bluuebunny/crossref_metadata_2025 huggingface dataset:
SCF LCAO Study of Linear and Bent Acetylene
Authors: Burnelle Louis
Published: January 2005

The self-consistent field molecular orbital method has been applied to linear acetylene, and to the cis- and trans-bent molecule, for various values of the bending angle. All 14 electrons have been taken into account, and free inner-shell outer-shell mixing has been allowed. As for the multicenter integrals, they have been evaluated by the Mulliken approximation. Reasonable values are obtained for the first ionization potential and for the excitation energy corresponding to the first π→π* transition. The variation of the orbital energies induced by the distortion brings a confirmation of the qualitative predictions made by Walsh on the basis of the simple molecular orbital theory, but the treatment fails to predict the correct shape of the molecule in its first excited state, very likely because of the approximation of the three- and four-center integrals. The difference in energy between the cis- and the trans-configurations is predicted correctly, and there is a rough agreement between the calculated force constants and the experimental values. The results of an electron population analysis agree with experimental evidence and with the current views on hybridization, and they are confirmed by an examination of the equivalent orbital representation.
Molecular Association in Sodium Cyanide Vapor
Authors: Porter Richard F.
Published: January 2005

Mass spectra of vapors from samples of NaCN indicate that the compound evaporates as NaCN(g) and Na2(CN)2(g) molecules at temperature around 1000°K. The mass spectrum resembles that obtained for sodium halide and hydroxide vapors. A comparison of relative ion currents produced by electron bombardment of NaCN vapors effusing from single- and double-oven-type Knudsen cells, yielded information related to the processes of ion formation. For the reaction Na2(CN)2(g)=2NaCN(g),we obtain ΔH1000°=41.0±3.0 kcal/mole dimer. This indicates a dimer stability comparable to that for Na2I2(g).
Interpretation of the Absorption Spectra of K3Fe(CN)6
Authors: Naiman C. S.
Published: January 2005

By interpreting the absorption spectra of K3Fe(CN)6 in solution, we are able to explain the results of the pressure dependence of the solid spectra, obtained by Parsons and Drickamer.

The intense absorptions at 24 000 and 32 900 cm—1, are identified as charge-transfer spectra from the ligand to the T2g level of the metal ion, while the one at 38 460 cm—1 is identified as the same type of transition, but into the Eg level. Fitting of the weaker spectra yields the values of 3500, 720, and 3285 cm—1 for the crystalline field parameters Dq, B, and C, respectively.

One of the results of Parsons and Drickamer shows evidence of a charge-transfer transition that is symmetry restricted, and made allowed by vibrational-electronic perturbations. A perturbation treatment is carried out that follows the method developed by Liehr and Ballhausen for the dn→dn crystal-field transitions, that are also symmetry forbidden.

Finally, two types of experiments that would test the proposed explanations are described.
Thermal Conductivity and Equilibrium Constant of the System N2O4⇌2NO2
Authors: Srivastava B. N. , Barua A. K.
Published: January 2005

An all-glass apparatus has been used to measure the thermal conductivity of the system N2O4⇌2NO2 by the thick-wire variant of the hot-wire method in a temperature range of 32°—90°C and up to a pressure of about 50 cm Hg. The apparatus is capable of measuring the equilibrium constant and the thermal conductivity of the system simultaneously. The experimental data have been discussed in the light of theories based on the assumption of local chemical equilibrium. The discrepancy between the experimental and the calculated values of the heat conductivity which is particularly large at the lower pressures shows the necessity of applying nonequilibrium heat transfer theory to interpret the data.
Effect of Pressure and Temperature on the Absorption Spectra of Four Alkali Halide Phosphors
Authors: Balchan A. S. , Drickamer H. G.
Published: January 2005

The effect of pressure and temperature has been measured on the ``A''. bands in KI:Tl and in three alkali halides containing Pb++ impurity. The effect of temperature is to impose a red shift on the observed room-temperature pressure shift. The most remarkable result is the appearance of a new band in the high-pressure phase of KCl:Pb and KBr:Pb upon heating under pressure. The band remains after cooling, but disappears upon lowering the pressure into or through the region of the transformation back to the fcc phase. Repressuring and reheating reintroduces the band. It seems most probably that the band is associated with the ionic configuration near the Pb++ ion; especially with the location of the accompanying K+ vacancy.
Note on the Separability Theorem for Electron Pairs
Authors: Löwdin Per-Olov
Published: January 2005

It is shown that, if two functions ΛA(1, 2, 3,...p) and ΛB(1, 2′, 3′,...q′) describing two groups A and B of electrons are orthogonal with respect to electron 1 then there exists a complete orthonormal set of one-electron functions Φk(1) such that the functions actually occurring with nonvanishing coefficients in the expansion of one of the functions cannot simultaneously occur in the expansion of the other function. This is a generalization of a separation theorem recently found by Arai.
Hydrogen Bonding Interaction between Adsorbate Molecules and Surface Hydroxyl Groups on Silica
Authors: Basila Michael R.
Published: January 2005

The interactions of the surface hydroxyl groups on amorphous silica with two series of adsorbates, the methylbenzenes and the chloromethanes, have been studied. A correlation is demonstrated between the frequency shifts of the surface hydroxyl stretching vibration and the ionization potential of the adsorbate. A similar correlation is found for the interaction of the hydroxyl group of a carbinol with the methylbenzene series. The importance of charge-transfer interaction in hydrogen bonding, which is indicated by these correlations, is discussed.
Long-Range Nuclear Magnetic Shielding in Molecules and the Anisotropy in the Magnetic Susceptibility of a Carbon-Carbon Single Bond
Authors: Musher Jeremy I.
Published: January 2005

A method is discussed for obtaining quantitative measurements of long-range NMR shielding effects in molecules based on the theory of Ramsey as extended by McConnell. These effects are shown to arise principally from the diamagnetic part of the magnetic susceptibility of the individual bonds when the origin of coordinates is taken at the geometric center of the bond. Application is made to saturated hydrocarbon alcohols for which the only long-range shielding contributions come from tetrahedral carbon-carbon bonds. From high-resolution NMR measurements of tertiary protons on carbocyclic molecules the existence of these effects is verified and the magnitude of the magnetic anisotropy on the individual bonds causing such effects is determined.
Mean and Equilibrium Molecular Structures of Methane and Deuteromethane as Determined by Electron Diffraction
Authors: Bartell L. S. , Kuchitsu Kozo , deNeui R. J.
Published: January 2005

The structural parameters of methane and methane-d4 were determined with the new rotating-sector electron diffraction apparatus of Iowa State University. The results demonstrated, for the first time by electron diffraction, the existence of isotope effects on structure. Mean internuclear distances were C–H=1.1068±0.001 A, C—D=1.1027±0.001 A, H···H=1.811±0.007 A and D···D=1.805±0.008 A. Mean amplitudes, reckoned from mean positions, were C–H=0.0751±0.002 A, C—D=0.0663±0.002 A, H···H=0.120±0.006 A, and D···D=0.105±0.006 A.

The isotope effects were just those expected for atoms of different mass vibrating in identical anharmonic force fields. Vibrational anharmonicity led to measurable phase shifts in the molecular diffraction patterns from which the asymmetry of the internuclear distribution functions could be determined. This allowed a direct experimental determination of the approximate equilibrium C–H and C—D bond lengths, giving 1.082 A. Somewhat more rigorous calculations of the correction from mean to equilibrium distances based on an anharmonic Urey-Bradley field led to equilibrium C–H and C—D bond lengths of 1.0847 A and 1.0863 A, respectively. Corresponding equilibrium bond lengths computed from the spectroscopic r0 values of 1.0940 A and 1.0923 A, respectively, were 1.0850 A and 1.0856 A. The comparison clearly illustrates the appreciable difference between electron diffraction and spectroscopic methods in the manner of averaging over molecular motions, but also confirms the essential equivalence of molecular information derived, if suitable corrections are applied to each.
Low-Resolution Analysis of the n→π* (3000 A) Absorption Spectrum of s-Triazine
Authors: Brinen J. S. , Goodman Lionel
Published: January 2005

The 3000-A absorption band of s-triazine has been examined under low resolution. The long wavelength portion of this band is assigned to the allowed n→π* promotion A2′′1← A1′1 with 0–0 band at 31 574±15 cm—1. Evidence is presented for the onset of a second n→π* transition at ∼32 500 cm—1. The observed sequence of states contradicts previous predictions based on approximate sp2 hybridization, and indicates that in the excited states the n orbital has very little s character (∼0.1).
Unperturbed Mean-Square End-to-End Distance of Polyethylene
Authors: Hoeve C. A. J.
Published: January 2005

It is shown that previous methods for calculating the mean-square end-to-end distance 〈r02〉 of polyethylene are invalid, since no account is taken of interactions between rotations around chain bonds. With the aid of recently developed matrix methods the value of 〈r02〉/nl2 is calculated to be 6.75 at 160°C in excellent agreement with the results deduced from intrinsic viscosity measurements.
Paramagnetism of Tetraphenanthroline Dihydroxyl Diferric Chloride
Authors: Elliott Norman
Published: January 2005

The magnetic susceptibility of ferric o-phenanthroline has been measured and found to show abnormal temperature dependence. The results are explained in terms of an equilibrium between a singlet ground state and an excited triplet state of the dimer.
Statistical Computation of Reaction Probabilities. II
Authors: Wall F. T. , Hiller L. A. , Mazur J.
Published: January 2005

With the use of a high-speed digital computer, additional numerical calculations have been carried out to investigate the probability of exchange attending collisions of hydrogen atoms with hydrogen molecules. The computations were based on classical mechanics, although the potential energy was assumed to be given by the London-Eyring-Polanyi formula. Initial conditions of the particles involved were chosen by a pseudorandom process, and most of the interactions proved to be of the type that failed to produce exchange. Out of more than 700 computations, however, it was found that 6 involved exchange under circumstances suggesting a reasonable explanation. Sample results are displayed in graphical form showing internuclear separations as functions of time. It appears from the results that molecules with little or no rotational energy are more likely to exchange with a colliding atom than are molecules with substantial amounts of rotational energy. This can be simply explained by the fact that a non-rotating molecule can be readily constrained by an oncoming atom to a colinear configuration for which the activation energy is a minimum.
Structural Effects in the Vapor Pressures of Isotopic Molecules. O18 and N15 Substitution in N2O
Authors: Bigeleisen Jacob , Ribnikar Slobodan V.
Published: January 2005

The relative vapor pressure ratios of the isotopic N2O molecules have been determined by distillation in a column under total reflux. It is shown that the vapor pressures are in the sequence N14N14O16>N14N15O16>N15N14O16>N14N14O18.The absolute vapor pressure ratios have been determined from the kinetic behavior of the column and the decrease in separation by production from the column.

Theoretical calculations of the relative vapor pressure ratios can be made from the atomic masses and the random structure of liquid N2O. The calculated relative isotope effects are in good agreement with experiment. The absolute value of ln PN14N14O16/PN14N15O16 is calculated from the specific heat of N2O to be 8.2×10—4 at 184°K, in good agreement with the experimental value 7.8±1.4×10−4. The difference in vapor pressures of the isotopic isomers N14N15O16 and N15N14O16 is attributed to hindered rotation of the molecule in the liquid.
Equilibrium Degrees of Crystallization Predicted for ``Single Pass'' and Folded Chain Crystallite Models
Authors: Roe R.-J. , Smith K. J. , Krigbaum W. R.
Published: January 2005

The free energy change for the crystallization of a bulk polymer consists of two parts: the ``single crystal'' term exhibited by low molecular weight compounds, and that arising from the deformation produced in the intervening amorphous chains as crystallization proceeds. The latter term limits the degree of crystallinity which can be achieved in a polymeric material at a given temperature. Beginning with an initially unstretched, isotropic sample, the entropy change associated with the deformation of the amorphous chains is calculated for two models, in which the chain either passes through a crystallite once and departs, or folds back and forth within the crystallite several times before re-entering the amorphous region. The folded chain morphology imposes less strain upon the amorphous chains, and hence results in the development of higher degrees of crystallinity from the original isotropic melt. The folded chain model, in which the amorphous portions are represented by flexibly linked chains, gives good agreement with the observed equilibrium degrees of crystallinity, for high molecular weight fractions of polyethylene, over a considerable temperature range. An approximate treatment is also given for the molecular weight dependence of crystallinity at a fixed temperature.
Refinement of the B9H15 Structure and Test for Solid Solutions
Authors: Simpson Paul G. , Lipscomb William N.
Published: January 2005

Refinement of the x-ray diffraction data for B9H15 confirms the structure, establishes an x-ray criterion for crystal purity, and shows that the most difficult impurity to detect, namely, a possible B8 hydride, is not present in amounts greater than about 5% or so. Taking all observations of the x-ray investigations together, we conclude that the B9H15 single crystals were essentially pure.
Energy Levels of PrCl3
Authors: Margolis Jack S.
Published: January 2005

A review of the spectra of the Pr3+ ion in PrCl3 is presented and the spectra are reanalyzed by means of a more complete Hamiltonian than has been previously used. This new Hamiltonian includes a complete calculation of the crystalline field interaction for a field of D3h symmetry, and the first-order calculation of the orbit-orbit, mutual spin-orbit, and spin-spin interactions, as well as the usual spin-orbit and mutual electrostatic interactions. The multiplet splitting and crystalline field splitting are treated separately according to a least-squares procedure; the standard deviation of the center of gravity of the multiplets is 200 cm—1 without the orbit-orbit interaction and 105 cm—1 with the orbit-orbit interaction. The values of F2, F4, F6, ζ, and α are 305.4, 51.88, 5.321, 729.5, —, cm—1, respectively, in the first case, and 307.9, 50.23, 5.033, 755.1, —0.6542, cm—1, respectively, in the second case. The standard deviation of the calculation for 40 of the crystalline field levels is 7 cm—1. If the deviation of the 1D2 levels, which fit the calculation particularly badly, are not included, the standard deviation is then only 4 cm—1. The values of the crystalline field parameters are: A20 〈r2〉=47.26,A40 〈r4〉=−40.58,A60 〈r6〉=39.62,A66 〈r6〉=26.67 cm−1.
Molecular Structure of Propylene
Authors: Lide David R. , Christensen Daniel
Published: January 2005

The microwave spectra of seven isotopic species of propylene have been studied in order to obtain an accurate molecular structure. The complete rs (substitution) structure has been calculated. The more important parameters are: r(C=C)=1.336±0.004 A,r(C–C)=1.501±0.004 A, ≰CCC=124.3∘±0.3∘. The structure is compared with those of related molecules. It is concluded that no difference can be detected in the double-bond lengths in ethylene, propylene, and the vinyl halides. The CC single-bond length in propylene is indistinguishable from that in acetaldehyde and other acetyl compounds, and is 0.025 A shorter than the CC distance in saturated hydrocarbons. In the =CH2 group in propylene, the CH bond trans to the methyl group appears slightly shorter than the cis CH bond; a similar effect occurs in the vinyl halides.
Electrical Properties of Nonstoichiometric Uranium Dioxide
Authors: Aronson S. , Rulli J. E. , Schaner B. E.
Published: January 2005

Electrical conductivity and thermoelectric power measurements have been made on nonstoichiometric UO2 at temperatures of 500–1150°C. The conductivity data in the single phase UO2+x region can be represented by the equation σ(ohm cm)−1=(3.8×106)/T(2x)(1−2x) exp[(−0.30±0.03 ev)/kT].An approximate equation for the thermoelectric power Q, is Q=(k/e) ln(1−2x/2x).

The electrical measurements confirm the ionic theory of nonstoichiometry in UO2, postulated on the basis of thermodynamic evidence. Nonstoichiometric UO2 is a relatively simple ionic solid in which activated electronic hole transfer occurs between U5+ and U4+ ions in the lattice.
Analysis of the Spectra of Trivalent Promethium and Holmium
Authors: Crozier M. H. , Runciman W. A.
Published: January 2005

The spin-orbit matrices for the f4 configuration have been calculated and checked. These have been applied to the analysis of the solid-state spectra of trivalent promethium and holmium. A tentative energy-level scheme for promethium is obtained. In the case of holmium, all levels below 27 000 cm—1 have been identified, including two levels hitherto unreported in the solid state, at 25 900 cm—1 and 26 190 cm—1, and a root mean-square deviation between calculated and observed energies of 96 cm—1 is achieved. Values of the Landé splitting factor g are predicted for the holmium levels.
Calculations of the Coefficient of Viscosity and the Coefficients of Diffusion for Dissociating Hydrogen
Authors: Clifton David G.
Published: January 2005

The kinetic theory of dilute monatomic gases and mixtures has been used to calculate some transport properties of dissociated hydrogen. The H2–H2 and H–H2 interactions have been assumed to obey the modified Buckingham (exp-6) potential and the Lennard-Jones (12–6) potential, respectively, and the two H–H interaction potentials (1Σg and 3Σu) have been treated by the method of Hirschfelder and Eliason to obtain a weighted average rigid-sphere collision diameter. The coefficient of viscosity, the coefficient of diffusion in a binary mixture of the H–H2 system, and the coefficients of self-diffusion for H atoms and H2 molecules have been computed for temperatures from 1500° to 5000°K and pressures of 0.1, 0.5, 1, 2, 10, 50 and 100 atm.
Optical Absorption Spectra of Ni-Doped Oxide Systems. I
Authors: Pappalardo R. , Wood D. L. , Linares R. C.
Published: January 2005

The optical absorption was studied at room temperature, at 78°, and at 4.2°K in the 2.6-μ to 0.2-μ region in single crystals of MgO, ZnO, MgAl2O4, and yttrium-gallium garnet doped with nickel. The absorptions found were correlated to electronic transitions within the 3d-shell using the formalism of the crystal-field theory. The value of the Dq and B parameters were derived for MgO:Ni (Dq = — 815 cm—1; B = 890 cm—1) and for ZnO:Ni where Ni is tetrahedrally coordinated (Dq = 405 cm—1; B = 795 cm—1). Interesting fine structure was found in the absorption spectra of MgO:Ni and its implications are discussed. An attempt is made to explain some of the fine structure of the absorptions in MgO and ZnO as due to spin-orbit effects. The observed spectra for MgO:Ni are used to infer the presence of Ni++ in octahedral coordination, both in the spinel and in the green phase of yttrium gallium garnet.
Thermal Diffusion Coefficient of Polystyrene in Toluene
Authors: Herren Cecil LeRoy , Ham Joe S.
Published: January 2005

A moving boundary technique is used to measure the thermal diffusion coefficient for polystyrene in toluene as a function of molecular weight. An almost constant value of 1.5×10—7 cm2/mole/deg was obtained except below a molecular weight of 300 000 where a much smaller figure was found. This result agrees with the theory of Ham but disagrees with earlier measurements of Hoffman and Zimm.
Nuclear Magnetic Resonance in CuF2·2H2O Single Crystals
Authors: Shulman R. G. , Wyluda B. J.
Published: January 2005

We have measured the hydrogen and fluorine nuclear magnetic resonance signals in single crystals of CuF2·2H2O. The hyperfine interaction between the fluorine nucleus and the magnetic electrons has been separated into isotropic and anisotropic components which have been evaluated. The Néel temperature has been determined to be 10.92°±0.2°K in contrast to the maximum in the susceptibility which had been shown to occur at 26°K.
Asymmetry of Cyclotron Resonance Lines in the Reaction Zones of Low-Pressure Acetylene and Cyanogen Flames
Authors: Bulewicz E. M. , Padley P. J.
Published: January 2005

A marked asymmetry and shift of line maximum (at 17 000 gauss) by more than 100 gauss is reported for cyclotron resonance lines obtained in or very close to the reaction zones of low-pressure flames containing high concentrations of free electrons. The effect is interpreted in terms of the variation of the real part of the refractive index of the flame plasma, at microwave frequencies, in the neighborhood of the absorption line. The electron concentration gradients in the vicinity of the reaction zone then have the effect of refracting the microwaves traversing the finite thickness of the plasma towards or away from the microwave receiver.
Optically Active Lattice Vibrations as Treated by the GF-Matrix Method
Authors: Shimanouchi Takehiko , Tsuboi Masamichi , miyazawa Tatsuo
Published: January 2005

A general description has been given of an application of the Wilson's GF-matrix method to the treatment of optically active lattice vibrations. As examples, formulas are derived for the calculation of the frequencies of the lattice vibrations of a one-dimensional, the diamond, and CaF2 lattices.
Absolute Infrared Intensity Measurements in Thin Films
Authors: Maeda Shiro , Schatz P. N.
Published: January 2005

A theoretical investigation has been made of the errors which will be incurred if reflection effects (including multiple reflections) are neglected in making absolute (absorption) intensity measurements on thin films of pure liquids and solids. The results are presented in a series of figures for a number of typical experimental situations as a function of two generalized parameters. These figures permit an estimation of the error for any specific case. It is found that the error can be quite appreciable for some experimentally realistic situations. Since a computer program has been written to do the calculations, the authors are willing to run specific cases upon request.
Mutual Diffusion of the Gas Pairs H2–Ne, H2–Ar, and H2–Xe at Different Temperatures
Authors: Paul R. , Srivastava I. B.
Published: January 2005

The mutual diffusion coefficients of H2 with Ne, Ar, and Xe have been determined by the two-bulb technique of Ney and Armistead in the temperature range —30° to 68°C. Diffusion was allowed to take place through a precision capillary tube connecting the two diffusion bulbs and samples of the gas were analyzed at different times with the help of a previously calibrated thermal-conductivity analyzer.

A least-square method was then followed to calculate the force constants on the Lennard-Jones (12:6) potential model from the experimental values of the diffusion coefficients. Also, using experimental values of the mutual-diffusion coefficient, thermal conductivity, and viscosity of pure components, the thermal conductivity of various mixtures were calculated and a good agreement with the experimental data was obtained.
Metallic Nature of the Starch-Iodine Complex
Authors: Bersohn R. , Isenberg I.
Published: January 2005

A weak electron resonance has been observed in the amylose-iodine complex. It is shown that if the iodine atoms in each chain are covalently bonded to each other, the band of the 5pσ states is only partially filled. Hence the row of atoms will have metallic properties including weak paramagnetism and electronic conductivity.
Paramagnetic Resonance of Some Silver (II) Compounds
Authors: McMillan J. A. , Smaller B.
Published: January 2005

The electron paramagnetic resonance of acidic solutions of silver (II) and several silver (II) solid complex compounds has been investigated. In all cases a strong g anistropy permitted the evaluation of the principal g values. In two cases, the hyperfine splitting could be measured without ambiguity. Parallel measurements of the optical and ultraviolet absorption in the case of silver (II) solutions indicated that the hole is not localized on the paramagnetic ion.
Modulation Broadening of Unsaturated Lorentzian Lines
Authors: Wahlquist Hugo
Published: January 2005

Closed, analytic expressions are obtained for the harmonic amplitudes which arise in the modulation of unsaturated Lorentzian absorption lines. Exact formulas relating characteristics of the observed signals (amplitude, width, slope ratios, etc.) to the true half-width for arbitrary modulation amplitude are derived. The results of greatest experimental interest are graphed.
Neutron Diffraction Study of Solid Deuteroammonia
Authors: Reed John W. , Harris P. M.
Published: January 2005

The crystal structure of the stable cubic modification of solid deuteroammonia has been determined by neutron diffraction. The space group is P213—T4, and at —196°C the positions of the atoms are 4N at (a) with u=0.2127±0.0021 and 12D at (b) with x=0.3740±0.0019, y=0.2632±0.0037, and z=0.1094±0.0016. Each nitrogen atom is hydrogen bonded to the six nearest neighbor nitrogen atoms. There is one deuterium atom per site, in contrast to the ``half-hydrogen'' structure of ice. The N—D bond length of 1.005±0.023 A is indistinguishable from that of the free molecule, while the D—N—D bond angle of 110.4°±2.0° is appreciably larger than the free molecule value.
Meaning of the Tait Coefficients and the Structure of Liquids
Authors: Ginell Robert
Published: January 2005

The coefficient L is in the main concerned with the volume of the large clusters. While this volume is positive for clusters of low molecular weight, it becomes small and finally negative as the clusters increase in size. The clusters can increase in size due to a temperature rise or an increase in molecular weight. Hence the value of L goes through a maximum. It is shown that at the critical temperature Pc=—L. Calculations from this relationship give the critical pressure of liquid helium I to be 2.258 atm (experimentally 2.26 atm). This relationship also gives insight into the nature of the critical state. The coefficient J is a function of the change in the fraction of holes with a change in volume at constant temperature. While J appears to be constant with pressure along an isotherm, it is not, however, constant with temperature; it is only a slowly varying function. Various deductions are drawn from the fact that J has almost the same value for groups of related substances. A resume of the structure of liquids in the light of this theory is given.
Vibrational Spectra of Inorganic Molecules. III. Infrared Reflection Spectra of Molten Lithium, Sodium, and Potassium Hydroxides
Authors: Wilmshurst J. K.
Published: January 2005

The infrared reflection spectra of molten lithium, sodium, and potassium hydroxides have been obtained from 4200–200 cm—1 and the optical constants derived by the method of Robinson and Price. The absorption spectra are consistent with some latticelike structure in the liquid state, with the degree of order in the three melts being virtually identical. The hydroxide ion is most probably unassociated and freely rotating in all melts.
Effect of Interstitial Li on the Density of Si
Authors: Prener J. S. , Williams F. E.
Published: January 2005

The densities of silicon and of silicon containing interstitial Li+ were determined. There is a volume expansion of 4.7×10—24 cm3 per Li+ dissolved in silicon. This expansion is interpreted as arising from the Coulombic repulsion between the Li+ and the partially shielded Si4+ cores. Calculations based on a simple model of the charge distribution in silicon are in accord with this interpretation. The density change accompanying the room temperature deionization and aggregation of the lithium was also measured. During the initial stages of this process, the volume increases linearly by 6.0×10—24 cm3 per lithium transferred from the ionized to the deionized state. This expansion is interpreted as arising from overlap repulsive forces between the Si and aggregates of neutral lithium in neighboring interstitial sites. Considerations based on the size of Li0 in these aggregates and the free energy change for the deionization and aggregation process support this interpretation. A final nonlinear region in the observed volume expansion is interpreted as being due to the precipitation of lithium metal so as to leave itself and the silicon strain free.
Polarized Visible Spectra of Crystalline Trisoxalatometallates
Authors: Piper T. S. , Carlin Richard L.
Published: January 2005

The absorption of polarized light by single crystals of NaMgAl(C2O4)3·9H2O with part of the aluminum isomorphously replaced by the trivalent ions of Ti, V, Cr, Mn, Fe, and Co is reported. Assignments of the observed transitions are made. The polarizations prove that both the spin-allowed and spin-forbidden transitions are electric dipolar. They are made allowed by the static asymmetric ligand field and not by coupling to vibrations. The trigonal field strength is evaluated in terms of the parameter K which is found to range from —350 to +500 cm—1.
Measurement of Electrodiffusion. Effect of Electrosmosis on Diffusion
Authors: Scholten P. C. , Mysels Karol J.
Published: January 2005

If a tube containing an electrolyte is subjected to an axial alternating electric field, an oscillating electrosmotic flow will generally occur. The resulting increase in diffusional transport is calculated and compared with the increase in transport due to a simultaneously occurring reaction, i.e., with electrodiffusion. It is shown that for tubes a few millimeters wide electrodiffusion is generally overshadowed by ordinary diffusion and the increase of the latter by electrosmosis. Therefore such systems are not suitable for the determination of reaction rate constants through the measurement of electrodiffusion.
Negative Ion Formation in Ozone
Authors: Curran R. K.
Published: January 2005

Negative ion formation in ozone was studied in a mass spectrometer. Negative ions of O, O2, and O3 were observed. The appearance potentials of O— and O2— are O ev and 0.42±0.03 ev, respectively. The data on O— formation yield D(O2—O)≤1.02±0.15 ev and the data on O2— formation lead to a limiting value for the electron affinity of O2 of EA (O2) ≥0.58 ev.
Markoff Chain Model for Growth of Polymer Single Crystals
Authors: Price Fraser P.
Published: January 2005

A theory is presented wherein the development of a polymer single crystal is envisioned as the successive coherent addition of layers of segments of polymer molecules, each layer acting as the substrate for the succeeding layer. The substrate is assumed smooth and the distribution of segment lengths in the next layer is assumed to be controlled by equilibrium considerations. The theory predicts that as the supercooling is increased the energy gained due to the bulk energy of crystallization tends to overwhelm the energy lost due to formation of new surfaces. This has the result of making the average segment length of the adding layer closer and closer to the substrate length. In some cases it even exceeds the substrate length. The net result is that the temperature dependence of ultimate crystal thickness is not as great as was implied by the (ΔT)—1 laws of previous theories.

The theory has been satisfactorily fitted to the experimentally observed dependence on temperature of single crystals of linear polyethylene grown from dilute xylene solution. The parameters used to fit theory to experiment are a lateral surface energy of 13.3 ergs/cm2, an end (fold surface) energy of 110 ergs/cm2, and a solution temperature of 113°C. The theory also indicates that the surface of the polyethylene crystals is remarkably smooth with an average roughness of only one to two angstroms. Predictions are also made concerning the profile of a single crystal in the region of its primary nucleus (central region). It is shown that hollows, sharp spikes, or flat topped mesas of considerable extent may be observed depending on the supercooling.
s-Tetrazine. I. High-Resolution Vapor-Phase Study of the Visible n→π Vibronic Absorption Band Systems
Authors: Spencer Glenn H. , Cross Paul C. , Wiberg Kenneth B.
Published: January 2005

The low-resolution electronic spectrum of s-tetrazine vapor has been measured down to about 190 mμ, and the complex systems of vibronic bands that comprise the n→π* visible absorption spectrum have been studied under higher resolution. These latter spectra were photoelectrically recorded in the third order of a 21-ft grating spectrograph, using path lengths from 0.05 to 48 m and temperatures from —70° to 70°C. In the absorption region, 4500 to 6100 A, the spectrum consists of over 500 sharp, vibronic band peaks. Their collected Q-branch maxima have been measured to the nearest cm—1, but no discrete rovibronic structure was resolved.

The outstanding feature of the visible spectrum is a set of four intense progressions, each of which is propagated by the consecutive excitation of the same vibration (believed to be the totally symmetric mode 6a). In the ground state, the frequency of this vibration is 737 cm—1 for s-tetrazine-d0 and 720 cm—1 for s-tetrazine-d2; these frequencies drop to about 700 and 690 cm—1, respectively, in the excited n→π* state(s). From simple molecular orbital theory and the Herzberg-Sponer-Teller selection rules, a plausible, preliminary, singlet absorption model is developed and is qualitatively applied to the spectral data. Because there may be an ``almost accidental degeneracy'' of some of the n→π* states of the azines (excluding pyridine), the need for a more elaborate model that will properly treat the electronic-vibrational interaction problem is emphasized. Although a complete vibronic analysis has not yet been obtained, the presence of three electronic transitions forbidden on the basis of D2h excited state molecular symmetry, as well as the electronically allowed n→π* transition, is suspected.
Studies in Molecular Structure. VI. Potential Curve for the Interaction of Two Hydrogen Atoms in the LCAO MO SCF Approximation
Authors: Fraga Serafin , Ransil Bernard J.
Published: January 2005

The LCAO MO SCF method, both in the single-configuration and a limited configuration interaction approximation, has been utilized to evaluate the potential curve of the ground state of H2; wave functions and total molecular energies are presented for a wide range of the internuclear distance (1.0 a.u. ≤R≤18.0 a.u.). These solutions were then used to construct potential curves for the ground states of the molecular ions H2+ and H2— and for the lower-lying excited states of the neutral molecule. Results of vibration-rotation analyses for the stable states are presented. The results for a population analysis of the single-configuration ground-state function over the whole range of R are given, and compared to similar results for He2.
Nickel-Activated Calcium and Strontium Sulfide Phosphors
Authors: Avinor M. , Carmi A. , Weinberger Z.
Published: January 2005

Calcium sulfide activated by nickel and copper or nickel and silver gives an emission band at 680 and 625 mμ, respectively. In strontium sulfide the emission bands appear at 775 and 710 mμ, respectively. The presence of both activators is necessary for the production of these emissions.
Molecular Friction in Dilute Gases. II. Thermal Relaxation of Translational and Rotational Degrees of Freedom
Authors: Sather Norman F. , Dahler John S.
Published: January 2005

Expressions for the rates of equilibration of the translational energies in multicomponent gas mixtures of structureless molecules are derived in terms of characteristic relaxation times. The approach to equilibrium is found to be completely dominated by an exponential decay factor for molecules interacting with inverse power potentials; the decay should be essentially exponential for more realistic potential functions. The calculations of rotational relaxation times are presented for several rigid molecular models: rough and partially rough spheres, spherocylinders, and loaded spheres. The relaxation times obtained are in good agreement with those observed experimentally and with those predicted by previous theories. It is found that, in general, on the order of 10 collisions are required to reduce an initial temperature difference by a factor of 1/e for translational-rotational equilibration.
Optical Absorption Study of Co-Doped Oxide Systems. II
Authors: Pappalardo R. , Wood D. L. , Linares R. C.
Published: January 2005

The optical absorption spectra of several Co-doped oxide systems (MgO, ZnO, aluminum spinel, yttrium gallium garnet, and germanium garnets) have been studied at room temperature, 78°, and 4.2°K, and analyzed using the formalism of the crystal-field theory. Oscillator strengths and cubic-field parameters have been derived. The observed data for tetrahedrally coordinated Co2+ are found to agree satisfactorily with the theoretical predictions. The effect of the spin-orbit coupling on the cubic-field terms has been calculated and the predicted splitting compared with the structure of the absorption bands of MgO:Co and ZnO:Co. The optical absorption properties of MgO:Co and ZnO:Co are used to infer the site symmetry of Co2+ in systems (spinels and garnets) in which the cations occupy sites of different symmetry.
Normal Vibrations and Urey-Bradley Force Constants of Methyl Amine
Authors: Wu Ellen L. , Zerbi Giuseppe , Califano Salvatore , Crawford Bryce
Published: January 2005

Using least-squares fitting to the experimental frequencies, the Urey-Bradley force constants and their uncertainties have been calculated for methyl amine and deuterated derivatives. From the calculation, new assignments of the NH2 twisting vibrations are proposed: CH3NH2, 977 cm-1; CH3ND2, 744 cm-1; CD3NH2, 1078 cm-1; and CD3ND2, 701 cm-1. Potential-energy distributions of these four molecules are reported.
Construction of Reliable Internuclear Potential Curves from Equilibrium Bond Lengths and Vibrational Frequencies
Authors: Steele D. , Lippincott E. R.
Published: January 2005

A method is presented for the construction of reliable internuclear potential curves using a previously proposed function and observed values of equilibrium bond lengths and vibrational frequencies. The function has the form V=De{1−exp[−(nΔr2/2r)]}{1+af(r)}.

An explicit form is presented for the observed periodicity of the parameter a when referring to the ground states of diatomic molecules. This periodicity is shown to lead to relationships from which De, αe, and xeωe can be calculated solely from ωe and re. An empirical relationship between the values of the parameter a in the ground and the excited states is presented from which De, αe, and xeωe can be deduced for any nonionic excited state from ωe and re of that state. This latter relationship demonstrates that ωere2 is not constant for all states of any molecule but is dependent in a predictable manner on the other spectroscopic constants. These relationships enable potential curves to be constructed solely from a knowledge of ωe and re. Calculated curves for the X1Σg+ states of H2 and I2 and ground and excited states of N2 agree extremely well with experimental curves, deviating by no more than 2% of the dissociation energy. The agreement is very good for large values of r for H2 and I2, which indicates that a general form exists for the interaction of bonding atoms at large distances.
Gaseous Diffusion in Porous Media at Uniform Pressure
Authors: Evans R. B. , Watson G. M. , Mason E. A.
Published: January 2005

A model is presented for the diffusion of gases in porous media in the absence of pressure gradients, in which the porous medium is visualized as a collection of uniformly distributed ``dust'' particles which are constrained to be stationary. By formally considering the dust particles as giant molecules, it is possible to derive all the desired results very simply from rigorous kinetic theory as special cases of multicomponent mixtures. By formally varying the mole fractions of the real gas molecules, the entire pressure range from the Knudsen region to the normal diffusion region can be covered. This model permits the first satisfactory theoretical derivation of the experimentally discovered fact that the flux ratio for binary mixtures is equal to (m2/m1)½ at all pressures (not just in the Knudsen region). It also permits a rigorous theoretical treatment of the entire transition region for the first time, from which is obtained the usual Bosanquet interpolation formula and a differential equation for diffusion which covers the entire range (and appears to be new). The model gives no quantitative a priori characterization of the porous medium itself, but if one gas mixture is measured in a given medium, then the behavior of other gas mixtures in the same medium can be predicted.
A High-Resolution Study of CO2 Absorption Spectra between 15 and 18 Microns
Authors: Madden Robert P.
Published: January 2005

A study has been made of the absorption due to individual lines and Q branches of CO2 bands in the 15-to 18-μ spectral region. The strengths and widths of absorption lines on the low-frequency side of the v2 fundamental band and in the 02°0–0110 band of C12O216 have been measured. In the latter band the variation of line strength and width with J has been determined as well as the Coriolis interaction parameter. The strengths of five other bands of C12O216 have been determined from measurements on their Q branches, and the strengths of the v2 fundamental bands of the isotopes C13O216 and O18C12O16 have been estimated. The rotational structure of the v2 fundamental Q branch for C12O216 is partially resolved, and the band constants determined. The v2 fundamental band head of the O18C12O16 isotope is reported.

The spectra were taken in 1956 after construction of the large infrared spectrometer at the Laboratory of Astrophysics and Physical Meteorology, The Johns Hopkins University. This f/6 spectrometer utilizes 3-in. long curved slits and a 14- by 12-in. grating in a Fastie-Ebert mounting. It is demonstrated that this instrument has available an optical slit width of 0.06 cm-1 at 17 μ.
Thermal Conductivity of Polyatomic Gases and Relaxation Phenomena
Authors: Saxena S. C. , Agrawal J. P.
Published: January 2005

Experimental thermal conductivity data for nitrogen, air, carbon dioxide, oxygen, methane, nitric oxide, and hydrogen have been interpreted in terms of Eucken and Hirschfelder theories. The departure from these theories is attributed to the relaxation of internal energy. At present only a qualitative comparison is possible between the information derived here and that obtained from the studies on the propagation of ultrasonic and shock waves. However, it seems possible to develop a quantitative interpretation for carefully planned thermal conductivity data. Only hydrogen shows an anomalous behavior which is attributed to the uncertainties in the experimental data. This view receives confirmation from the data on binary mixtures of inert gases with hydrogen, and also from an analysis of helium.
Recalculation of the Surface Energies of Alkali Halide Crystals
Authors: Benson G. C.
Published: January 2005

Previous calculations of the surface energies of the {100} and {110} faces of alkali halide crystals, including corrections for the relaxation of the outermost layer, have been repeated employing more recent values of the parameters describing the repulsion between the ions. The adoption of the new data overcomes some difficulties formerly encountered in considering the distortion of the surface region.
Raman Spectra of Metal Carbonyl Compounds. III. Raman Spectrum, Vibrational Analysis, and Bond Structure of Nickel Tetracarbonyl
Authors: Stammreich H. , Kawai K. , Sala Osw. , Krumholz P.
Published: January 2005

The Raman spectrum of Ni(CO)4, excited by He-lines 5875.6 and 6678.1 A, has been restudied. A new frequency assignment is proposed, based upon measurements of intensities and the state of polarization of the observed Raman shifts, and taking into account the results previously obtained on the Raman spectra of Fe(CO)5, Fe(CO)42—, and Co(CO)4—. Assuming a simplified quadratic valence force function containing seven potential constants, a normal coordinate analysis has been carried out. The force constants as calculated by means of this model satisfactorily reproduce the observed frequencies. The numerical values of the constants, as compared with those of the isoelectronic anions Co(CO)4— and Fe(CO)42—, provide direct evidence for partial multiple M—C bonding and conjugation between M—C and C–O bonds in metal carbonyl compounds and lead to approximate evaluations of bond numbers.
Raman Spectra of Metal Carbonyl Compounds. IV. Raman Spectra and Structure of Cadmium and Mercury Cobalt Carbonyl
Authors: Stammreich H. , Kawai K. , Sala Osw. , Krumholz P.
Published: January 2005

The complete Raman spectrum of Cd[Co(CO)4]2 and a partial one of Hg[Co(CO)4]2, excited by helium radiation in the red and near infrared spectral range, are reported. A salient feature of the observed spectra is the appearance of an intense, strongly polarized shift at 152 (161) cm—1, not found in the spectra of mononuclear metal carbonyls, that must be assigned to the symmetric Cd(Hg)–Co stretching mode. The results exclude the presence of one or more bridging CO groups in the compounds referred to and point strongly to both the existence of a three-fold principal molecular axis containing the atoms O–C–Co–Cd(Hg)–Co–C–O, and to the staggered D3d configuration of the entire molecule.
Diffusion of Hydrogen in the γ Phase of Titanium Hydride
Authors: Coogan C. K. , Gutowsky H. S.
Published: January 2005

The diffusion of hydrogen in titanium hydride has been examined in terms of a simple electrostatic model. The energy of a hydrogen atom at various positions in the lattice has been calculated from screened Coulombic potentials, neglecting repulsive terms of other origins. This gives Ea, the activation energy for hydrogen diffusion, as a function of the net electronic charge on the hydrogen atom. Agreement with the experimental results for Ea is obtained from a value for the electronic charge on the hydrogen which is consistent with other evidence. The model exhibits the distinct preference of the hydrogen atom for the accommodation in tetrahedral rather than octahedral interstices in the γ phase. It predicts the decrease observed in Ea for titanium hydrides containing less than the stoichiometric proportion of hydrogen. Moreover, the model provides an explanation of the tendency for hydrogen in the γ phase to distribute itself randomly and uniformly throughout the lattice rather than to form aggregates.