pressures. Although this result is in agreement with experimental observations on flames, it cannot be used as an explanation for the observed data without auxiliary studies proving that distortion of data is of importance in any given case. The two-path method for determining temperatures and emissivities (concentrations) in flames has been extended to spectral lines with combined Doppler- and collision-broadening.
Normal Coordinate Treatment of Diacetylene
Authors: Ferigle Salvador M. , Weber Alfons
Published: January 2005

A normal coordinate treatment for diacetylene is carried out, using Wilson's FG matrix method. Different sets of potential constants are obtained from the observed frequencies, and limits for these constants are set. The values of the potential constants are discussed in connection with the molecular structure.
A Quantum-Mechanical Calculation of the Rates of Some Chemical Reactions
Authors: Bauer E. , Wu Ta-You
Published: January 2005

The rates of many simple chemical reactions of the type AB+C→A+BC are empirically known to be of the form kOF=PZ exp(—EA/kT). On the theory that the reactions take place through the interchange of translational and vibrational energy, a qualitative quantum-mechanical calculation of the rate kOF is made for the simple model of collinear collisions. The empirical values of the activation energy EA are employed to fix the interaction potential for a given reaction. On identifying the quantum-mechanical expression for the rate kOF with the empirical expression above and on using the gas kinetic expression for the mean number of collisions Z, it is possible to calculate the probability factor P. Numerical calculations have been carried out for the two reactions H2+X→HX+H, where X is Cl or Br. In both cases, P is found to be about 8×10−3.
Precision Measurements of the Enthalpy of KBr and KI at High Temperatures
Authors: Cooper Charles B.
Published: January 2005

By use of an ice calorimeter precision measurements of the enthalpies of pure samples of KBr and KI between 300°C and their melting points were made. Values for the specific heats at constant pressure of these substances through the same temperature range were calculated and tabulated.
Absorption Bands and Lines in Irradiated LiF
Authors: Delbecq Charles J. , Pringsheim Peter
Published: January 2005

The paper deals with a number of phenomena observed in lithium fluoride after formation of color centers by exposure to x-rays, Van de Graaff electrons, or neutrons and not observed in other alkali halides under similar conditions. The most important of these phenomena are: (1) The appearance of a new band at 222 mμ, when the crystal is bleached with light of wavelength 254 mμ absorbed in the F band, and the inverse effect by subsequent irradiation with light of shorter wavelengths. (2) The production of F centers in a crystal heated to temperatures up to at least 450°C. The higher the temperature at which the F centers were produced, the greater is the intensity of the band at 222 mμ obtained by subsequent optical bleaching of the F band at room temperature. (3) The appearance of fine structure in a relatively weak band with peak at 380 mμ and of a very weak line at 523 mμ when the spectrum is recorded at the temperature of liquid nitrogen. (4) The very strong increase in the intensity of the band at 380 mμ and the line at 523 mμ by irradiation with short wavelength ultraviolet. (5) The sharpness at low temperatures of the first line of the band at 380 mμ and the line at 523mμ. At the temperature of liquid helium their half-widths are of the order of 1A.
Effect of 3p Atomic Orbital on Energy of the Double Bond
Authors: Dooling J. S.
Published: January 2005

The energy of the π—π part of the double bond is calculated by (1) the perturbation method using the ``united atom'' model, and (2) the MO method where the wave function used is constructed as a linear combination of atomic orbitals, as a function of internuclear distance. In each case the wave function includes the 3p atomic orbital. The results of the investigation indicate (1) that the wave function ordinarily used in the MO method is not appreciably improved by the inclusion of the 3p atomic orbital, and (2) that the absolute value of the energy calculated by the MO method using p functions centered at the nuclei, is at least 20 percent too low at the distances occurring in the C–C bond.
Specific Heat of Diamond at Low Temperatures
Authors: DeSorbo Warren
Published: January 2005

Specific heat data on diamond at temperatures between 20° and 300°K are reported. Comparisons of the data have been made with the predictions of the Debye theory. The deviation of the specific heat from the value given by the three-dimensional continuum theory in the low temperature region can be qualitatively described in terms of a superposition of a simple Einstein frequency. It has been found that variations that occur in expressing reduced characteristic temperatures as a function of reduced temperatures for diamond are qualitatively similar to those of the face-centered cubic metals Al, Cu, and Ag.

The values of entropy, enthalpy, and free energy have been determined and tabulated at integral values of temperature from 25° to 300°K. The entropy of diamond at 298.16°K is 0.568±0.005 cal/g-atom/deg.
The Structure of Phosphine
Authors: Sirvetz Marshall H. , Weston Ralph E.
Published: January 2005

Several low J microwave transitions of PH2D and PHD2 have been observed in the K band. The effect of centrifugal distortion on the rotational levels has been taken into account approximately, with the result that errors in the computed structure due to this cause now appear to be negligible in comparison with those due to vibration-rotation interaction. One obtains for the P–H distance 1.4177 and 1.4116A in the two cases; for the H–P–H angle, 93°21.6′ and 93°15.4′. The dipole moment has been measured for both species with agreement within experimental error.