bluuebunny/crossref_metadata_2025 huggingface dataset:
Double-Quantum Light Scattering by Molecules
Authors: Bersohn R. , Pao Yoh-Han , Frisch H. L.
Published: January 2005

Double-quantum light scattering by a system of molecules is discussed in this paper. Expressions have been obtained for the scattered light intensity considering both the coherent and incoherent contributions. In that coherent contributions are also considered in this treatment, it goes beyond the scope of previous studies. It is shown that, for molecules of low symmetry, elliptically polarized light must be used in order to determine five independent quadratic forms in the 18 symmetric components (βijk+βikj). According to the present results, the apparent discrepancy between the observed value of ⅓ for the depolarization ratio for CCl4 and the value to be expected from theory may be due to the fact that the coherent contribution had been neglected in previous theoretical considerations. In general, orientational correlation is essential if there is to be appreciable contribution from coherent scattering. For macromolecules, this constitutes a major difference between single- and double-quantum scattering, and additional information may be expected if the latter is investigated experimentally.
Absorption Spectrum of Activated Nitrogen in the 600–1100-Å Region
Authors: Huffman R. E. , Larrabee J. C. , Tanaka Y.
Published: January 2005

Activated nitrogen produced by a microwave discharge has a large number of absorption bands in the 600–1100-Å region in addition to bands of ordinary nitrogen. The present analysis indicates that the additional bands belong to the same band systems as the ordinary nitrogen bands in this region, but the bands are produced by transitions from v>0 levels of the ground state. A brief note concerning the atomic absorption spectrum of nitrogen in the same region is included.
Chemical-Shift Data for Water and Aqueous Solutions
Authors: Rüterjans Heinrich H. , Scheraga Harold A.
Published: January 2005

Since the chemical shift δ of the proton magnetic resonance signal of water can be assumed to be approximately proportional to the degree of hydrogen bonding, xHB, the temperature dependence of the chemical shift is calculated using theoretical values of xHB vs t from various theories of water structure. These theoretical curves of δ are compared to the experimental temperature dependence of the chemical shift.

In addition, the chemical shift of water in some alcohol and carboxylic acid solutions is measured and discussed.
Influence of the Nature of Ionizing Particles on the Specific Luminescence of Organic Scintillators
Authors: Voltz R. , da Silva J. Lopes , Laustriat G. , Coche A.
Published: January 2005

The relationship between the specific luminescence dS/dx of organic scintillators and characteristic quantities of the ionizing particle is investigated. Considering the existence of the two scintillation components and the effect of δ rays, it is shown that dS/dx depends on the specific energy loss dE/dx and on the charge number z of the incident particle: For a given differential energy loss, the ion having the greatest charge number gives rise to the highest light output; for a given particle with increasing dE/dx, the specific luminescence goes through a maximum.

The theoretical conclusions are in agreement with experimental results obtained using α particles of 1 to 8 MeV, 3He ions in the energy range 1–3 MeV and protons from 0.3 to 3 MeV. An experimental device is described, which allows a direct measurement of the energy loss ΔE of particles passing through a thin organic scintillator, and of a quantity proportional to the number ΔS of emitted photons.
Matrix Elements of General Potentials in the Harmonic-Oscillator Representation
Authors: Wilcox R. M.
Published: January 2005

The m, n matrix element of an arbitrary potential function V(q) in the one-dimensional harmonic-oscillator representation is shown to be given by 〈m | V(q) | n〉= ∑ r=0mα(m!n!)12r!(m−r)!(n−r)! ∫ −∞∞dyg(αy)e−12y2(iy)m+n−2r,where α≡(2ω/ℏ)½, and g(αy) is the Fourier transform of V(q). This formula is specialized to the cases where V(q) is given by qj, qje−½γq2, ejαzq, and q−1 sin(αλq), where j is a nonnegative integer and γ, z, and λ are real parameters. Results are compared, where possible, with previous work.
Microwave Rotational Spectrum of Indium Monochloride
Authors: Delvigne G. A. L. , de Wijn H. W.
Published: January 2005

With a high-temperature Stark-spectrometer the J=4←3 rotational spectrum of 115In35Cl has been observed. Quadrupole hyperfine structure has been observed for the lowest four vibrational states. In an analysis of the spectrum the following constants have been derived: the rotational—vibrational constants Y01, Be, Y11(≈—αe), Y21(≈γe), Y02(≈—De), and Y20(≈—ωexe); the quadrupole coupling constants eqQ including the dependence on the vibrational state; the coefficients a0, a1, and a2 of the internuclear potential; and the internuclear distance re. From the quadrupole hyperfine structure it is concluded that the molecule is 77% ionic, and that the antishielding factor of In+—γ∞≈65.
Significant-Structure Theory of Ionic Binary Liquid Mixtures: Potassium Chloride—Potassium Bromide and Sodium Chloride—Sodium Bromide
Authors: Vilcu R. , Misdolea C.
Published: January 2005

The bases of the significant-structure theory are briefly discussed and the theory is applied to the calculation of the excess thermodynamic functions for the binary mixtures KCl–KBr and NaCl–NaBr at constant pressure and temperatures of 1083.16°, 1133.16°, and 1163.16°K. Calculated values are compared with calorimetric data.
Raman Intensity in Binary Solutions
Authors: Wall Theodore T. , Hornig Donald F.
Published: January 2005

Relative to the intensity in pure solvent, the integrated intensity of a Raman band in solution decreases not linearly with molar concentration, but more or less rapidly as the refractive index of the solution rises or falls on addition of solute. This behavior is treated here as a consequence of excited-state interactions between the components of the solution. With hybrid intermediate states in the perturbation-theory expression for the scattering coefficient, the reported correlations between Raman intensities in solution and refractive index or ultraviolet absorption spectra can be derived. In a Drude type of approximation, the lowest-lying pure electronically allowed transition frequency is the only parameter necessary to reproduce the correlations and also to account for the similarity in behavior among the several Raman bands of any species. The temperature dependence of the water stretching band and the lack of large direct cation effects, even in solutions containing colored cations, can also be interpreted. Some of the illumination factors that must be considered before intensities observed in optically dissimilar solutions may be compared are discussed, and the possible analytical uses of Raman intensities are briefly mentioned.
Prediction of Isomeric Form and Bond Angles for Covalent Molecules and Ions
Authors: Searcy Alan W.
Published: January 2005

An electrostatic model for prediction of bond angles in covalent molecules is extended to molecules and ions whose central atoms are surrounded by five or six valence electron pairs of which at least one pair is a lone pair. The stable isomers are the isomers which provide the lone pair electrons with the maximum possible cone of space adjacent to the central atom. Angular deflections from symmetrical coordination positions in these molecules are in the directions predicted by the model, but the observed deflections are usually less than those expected on the basis of behavior in simpler molecules.
Line Intensities in the Raman Effect of 1Σ Diatomic Molecules
Authors: James Thomas C. , Klemperer William
Published: January 2005

The effect of rotation-vibration interaction on line intensities in the Raman effect is examined. Both the rotation-vibration and pure rotation spectra are discussed. It is shown that from a study of relative line intensities one can obtain the quantities β0/β1re and κ12/β12, where β0 and β1 are the first two terms in the expansion of the anisotropy of the polarizability about the equilibrium internuclear distance re, and κ1 is the derivative with respect to internuclear distance of the spherical part of the polarizability. The treatment considers only the case of a harmonic oscillator and is carried through to terms of order γ2, where γ = 2Be/ωe.
Liquid Isochores and Derived Functions of n-C7F16, c-C6F11CF3, c-C4Cl2F6, n-2,2,3C4Cl3F7, CCl2F·CCl2F, and CCl4
Authors: Smith E. Brian , Hildebrand Joel H.
Published: January 2005

Values of the function, (∂P/∂T)v have been determined for six liquids through ranges of 1–60 atmos and initial temperature ranges as high as 25°. The values at 1 atmos and 25°C in atmos deg—1 and the compressibilities×104 calculated from them are, respectively, C7F16 7.10, 2.34; c—C6F11CF3 7.53, 2.18; c—C4Cl2F6 8.61, 1.76; n—C4Cl3F7 8.97, 1.41; CCl2F·CClF2 8.67, 1.50; CCl4 11.22, 1.23.

Since (∂2P/∂T2)v = 0 in the range of the observations, (∂E/∂V)T is a pure volume function, but v2(∂E/∂V), (v is molal volume) is not strictly constant, as it would be for a van der Waals liquid, but the drift is substantially reduced, and the relation between ∂E/∂V and ΔEvap, the energy of vaporization per mole, are both consistent with the relations: vn+1(∂E/∂V)=nvnΔEvap=const with values of n having the following values, in the order of liquids given above: 1.49, 1.44, 1.35, 1.36, 1.19, 1.09.

These relations are explained qualitatively in terms of the expression derived by Hildebrand and Wood for the potential energy of a liquid in terms of its distribution function and intermolecular pair potentials.
H Theorems for One-Dimensional Combustion of a Gas
Authors: Rosen Gerald
Published: January 2005

The equations for unsteady one-dimensional combustion processes are derived under very justifiable physical assumptions. The combustion equations dictate that a functional of the temperature distribution, called H, always decreases with time at an increasing absolute rate. This H theorem is used to determine the critical size of a pocket of gas which can instigate combustion waves. For the case of ``normal'' diffusion, the asymptotic combustion equation implies that a second functional of the temperature distribution, called H*, always decreases with time at a decreasing absolute rate. This second H theorem is associated with a dynamical principle equivalent to the full content of the asymptotic combustion equation.
Proton Magnetic Resonance of the CH3 Group. V. Temperature Dependence of T1 in Several Molecular Crystals
Authors: Stejskal E. O. , Woessner D. E. , Farrar T. C. , Gutowsky H. S.
Published: January 2005

The proton T1 has been observed by rf pulse techniques in acetonitrile, neopentane, t-butyl chloride, 2,2-dichloropropane, and methyl chloroform from their melting points to temperatures about —150°C. Activation energies of 5 to 6 kcal/mole were obtained for self diffusion in the high-temperature solid phase of neopentane, t-butyl chloride, and 2,2-dichloropropane. Activation energies ranging from 1 to 4.5 kcal/mole were obtained for molecular tumbling and from 3 to 4 kcal/mole for CH3 group reorientation in the series of tetrasubstituted methanes, neopentane to methyl chloroform. The effects of intermolecular forces on CH3 group reorientation are shown by the activation energy of 2.1 kcal/mole found for acetonitrile, which has no internal barrier. The various results confirm that a tunneling mechanism is plausible for the CH3 group reorientations.

Other results include: the Bloch decay after a 90° pulse in solid methyl chloroform has a ``slow beat'' which is the Fourier transform of the triplet line shape found in steady-state experiments. The dependence of T1 upon resonance frequency in the low-temperature phase of methyl chloroform exhibits systematic effects attributable to proton-chlorine spin exchange induced by reorientations of the CCl3 group. The T1 is constant in the super-cooled high-temperature solid phase of methyl chloroform. There is an anomalous increase in the T1 at the low-temperature transition in t-butyl chloride, indicating a higher molecular mobility during the phase transition than in either stable solid phase. A 2:1 mixture of CH2DCCl3 and CH3CCl3 gave proton T1 values only 1.3 to 1.6 times as long as those in normal CH3CCl3, whereas the tunneling mechanism suggests a 20-fold increase. Spin exchange between protons in neighboring CH2DCCl3 and CH3CCl3 molecules accounts for the results and it is proposed that spin exchange may be investigated directly by observing T1 in appropriate isotopic mixtures of known composition.
Theory of the Electron Spin Resonance of Benzene in the Triplet State
Authors: Hameka Hendrik F.
Published: January 2005

The splitting of the energy levels of the lowest triplet state of the benzene molecule has been calculated. The splittings were calculated with the aid of first-order perturbation theory from antisymmetrized wave functions, which were composed of linear combinations of Slater orbitals. In the absence of an exterior magnetic field the triplet levels are split as a consequence of the spin-spin interaction, the effect of spin-orbit interaction may be neglected. The result is a doublet and a singlet; the separation of the two levels is 0.15 cm—1 for the 3B1u state and 0.09 cm—1 for the 3B2u state.
Structures of Calcium Dicarbide and Uranium Dicarbide by Neutron Diffraction
Authors: Atoji Masao , Medrud Ronald C.
Published: January 2005

The C–C distances of the C2 groups in calcium dicarbide and uranium dicarbide have been determined by the powder neutron diffraction method. The C–C distance in calcium dicarbide is 1.20±0.01 A, equal to the triple bond C–C distance, but not 1.4 A as reported previously. Uranium dicarbide is isostructural with calcium dicarbide and has the C–C distance of 1.34±0.01 A essentially that of a C–C double bond. The interatomic distances in calcium dicarbide, uranium dicarbide, lanthanum dicarbide, and lanthanum sesquicarbide are discussed in connection with the electronic configuration of the C2 group.
Effect of Pressure on the Absorption Edges of Certain Elements
Authors: Suchan H. L. , Wiederhorn S. , Drickamer H. G.
Published: January 2005

The effect of pressure has been measured on the absorption edges of selenium, arsenic, white phosphorus, red phosphorus, and iodine. In all cases a red shift of the edge (decrease of the energy gap) occurs with increasing pressure. White phosphorus undergoes a transition to the conducting black phase near 30 000 atmos. The change in the gap with pressure for selenium is correctly predicted from conductivity measurements. An extrapolation of the gap to zero indicates that the gaps of these elements will have disappeared below 300 000 atmos. This compares with previous work on sulfur where the estimated pressure for zero gap is 400 000 atmos.
Semiquantitative United-Atom Treatment and the Shape of Triatomic Molecules
Authors: Wulfman Carl E.
Published: January 2005

The united-atom expansion of the potential energy of an electron in a molecular field is transformed into a Maclaurin series expansion containing a remainder term. It is shown that, if the center of nuclear charge is chosen to remain at the origin, the first nonzero terms of this expansion are quadratic in the nuclear separations. These terms determine the orbital properties as the nuclei in the united atom are slightly separated, and are useful in establishing correlation diagrams. Several such diagrams are given for triatomic molecules. The angular derivatives of the quadratic terms are used in an investigation of the angular stability of linear molecules composed of atoms from the second row of the periodic table. It is found that these derivatives themselves correctly indicate the linearity or nonlinearity of all except 26 electron systems, and that the nonlinearity of 26 electron systems is accounted for if internuclear repulsions are taken into account. Extensions and limitations of this result, and its implications with respect to theories of molecular shape are briefly discussed.
Microwave Spectrum and Structure of Propynal (H–C≡C–CHO)
Authors: Costain C. C. , Morton J. R.
Published: January 2005

The moments of inertia IB0 and IC0 of fifteen isotopic species of propynal have been determined from the frequencies of certain lines in the type a spectra. With the aid of type b transitions, IA0 and the inertial defects Δ have been obtained for some of the isotopic species. Using equations relating the atomic coordinates to the change in the moments of inertia on isotopic substitution, three independent sets of molecular parameters have been obtained (two for C=O). The agreement between the three sets of data is within the probable experimental error. The mean values of the molecular parameters are as follows: rs(C–H) (acet.) = 1.0553A, rs(C–H) (ald.) = 1.1064A, rs(C≡C) = 1.2089A, rs(C–C) = 1.4446A, rs(C=O) = 1.2150A, ≰CCO = 123°47′, ≰CCC = 178°24′, ≰CCH (ald.) = 113°54′, ≰CCH (acet.) = 180°0′.

The error in the bond lengths is estimated to be ±0.001 A, and in the angles ±10′. A slight deviation from linearity (1°36′±10′) was apparent in the carbon chain.
Molecular Structure of Ethylene
Authors: Bartell L. S. , Bonham R. A.
Published: January 2005

The structure of gaseous ethylene was investigated by the sector-microphotometer method of electron diffraction. The major internuclear distances, in terms of center of gravity parameters rg(0), were found to be C–H = 1.084±0.003 A, C=C = 1.3327±0.002 A, and C–—H = 2.120±0.006 A, and the angle H–C–H was 115.5±0.6°. Root-mean-square amplitudes of vibration were lC–H = 0.0768±0.003 A, lC=C = 0.0439±0.002 A, and lC–H = 0.102±0.006 A, which values agree reasonably well with values calculated from spectroscopic data. The uncertainties reported represent standard errors computed by a simplified method from least squares analyses of parameters. Discrepancies between the diffraction results and those of new infrared and Raman results are discussed in terms of the arbitrariness arising from the different operational definitions of bond distances and angles involved.
Vibrational Relaxation of Nitric Oxide
Authors: Robben Frank
Published: January 2005

The vibrational relaxation of nitric oxide has been determined in a shock tube with a spectrophotometric technique. The temperature range covered was from 450 to 1300°K, and relaxation times of the order of 5–10 μsec were observed at densities of about 0.07 atmos. From the relaxation times P1–0, the probability of de-excitation from the first vibrational level, was found to be about 8×10—4 at 500°K. Computations of P1–0 made according to the theory of Schwartz, Slawsky, and Herzfeld with an interaction potential derived from viscosity measurements are the order of 2×10—5 times smaller than the experimental values. The use of a potential derived from an (NO2) complex appears to account for the discrepancy.
Experimental Determination of the Oscillator Strength of the First Negative Bands of N2+
Authors: Bennett R. G. , Dalby F. W.
Published: January 2005

The radiative lifetime of the upper state of the 3914 A transition of N2+ was measured to be (6.58±0.35) 10—8 sec, corresponding to an oscillator strength f of (3.48±0.20) 10—2. The apparent radiative lifetime of the upper state of the 3371 A transition of the second positive system of N2 was found to depend upon the conditions of excitation. Extrapolation to excitation threshold yields a lifetime of (4.45±0.6) 10—8 sec.
Studies in Molecular Dynamics. I. General Method
Authors: Alder B. J. , Wainwright T. E.
Published: January 2005

A method is outlined by which it is possible to calculate exactly the behavior of several hundred interacting classical particles. The study of this many-body problem is carried out by an electronic computer which solves numerically the simultaneous equations of motion. The limitations of this numerical scheme are enumerated and the important steps in making the program efficient on the computers are indicated. The applicability of this method to the solution of many problems in both equilibrium and nonequilibrium statistical mechanics is discussed.
Electron Diffraction Investigation of Triphenylamine
Authors: Sasaki Yasushi , Kimura Katsumi , Kubo Masaji
Published: January 2005

The molecular structure of triphenylamine in the gaseous state was determined by means of the sector-microphotometer method in electron diffraction. Some useful information on bond lengths and valency angles was obtained by resolving the radial distribution curve, on the basis of which a more detailed interpretation of the molecular intensity was made with the comparison between experimental and theoretical intensity curves. Some features in the intensity curves were found to be sensitive to changes in the angle ∠CNC and the twist angle φ of phenyl groups about their respective principal axes from the position in which the threefold axis of symmetry lies on the plane of each phenyl group. The experimental intensity data were adequately interpreted in terms of a nonplanar model having C3 symmetry. A planar structure was definitely ruled out by the present analysis. Probable values for the molecular parameters adjusted by the method of least squares are: r(C–C) = 1.392±0.006 A, r(C–N) = 1.42±0.04 A, ∠CNC = 116°±2°, and φ = 47°±5°.
Dielectric Properties of Polypeptide Solutions. IV. Several Problems on the Electric Dipole Moment of the α-Helix
Authors: Wada Akiyoshi
Published: January 2005

Relating to the dielectric properties of the α-helical molecule described in a previous report, the following problems have been studied from the standpoint of the confirmed structure of this molecule.

1. The electric dipole moment of the α-helix has been estimated considering the dipole moment in the side chain besides that in the backbone chain.

2. The dielectric constant of the solution of α-helices has been obtained in terms of the dipole moment and polarizability of the solute molecules. The reaction field, which will be induced in such a cylindrical molecule immersed in the dielectric media, has also been examined.

3. It was found that the deviation of the observed dielectric dispersion and absorption curve from Debye's theoretical one of single relaxation time could satisfactorily be explained when the polydispersity of the molecular weight was taken into account.
Fine Structure of the Cl2 Quadrupole Resonance Spectrum
Authors: Douglass Dean C.
Published: January 2005

Calculations are made which indicate that the observed splitting of the Cl2 quadrupole resonance spectrum arises from isotope effects on the thermal motions of the Cl2 molecules. The type of motion considered is a torsional oscillation of the molecules about their centers of gravity.
Kinetics and Mechanism of Ethylene Oxide Decomposition at High Temperatures
Authors: Crocco L. , Glassman I. , Smith I. E.
Published: January 2005

In a new flow reactor designed for the study of reaction kinetics at high temperatures, the rates of decomposition of ethylene oxide were measured to temperatures approaching its adiabatic decomposition point (∼1200°K). This device is unique in that it follows the reaction process, not by a freezing technique usually employed in flow systems, but by tracing the temperature history of the reaction.

The ethylene oxide decomposition study showed that the kinetics followed an over-all first-order mechanism and the over-all activation energy was 42±2 kcal/mole. The results were found to be independent of the amount of fuel injected, the velocity of the inert carrier gas, and the inert gas itself. A free radical decomposition mechanism consistent with the experimental results is postulated.
Debye θ of Hexagonal Crystals at 0°K
Authors: Wolcott Norman M.
Published: January 2005

A set of numerical tables is given which permits the easy calculation of the Debye characteristic temperature at 0°K of any crystal with hexagonal symmetry. The use of the tables presupposes a knowledge of the elastic constants, atomic volume, and density of the crystal. Values of the characteristic temperature obtained with the use of the tables are compared with those obtained by direct calculation in a number of special cases.
Dipole Moment Function of CO(1Σ+)
Authors: Salwen Harold , Trischka John
Published: January 2005

The possible dipole moment functions of CO(1Σ+) are calculated by means of the wave function approximation with wave functions for a Morse potential. The dipole moment functions are expressed as polynomials whose coefficients through the quartic terms are given in a table. The accuracy of the dipole moment functions is discussed for the case in which only the first two vibrational matrix elements are known. This discussion is based on calculations made by both the wave function approximation and an older method, the polynomial approximation. A Morse potential and a polynomial potential are compared to determine their relative suitability for the calculation of the dipole moment function of CO(1Σ+).
Molecular and Crystal Structure of B8Cl8. I. Preliminary X-Ray Diffraction Study
Authors: Atoji Masao , Lipscomb William N.
Published: January 2005

Unit cell dimensions and space groups of two modifications of B8Cl8 are described. The density measurements indicate that the formula hitherto represented as (BCl0.9)x is in best agreement with B8Cl8. Complete three-dimensional x-ray diffraction data of one of the modifications have been taken. The unit cell of this form is orthorhombic, of symmetry P212121 and four B8Cl8 molecules in a unit cell of dimensions a=13.64, b=7.85, and c=12.91 A.
Nonresonant Microwave Absorption and Electric Dipole Moment of NO in the Gaseous State
Authors: Maryott A. A. , Kryder S. J.
Published: January 2005

The microwave absorption in NO has been measured by a resonant cavity method at frequencies near 9 and 23 kMc/sec and at pressures in the range 3 to 27 atmos. The major part of the absorption is due to direct Λ-type doublet transitions, although at the higher pressures, a significant contribution also comes from the low frequency wings of the pure rotational spectrum. Since the Λ-doublet separation is much smaller than the applied frequency for all significant transitions, the resulting spectrum has the nonresonant or Debye shape. From the intensity of this spectrum, the electric dipole moment was found to be 0.148±0.002 debye. The effective collision cross section for random spacial reorientation of the molecules is approximately twice the kinetic collision cross section.
Kinetics of Coordinate Bond Formation. III. Method of Temperature Patterns and the Reaction NH3+BF3
Authors: Smith F. T. , Kistiakowsky G. B.
Published: January 2005

The method for determining rate constants from the temperature pattern in dilute spherical diffusion flames is critically examined, and several possible sources of error are corrected for. The method is tested by a re-examination of the reaction NH3+BF3 over a wide range of experimental parameters. On the whole, previous results are confirmed, but the high-pressure limiting rate is found to be 1.2×1011 cm3/mole-sec, somewhat less than half of the former value, and some new quantities can be measured. Ammonia is found to be about 3 times as effective as nitrogen in energy-exchange collisions with the excited product of the initial addition reaction. In the absence of N2, the rate constant is ½ the high-pressure limit when the NH3 concentration is about 8×10—8 mole/cm3. The heat of the gas-phase addition reaction is 27.5±2 kcal/mole and the equilibrium constant for the reverse reaction is ≪2×10—10 mole/cm3. The activation energy, if any, is less than 3 kcal/mole.
Oscillator Strengths in the Far Ultraviolet. I. Nitric Oxide
Authors: Bethke George W.
Published: January 2005

Absolute integrated absorption intensities have been measured for the nitric oxide beta, gamma, delta, and epsilon bands in the range 1700 to 2300 A. From these data the electronic absorption oscillator strengths of the beta and gamma band systems have been calculated to be 0.00151±7% and 0.00240±5%, respectively. The experimental method involved the photometric detection of pressure broadened nitric oxide spectra. Also described is the construction of a logarithmic load resistance which allows the direct tracing of spectra in absorbance units.
Rapid Procedure for Rigorous Analysis of Electron Diffraction Data
Authors: Bonham R. A. , Bartell L. S.
Published: January 2005

A refined procedure for the analysis of electron diffraction patterns of gas molecules has been developed and programed for rapid computation by the IBM 650 digital computer. In addition to increasing greatly the speed and accuracy of data processing, it reduces to routine practicability the most rigorous methods of structural analysis presently available. Improved methods for handling standard electron diffraction computations and several new schemes facilitating molecular structure determinations are given including an objective determination of parameters by the method of steepest ascents. A simplified means of estimating standard errors is developed.
Absorption Spectrum of Manganous Fluoride
Authors: Stout J. W.
Published: January 2005

The absorption spectrum of single crystal MnF2 has been measured in the range 2700–6000 A. In the room temperature axial spectrum peaks are observed which are identified with transitions from the 6A1g(6S) ground level to various quartet levels. The wave numbers in units of 103 cm—1 corresponding to transitions to the various levels are: 4T1g(4G), 19.44; 4T2g(4G), 23.5; 4A1g(4G), 25.19; 4Eg(4G), 25.50; 4T2g(4D), 28.12 and 28.37; 4Eg(4D), 30.23; 4T1g(4P), 33.06. The spectrum is interpreted in terms of a perturbation of the free ion energy levels by an octahedral ligand field including the diminution of the magnitude of the dγ orbitals on the Mn++ ion by a factor (1 — ε)½ in calculating the coulomb and exchange integrals. ε is the ``covalency parameter'' of Koide and Pryce. Energy matrices in the strong field representation and the free-ion representation are calculated. The spectra are fitted with ε = 0.064 and the octahedral ligand field parameter Dq = 0.78×103 cm—1. From measurements of the π and σ spectra with polarized light it is concluded that the transitions are electric dipole ones. The spectra were also photographed with a grating spectrograph at temperatures down to 20°K. At 20°K sharp lines are seen corresponding to the transitions to the 4A1g(4G), 4T2g(4D), and 4Eg(4D) levels. A shift of about 0.06×103 cm—1 in the transition to the 4A1g level between 77° and 20°K is in agreement with that expected from the effect on the energy levels of the antiferromagnetic ordering energy.
Effects of Crystalline Defects on Pure Quadrupole Resonances
Authors: Randall J. L. , Moulton W. G. , Ard W. B.
Published: January 2005

The line width and second moment of the Cl35 pure quadrupole line have been measured as functions of x-irradiation time and inhomogeneous compression in sodium chlorate, potassium chlorate, and p-dichlorobenzene. The effect of the addition of p-dibromobenzene to p-dichlorobenzene has also been studied. In all cases an increase in the line width and second moment was observed, and in a few cases, a decrease in the integrated intensity was found. Several broadening mechanisms have been considered in detail, and it has been concluded that strain broadening is probably the predominant mechanism in all cases.
Interactions between Oxygen and Nitrogen: O–N, O–N2, and O2–N2
Authors: Vanderslice Joseph T. , Mason Edward A. , Maisch William G.
Published: January 2005

Potential energy curves for O–N interactions corresponding to the X 2Π1/2,X 2Π3/2,A 2Σ+,B 2Π,C 2Π,D 2Σ+,E 2Σ+, and B′ 2Δ states of nitric oxide have been calculated from spectroscopic data by the Rydberg-Klein-Rees method. Curves for the 4Π, 2Σ, 4Σ, 6Σ, and 6Π states have been obtained from limited spectroscopic results and from relations derived from approximate quantum-mechanical calculations. Two semi-independent calculations have been made, and are in good agreement with each other. The quantum-mechanical relations also lead to approximate curves for the O–N2 and O2–N2 interactions over a limited range. The O2–N2 interaction is consistent with one valid at larger separation distances which has been derived from high-temperature gas viscosity data.
Exploratory Study, by Low-Temperature X-Ray Diffraction Techniques, of Diborane and the Products of a Microwave Discharge in Diborane
Authors: Bolz L. H. , Mauer F. A. , Peiser H. S.
Published: January 2005

It has been suggested that atomic hydrogen may form a loose, one-electron bond with stable electron-deficient molecules such as diborane (B2H6). Such bonding might make possible the stabilization of quasi-atomic hydrogen at higher temperatures or in higher concentrations than have been attained previously. To test this theory, diborane and the products of a microwave discharge in diborane have been studied by x-ray diffraction in the temperature range 4.2° to 100°K.

Two structurally related phases have been distinguished in ordinary diborane. The low temperature or α phase is formed by deposition from the gas at 4.2°K. It transforms slowly to β diborane above 60°K. The β phase is also obtained by depositing at 77°K and annealing above 90°K to eliminate traces of the α phase.

An additional phase is found in specimens formed by freezing at 4.2°K the products of a microwave discharge in diborane. It is probably a boron-hydrogen compound with a triple-point temperature of about 60°K. It may be BH3. This compound is not known definitely, but some evidence for its existence has been reported.

In each experiment with ``discharged'' diborane, warm-up began with a sudden increase in temperature from 4.2° to about 33°K while there was still helium in the Dewar. The source of heat has been traced to hydrogen frozen out with diborane and other products of the microwave discharge. The temperature rise, which may have been initiated by a process such as recombination of atomic hydrogen trapped in the solid, was sustained by heat transferred from the Dewar walls by hydrogen gas released from the sample.

Since the heat release occurred spontaneously at a temperature near 4.2°K it cannot be concluded that diborane helped appreciably to stabilize atomic hydrogen in the solid.
Collision Theory of the Kinetics of Dissociation of Diatomic Molecules
Authors: Widom B.
Published: January 2005

A collision theory is developed for the rate of dissociation of diatomic molecules dilutely dispersed in an inert gas, the theory being identical in its basic structure to the collision theory of Rice but differing from the latter in some of its details. The rate constant is found to be κ=c(μ12A12/ℏr02)Zexp(−D/kT),where Z is the collision number, D the dissociation energy, μ the reduced mass of the diatomic molecule, r0 its equilibrium internuclear distance, A the magnitude of the coefficient of the attractive r—6 term in the long-range interaction energy of its two atoms of its diatomic molecule, and c a dimensionless constant estimated to be 0.27.
Thermodynamic Functions of Some Gaseous Diatomic Halides of Aluminum, Boron, and Lithium
Authors: Altman Robert L.
Published: January 2005

A literature survey was made to locate spectroscopic data on the gaseous halides of aluminum, boron, and lithium. The thermodynamic functions were computed and a tabulation of the heat capacity, enthalpy, and entropy of the gaseous diatomic bromides, chlorides, and fluorides of aluminum, boron, and lithium has been made from zero to 6000°K in order that this useful thermodynamic information may be available.
Bond Energies and the Interactions between Next-Nearest Neighbors. I. Saturated Hydrocarbons, Diamond, Sulfanes, S8, and Organic Sulfur Compounds
Authors: Allen Thomas L.
Published: January 2005

Interaction energies of atoms which are next-nearest neighbors have been determined from thermodynamic data for a number of carbon and sulfur molecules. When these interactions are taken into account, bond energies are found to be constant to a high degree of precision.

Additional factors which have been considered include thermal and zero-point energies, interactions of more distant neighbors, trigonal interactions, and ring strain.Simple equations for the prediction of unknown heats of formation are developed.
Infrared Spectra of Trimethylborane-d9 and Triethylborane-d15
Authors: Lehmann W. J. , Wilson C. O. , Shapiro I.
Published: January 2005

The infrared spectra of B(CD3)3 and B(C2D5)3 are reported in the 2 to 15 μ range. After minor revisions of a previous frequency assignment for B(CH3)3, the force constants obtained from a modified valence force treatment of B(CH3)3 have been used to calculate and assign the frequencies of B(CD3)3. This assignment is consistent with frequency values predicted from a study of other methyl-deuterated compounds. Agreement with the Teller-Redlich product rule is fair. An interesting and perhaps unexpected feature is the upward shift of the B–C asymmetric stretching frequency upon deuteration; the correctness of the assignment of that vibration was verified by use of B10(CD3)3. In the latter part of this article, the observed bands of B(C2D5)3 are assigned.
Dislocation Type Defects in Glass
Authors: Levengood W. C. , Vong T. S.
Published: January 2005

Flaws formed on freshly broken surfaces of glass reacted to various types of applied stress in a manner suggestive of dislocation type defects. Localized shear stresses caused existing defects to disappear and created new flaws which formed a cyclic pattern between parallel scratches made on newly created surfaces. These flaws formed behind the scratching tool and appeared to be associated with harmonically moving stress waves in the glass. Thermally induced stress energies were also found to increase the probability of flaw formation.

Matching flaws were produced by nonuniform cohesional forces between internal crack surfaces. This effect was interpreted as the result of limited moisture penetration causing zones of reaction products and localized stress concentrations. The morphology of the defects indicated a dislocation within the glass which produced slip lines on the surface. The critical shear stress found to affect the flaws was determined by loading with spherical indenters.
Molecular Dissociation and Reconstitution on Solids
Authors: Ehrlich Gert
Published: January 2005

The dependence of heterogeneous reactions on the nature of the solid surface is explored by analyzing the elementary rate processes involved. The relations between the rates of adsorption, surface diffusion, and evaporation, and the depth and distribution of binding sites on the surface are presented. Empirical generalizations concerning the binding energy of adatoms and the cohesive energy of solids are examined; Pauling's additivity rule is found to fail for most metal hydrides and thus does not provide a reliable base for estimating the covalent contribution to the heat of adsorption.

Rates of association of atoms and dissociation of molecules on solids are estimated from a knowledge of the experimental heat of adsorption — ΔH and the postulate that the activated complex for dissociative chemisorption of a diatom has a configuration resembling two noninteracting atoms, one in its equilibrium binding position on the surface, the other in the saddle-point position for surface migration. For chemisorption on clean metals, it is found that an activation energy can be expected only for systems in which the heat of adsorption is small (— ΔH <10 kcal/mole), in agreement with experiment. Conversely, desorption of diatoms by combination of atoms deposited in excess of the equilibrium amounts on metals on which — ΔH <0 is limited only by surface diffusion and therefore should occur rapidly, as is observed.

The mechanism of heterogeneous recombination of atoms is outlined; it is shown that for hydrogen atoms only small variations in the efficiency of this process on different metals are expected at pressures of the monatomic gas less than 10—3 mm, and that these are primarily dictated by the rate of direct recombination between gas phase and adsorbed atoms. For metals on which chemisorption from the molecular gas is endothermic, the recombination coefficient should approach unity above room temperature. In the converse process, the dissociation of diatomic molecules into atoms at a hot metal surface, variations in the rate of atomization may occur for different metals; for those on which adsorption is endothermic the rate should be small since it is the adsorption step which results in specificity. The rate of atomization is also shown to depend upon the first power of the pressure of the molecular gas p2 in the region of low pressures, changing to a dependence on p2½ at higher pressures where encounters between adsorbed atoms become limiting.

The same picture of the activated complex for chemisorption is applied to the interaction of gases with nonmetals. From the appreciable activation energy observed for adsorption of diatoms on nonmetals, it is concluded that binding sites on these surfaces are widely separated. This suggests that dissociation or excitation of the gas-phase molecule to a higher vibrational state should increase the rate of adsorption, and conversely that the recombination efficiency of nonmetals for atoms should be small. These expectations are found to be in agreement with experiment.
Infrared Absorption Spectrum of Lithium Hydroxide
Authors: Wickersheim Kenneth A.
Published: January 2005

The polarized infrared absorption spectrum of crystalline lithium hydroxide in the region between 2500 cm—1 and 8000 cm—1 has been obtained with a grating spectrometer. The spectrum consists in part of a strong band at 3678 cm—1 polarized parallel to the c axis and bracketed in a nearly symmetric manner by five pairs of side bands polarized perpendicular to the c axis and by two pairs of side bands polarized parallel to the c axis. In addition an isolated band at 7172 cm—1 is observed polarized parallel to the c axis. Changes in the spectrum as the sample temperature is increased from room temperature to 400°C are described.

The hydrogen positions in lithium hydroxide have been deduced. It is shown, using the factor group selection rules as a guide, that the spectrum can be explained as consisting of an infrared active OH stretching fundamental surrounded by binary combinations of lattice fundamentals with the infrared and Raman OH fundamentals. The band at 7172 cm—1 is assigned as the binary combination of the two OH fundamentals. The vibrational modes of the crystal belonging to irreducible representations of the factor group have been constructed to within a good approximation. Tentative assignments of deduced lattice frequencies to constructed modes are presented. The present explanation of the lithium hydroxide spectrum is contrasted with the rotation-vibration explanation of Hexter.
Microwave Spectrum, Internal Barrier, Structure, Conformation, and Dipole Moment of Acetyl Fluoride
Authors: Pierce Louis , Krisher Lawrence C.
Published: January 2005

The microwave spectra of eight isotopic species of acetyl fluoride are reported. Interaction of internal and over-all rotation splits the rotational lines into doublets. From the doublet separations of CH3COF the height of the threefold (sinusoidal) barrier to internal rotation was calculated to be 1041 cal/mole. Splittings in the spectra of C13H3COF, CH3CO18F, and CD3COF gave barriers of 1041, 1055, and 1031 cal/mole, respectively.

With the assumption of a symmetrical methyl group, the following structural parameters were determined from the observed rotational constants: C–C1.503 ACCF110∘18′C–F1.348CCO128∘21′C–O1.181HCH109∘30′C–H1.084If the requirement of methyl group symmetry is dropped, the best fit to all the data is obtained with the following methyl group parameters: In−plane hydrogenOut−of−plane hydrogensC–H1.082 A1.096 ACCH110∘24′108∘48′HCH110∘51′107∘16′The observed rotational constants of CH2DCOF and CHD2COF were found to require the H(in-plane)-F trans-equilibrium conformation.

From Stark effect measurements on CH3COF and CH3CO18F the dipole moment was calculated to be 2.96 D. The dipole moment makes an angle of 9°30′ with the C–C bond axis and is directed toward the oxygen atom.
Microwave Spectrum of Acetyl Cyanide
Authors: Krisher Lawrence C. , Wilson E. Bright
Published: January 2005

The microwave spectra of eight isotopic species of acetyl cyanide have been investigated in the region 8000 to 34 000 Mc. The hindered internal rotation of the methyl group splits some of the rotational lines into doublets. Analysis of these splittings for four isotopic species gives a barrier to internal rotation of 1270±30 cal/mole.

From the rotational constants of CH3COCN, C13H3COCN, CH3COC13N, CH3CO18CN, CD3COCN, and CD3C13OCN the following structural parameters were determined: C–H1.086±0.005 A∠HCH108∘44′±30′C=O1.226±0.005∠CmethylCO124∘3′±1∘C≡N1.164±0.005∠CCC114∘59′±1∘Cmethyl–Ccarbonyl1.490±0.010∠CCN180∘ (assumed)Ccarbonyl–Ccyanide1.466±0.010.A study of CH2DCOCN and CHD2COCN shows that in its equilibrium configuration, the acetyl cyanide molecule has a methyl hydrogen opposite the oxygen atom.

A dipole moment of 3.45D was obtained from Stark effect measurements.
On an Approximate Theory of Transport in Dense Media
Authors: Rice Stuart A. , Kirkwood John G.
Published: January 2005

A new approximate theory of transport is presented which starts from the general statistical mechanical theory of heat flux and the stress tensor and uses three principal approximations. These are (a) the expansion of the gradient of the pair interaction potential between molecules at time t+s about the gradient at time t and the neglect of all terms higher than the second, (b) the use of a local equilibrium distribution function in pair-space, and (c) the approximation of the pair diffusion tensor as the direct sum of singlet diffusion tensors. The intermolecular force contributions to the shear viscosity, bulk viscosity, and thermal conductivity are related to equilibrium properties of the fluid and, respectively, to other coefficients of the set of transport coefficients. Absolute calculations for liquid argon are within a factor of two of experiment. A semiempirical calculation suggested by the theory and using the observed diffusion coefficient is in exact agreement with experiment. The validity of the three approximations is discussed.
Growth Mechanism of Copper Whiskers by Hydrogen Reduction of Cuprous Iodide
Authors: Morelock C. R. , Sears G. W.
Published: January 2005

A study has been made of the growth of copper whiskers by hydrogen reduction of cuprous iodide. Alternative mechanisms have been proposed involving, respectively, vapor phase reduction and reduction at the whisker tip. A necessary consequence of the vapor phase reduction mechanism is the presence of a highly supersaturated copper vapor. It is shown that the vapor phase is not highly supersaturated in copper vapor and that reduction must occur heterogeneously. It is further shown that the reduction process occurs only at the tip and is most simply accounted for by assuming reduction at the step associated with an axial dislocation.
Low-Temperature Heat Capacity of Azurite
Authors: Forstat H. , Taylor G. , King B. R.
Published: January 2005

The heat capacity of azurite, Cu3(CO3)2(OH)2, has been measured in the temperature range of 1.7–3.6°K. The characteristic λ-type heat capacity anomaly associated with the antiferromagnetic-paramagnetic transition in the crystal has been observed, the Néel point being 1.84°K. The entropy change associated with this transition has been found to be 1.17 cal/deg mole and agrees fairly well with the theoretical value of 1.38 cal/deg mole calculated from R ln (2S+1). The contribution to this entropy change above the Néel temperature was approximately 35%, which indicates a comparatively slow diminution of the short-range ordering of the Cu++ spins.
Paramagnetic Resonance of F Centers in Potassium Iodide
Authors: Noble Gordon A.
Published: January 2005

The electron-spin resonance of F centers in potassium iodide is observed at 293°K, 77°K, and 4°K. Additively-colored crystals of several concentrations and x-rayed crystals show the same resonance with g = 1.970 and a width of 213 gauss at maximum slope. The saturation of the absorption is measured. The resonances of F centers in potassium halides are compared.