bluuebunny/crossref_metadata_2025 huggingface dataset:
Interpretation of the Infrared Spectrum of a Molecular Crystal: Naphthalene
Authors: Pimentel George C. , McClellan A. L. , Person Willis B. , Schnepp Otto
Published: April 2005

A critical examination of the oriented gas model is made on the basis of several suggested criteria applied to the infrared studies of solid C10H8 and C10D8. The frequency difference between gas and solid spectra is as high as 1 percent ν for only a few naphthalene bands. The dichroic band splittings which can be assigned to intermolecular interactions are small, averaging less than 3 cm—1, but with a few well defined exceptions. A comparison between the observed and predicted dichroic behaviors for those bands whose symmetry classes are known indicates that the dichroism is dominated by the gas phase symmetries of the vibrational modes. The general applicability of the oriented gas model for naphthalene indicates its usefulness in interpreting those solid spectra. On the other hand, the occasional, distinct deviations from the model warn that it is not likely to be useful in studying crystals involving stronger crystal forces (such as hydrogen bonds or ionic forces).
Vibrational Spectra and Assignment of Naphthalene and Naphthalene-d-8
Authors: Lippincott Ellis R. , O'Reilly Edward J.
Published: April 2005

Infrared and Raman spectra taken of samples of naphthalene-d-8 of high deuterium content are reported. These spectra along with spectral data on naphthalene have been used to make an assignment of frequencies to the normal modes of vibration for this molecule. Although this assignment represents a significant contribution towards a correct one and provides good agreement with the experimental thermodynamic data, it still contains a number of tenuous points.
Nuclear Quadrupole Interaction in HCN and DCN in the Bending Vibrational Mode
Authors: White Robert L.
Published: April 2005

The ΔJ=0, ΔF=0 transition in HCN and DCN in an excited bending mode of vibration was observed to possess structure due to an asymmetry in the electric field gradient at the nitrogen nucleus coupling to the quadrupole moment of that nucleus. A selective breaking of the π bond perpendicular to the plane of bending when the molecule assumes its ionic structure is suggested as the source of the asymmetry.
Theoretical Evaluation of Atomic Polarizations of Diatomic Molecules
Authors: Altshuller A. P.
Published: April 2005

The atomic polarizations, PA (theor.), of five diatomic molecules, HCl, DCl, HBr, NO, and CO, have been calculated from an equation derived from dispersion theory (Van Vleck, 1927), using recent data obtained from infrared dispersion and absorption intensity measurements. These PA (theor.) values are compared with the PA (exp.) values obtained from dielectric constant and optical refractive index measurements. The greater accuracy of the PA (theor.) values is emphasized. The PA (theor.) values have been used to recalculate the dipole moments, μ, of the diatomic molecules considered. A qualitative relationship is discussed between the series of dμ/dr and μ values for some of the diatomic molecules. The PA (theor.) are calculated approximately for the gaseous alkali halides.
Relative Diameter of Oxygen and Hydrogen Molecules, using Negative Pressure as an Indicator
Authors: Briggs Lyman J.
Published: April 2005

A vertical glass tube (1 cm bore and about 100 cm long) carries at its closed upper end two opposed spherical platinum electrodes, approximately 1 and 2 mm in diameter. The lower end of the tube is bent upward in the form of a J, to which is attached a cylindrical reservoir. After introducing sufficient electrolyte (1NH2SO4) to more than fill the long tube, the system is evacuated and sealed off.

On rotating the long tube from an inverted to a vertical position, the column of liquid remains hanging from the top of the tube, under a negative pressure (at the top), equal to the length of the column down to the meniscus, times its density, less the vapor pressure in the reservoir. The minimum electric charge required to drop the column is determined by successive trials, using a mica capacitor (adjustable in steps of 0.001 μf), which is first charged to a known potential and then connected to the electrodes through a quick-acting switch. After each drop of the column, the polarity is reversed. Hydrogen is deposited as an incomplete monomolecular film when the smaller test electrode is the cathode; oxygen, when it is the anode.

The critical anodic charge was divided by 2, oxygen being bivalent. The ratio of the critical charges gives the relative number of molecules involved; and its reciprocal, the ratio of the projected areas. The mean of 9 series of measurements gave 1.022±0.006 as the ratio of the diameter of the oxygen to the hydrogen molecule. Measurements by other methods range from 1.54 to 0.89.
A Theory of Thermal Diffusion in Liquids
Authors: Dougherty E. L. , Drickamer H. G.
Published: April 2005

A theory of thermal diffusion in liquids has been developed based on Denbigh's interpretation of the ``net heat of transport'' which arises in the thermodynamics of irreversible processes. The thermal diffusion ratio α is expressed in terms of the energies of vaporization of the pure components, the excess energy, entropy and volume of mixing, and the concentration dependence of ΔUc. The efficiency with which the two species pack together is also introduced. The Hildebrand-Scatchard solution theory is applied to these results and α is expressed in terms of solubility parameters, molal volumes and packing efficiencies.

The equations are compared with previously published experimental results, and reasonably explainable packing efficiencies are obtained.

In the appendices the effects of nonrandomness of mixing are considered and the theory is extended to ternary mixtures.
Free Electron Theory, Finite Differences, and LCAO Molecular Orbitals
Authors: Frost Arthur A.
Published: April 2005

Simpson first called attention to the analogy between the free electron method in finite difference form and the simple LCAO molecular orbital method for electronic energy calculation. This analogy is extended to branched molecules using both the one- and two-dimensional viewpoints and also applied to a case of two electrons in interaction. It appears that the success of the free electron method is due to this similarity to the LCAO method.
Infrared and Raman Spectra of Fluorinated Ethanes. VIII. Pentafluoroethane
Authors: Nielsen J. Rud , Claassen Howard H. , Moran Norma B.
Published: April 2005

The infrared spectrum of gaseous CF3CF2H has been observed in the region from 2 to 38μ, and the spectrum of the liquid at — 50°C from 2 to 22μ, with the aid of LiF, NaCl, KBr, and KRS-5 prisms. The Raman spectrum of gaseous CF3CF2H has been photographed with a three-prism glass spectrograph of linear dispersion 15 A/mm at 4358 A. All but one of the fundamental vibration frequencies have been assigned, and the spectra have been interpreted in detail.
The Kinetics of Coordinate Bond Formation. II
Authors: Kistiakowsky G. B. , Williams R.
Published: April 2005

The technique of temperature pattern determination, shown previously to be suitable for the measurement of fast gaseous reactions, has been extended to reactions of boron trifluoride with ammonia, dimethylamine, n-butylamine, t-butylamine, and pyridine. The bimolecular rate constants of the first two of these show pressure dependence; those of the other three, within experimental error, do not. A comparison with the previously obtained results on methylamine and trimethylamine demonstrates that the lifetime of the ``hot'' quasi-molecules formed by the addition of boron trifluoride and an amine increases regularly with the number of vibrational degrees of freedom of the quasi molecule. The rates of addition are all substantially smaller than the rate of recombination of methyl radicals. They increase by about a factor of thirty from that of ammonia to those of heavier amines, being then about 1/30 of the collisional frequency. This finding is not consistent with the supposition that steric requirements alone limit the rates of addition and the existence of a small activation energy is clearly suggested, although it could not be observed experimentally. To explain the present results, the activation energy must decrease from ammonia to heavier amines. Such a decrease is found to be consistent with the presently accepted views on the electronic structure of the boron-nitrogen bond.
The Determination of Particle Size and Refractive Index Near the Turbidity Maximum in Monodisperse Suspensions of Spherical Particles
Authors: Heller Wilfried
Published: April 2005

Theoretical values on the specific turbidity of colloidal spheres within the range of diameters of 1 to 2 microns are given. It is shown how an unambiguous particle size can be determined within this range in spite of a turbidity maximum. The latter can be determined for almost any refractive index by means of an empirical equation. An alternate turbidity maximum can be used for determining the refractive index of the light scattering material provided the diameter is known.
Energy Calculations for the Linear H3+ Ion System*
Authors: Barker Roland S. , Giddings J. Calvin , Eyring Henry
Published: April 2005

A study of the dependence of the energy calculations for the linear triatomic hydrogen ion system H3, on a single polarization (electron cloud displacement) parameter g, and on two effective orbital charge parameters Z0 and Zm is presented. The studies, with separate screening parameters for the central and outer atomic orbitals, used normalized approximate integrals. The individual variation of Z0, the charge associated with the outer orbitals, and of Zm, the charge associated with the central orbital, gave little improvement of the energy calculation. From these results with approximate integrals, calculations, at this time, using the exact integrals appear unprofitable.

Only exact integrals are used in the study dealing with the off-center electron cloud parameter, g. These exact integral calculations led to an energy of — 158.07 kcal/mole which is 2.74 kcal/mole better than the best previously obtained value for this linear system.
Vibrational Spectra, Force Constants, and Calculated Thermodynamic Properties of Methyltrifluorosilane
Authors: Collins R. L. , Nielsen J. Rud
Published: April 2005

The infrared spectrum of gaseous H3C–SiF3 has been obtained in the region 2.5—36μ. The Raman spectrum of the liquid phase under pressure has been photographed with a three-prism glass spectrograph of linear dispersion 15 A/mm at 4358 A, and qualitative polarization measurements have been made. The eleven active fundamental vibration frequencies have been assigned, and a tentative value has been assigned to the inactive fundamental. A normal coordinate analysis has been made, and thermodynamic properties have been calculated.
Monte Carlo Calculation of the Average Extension of Molecular Chains
Authors: Rosenbluth Marshall N. , Rosenbluth Arianna W.
Published: April 2005

The behavior of chains of very many molecules is investigated by solving a restricted random walk problem on a cubic lattice in three dimensions and a square lattice in two dimensions. In the Monte Carlo calculation a large number of chains are generated at random, subject to the restrictions of no crossing or doubling back, to give the average extension of the chain 〈R2〉Av as a function of N, the number of links in the chain. A system of weights is used in order that all possible allowed chains are counted equally. Results for the true random walk problem without weights are obtained also.
Configuration Interaction Applied to the Hydrogen Molecule
Authors: Callen Earl
Published: April 2005

The electronic wave function for the hydrogen molecule has been described as a sum of three configurations, each of which is expressed in terms of one-electron symmetry orbitals, which are written as variational functions of the elliptic coordinates. To a state due to Coulson, made up of orbitals which are individually even under inversion, we first added an odd-odd state, thus improving the computed binding energy from 3.535 ev to 4.125 ev. The addition of a third state, of a somewhat different character, increases the binding energy to 4.276 ev. The experimentally observed binding energy is 4.72 ev. The role of the several configurations is explained in terms of the concept of spatial correlation, following the work of Lennard-Jones and co-workers.
Absorption Spectrum of NaNO3 Exposed to Ionizing Radiation
Authors: Pringsheim P.
Published: April 2005

The changes produced by ionizing radiation in the absorption spectrum of NaNO3 crystals are in the main caused by two effects: the conversion of NO3— ions into NO2— ions with an absorption band, which has its peak at 345 mμ and shows a characteristic structure when observed at low temperature; and the production of color centers with a continuous absorption band with peak at 335 mμ. The formation of the color centers is assumed to be connected with the presence in the lattice of NO2— ions, although no precise model can be proposed for these centers. The color center band can be bleached by ultraviolet light even at — 190°C; at room temperature it is partially destroyed by the ionizing radiation which is able to produce the centers, while this is not the case with respect to the NO2— ions. Therefore the NO2— band is relatively much stronger in crystals exposed to the ionizing radiation at higher temperatures, for instance in the pile, while in crystals x-rayed at — 190°C the color center band prevails.
Radial Distribution Function Calculated by the Monte-Carlo Method for a Hard Sphere Fluid
Authors: Alder B. J. , Frankel S. P. , Lewinson V. A.
Published: April 2005

The radial distribution function of a fluid of rigid spheres has been calculated using IBM equipment by a Monte-Carlo method which is valid only at relatively low densities. Up to the highest densities studied, 20 percent of closest packing, the radial distribution function agrees within the precision of the method with the one calculated by the use of the superposition approximation in triplet space. Another Monte-Carlo approach was used at a higher density, 72.4 percent of closest packing, and the results agree with published computations.
Molecular Structure and Vibrational Spectra of Ethyl Cyanide
Authors: Duncan Norman E. , Janz George J.
Published: April 2005

The infrared spectra for the gaseous and liquid states, and the Raman spectra for the liquid state, including intensity and polarization data, are reported for ethyl cyanide (C2H5CN). A normal coordinate treatment has been made for four planar and five nonplanar skeletal vibrational modes. The observed spectra are in accord with a C8 model for this molecule. A complete assignment of frequencies to the fundamental modes of vibration is made for ethyl cyanide. From the spectroscopic data, the height of the barrier hindering internal rotation is estimated to be 5200 cal. The thermodynamic functions for ethyl cyanide have been calculated to 1000°K.
On Intermolecular Forces and the Crystal Structures of the Rare Gases
Authors: Jansen John , Dawson Laurens M.
Published: April 2005

The relation between the intermolecular potential field and the stability of crystal structures of the rare gases is investigated for a face-centered cubic lattice and a structure of hexagonal closest packing. Two models of the potential field are used: a Lennard-Jones (s,6) potential and a ``modified'' Buckingham potential (α,6). The effect of zero-point energy is taken into account on the basis of Corner's method. It is found that for an addititive Lennard Jones (s,6) potential (s between 7 and 16) the hexagonal structure is the stable one. For an additive Buckingham potential (α,6), with α varying from 10 to 16, the hexagonal lattice is again more stable than the cubic structure. For both forms of the potential field considered in the analysis, the differences in energy between the two structures is of the order of one ten-thousandth of the cohesive energies of the crystals. These results agree with the conclusions reached by Kihara and Koba, who neglected the influence of zero-point energy. It is known from experiments that neon, argon, krypton, and xenon crystallize in the face-centered cubic lattice. Therefore, if additivity of intermolecular forces is assumed, the results indicate that neither the Lennard Jones nor a modified Buckingham potential can explain the crystal structures of the rare gases except helium. The possible importance of many-body interactions is discussed.
Substituted Methanes. XXIII. Infrared Spectral Data, Rotational Constants, Normal Coordinate Treatments, and Thermodynamic Properties for CD3Br and CH3Br
Authors: Weissman Herman B. , Bernstein Richard B. , Rosser Shirley E. , Meister Arnold G. , Cleveland Forrest F.
Published: April 2005

Infrared spectra were obtained between 400 and 4000 K with NaCl and KBr prisms. The a1 fundamentals for CD3Br are 2157, 993, and 578 K; for CH3Br they are 2972, 1305, and 611 K. For CD3Br, a least squares analysis of the observed wave numbers of the sub-bands of σ6(e) gave for B1,A1,ζ, and σ0 the values 0.255 K, 2.529 K, 0.150, and 712.3 K; for σ5(e) the values were 0.257 K, 2.530 K, —0.339, and 1056.2 K. For σ4(e)=2293 K, the sub-bands were not resolved, but the sum rule gave ζ4=0.240. The microwave value of B0 was used. The signs of B1—B0 for σ6 and σ5 are the same as those previously obtained for CH3I by use of the high-dispersion records of Lagemann and Nielsen. For CH3Br, a least squares analysis of the grating data of Bennett and Meyer gave for σ6(e) : 0.315 K, 5.144 K, 0.217, and 955.4 K; for σ5(e) : 0.304 K, 5.062 K, —0.242, and 1448.2 K; and for σ4(e) : 0.321 K, 5.153 K, 0.064, and 3055.6 K. The sign of B1—B0 for σ6 is the same as for CH3I, but the signs for σ5 and σ4 are reversed. This inconsistency is presumably due to the limited accuracy with which the two small constants B1—B0 and (A1—B1) — (A0—B0) can be determined by the least squares method. The most probable values of the band origins are believed to be, 954.5, 1443.8, and 3056.7 for CH3Br and 711.6 and 1056.4 K for CD3Br (σ4 was not resolved, so no band origin could be obtained). Values of the principal potential constants are: fb=2.8631 md/A, fh=5.1199 md/A, fhh=0.53535 md A/rad2, and fbh=0.62871 md A/rad2. Values are given for 13 interaction constants. For CD3Br, the values of (H0—E00)/T, — (F0—E00)/T, S0, and Cp0 at 100, 273.16, 298.16, 900, and 1550°K are, respectively : 7.95, 42.66, 50.61, 8.00; 8.75, 50.86, 59.61, 11.07; 8.98, 51.63, 60.61, 11.68; 14.23, 64.09, 78.32, 20.38; and 17.57, 72.74, 90.31, 23.44 cal deg—1 mole—1. For CH3Br, the corresponding values are : 7.95, 41.41, 49.36, 7.97, 8.37, 49.51, 57.88, 9.72; 8.50, 50.25, 58.75, 10.14; 12.63, 61.51, 74.14, 18.19; and 15.87, 69.25, 85.12, and 22.00. Values for 27 other temperatures in this range are given.
Thermodynamic Properties of Nitrogen Trifluoride from 12°K to Its Boiling Point. The Entropy from Molecular and Spectroscopic Data
Authors: Pierce Louis , Pace E. L.
Published: April 2005

The heat capacity of nitrogen trifluoride has been measured from 12° to 144°K. The heat of the transition at 56.62°K was found to be 361.8 cal/mole. The heat of fusion at the triple point temperature, 66.37°K, was found to be 95.1 cal/mole. The heat of vaporization at the normal boiling point, 144.15°K, was found to be 2769 cal/mole. The vapor pressure has been measured, and the data are closely represented by the equation log10Pmm=−673.5828/T+1.869858 log10T−0.00783355T+4.64615.The entropy of nitrogen trifluoride gas has been calculated from the calorimetric data and the third law of thermodynamics to be 54.50 cal/deg/mole at 144.15°K. This value agrees very well with the value 54.61 calculated from spectroscopic data and structural parameters which include a pyramidal model for the molecule.
Vapor Absorption Spectra of Light and Heavy Naphthalenes at 2900—2500 A
Authors: Sponer H. , Cooper C. D.
Published: April 2005

The 2900—2500 A region of absorption in both light and heavy naphthalene is interpreted as an allowed A1g–B2u transition, and the bands at 35 910 and 36 040 cm—1 are assigned as the respective 0,0 bands. Upper-state frequencies of 485, 710, 995, 1390, 1520, and 1600 cm—1 and the ground-state frequencies of 495, 755, 1024, and 1380 cm—1 in the ordinary naphthalene spectrum are correlated with previously reported Raman frequencies. A corresponding interpretation is given for the vibrational frequencies occurring in the spectrum of deuterated naphthalene. The general appearance of the spectrum is compared with recent absorption curves in solid solution by Passerini and Ross, and with crystal data obtained with polarized light. Possible occurrence of vibrationally induced ``forbidden'' bands is discussed.
Self-Diffusion of Carbon Tetrachloride, Isobars and Isochores
Authors: Watts H. , Alder B. J. , Hildebrand J. H.
Published: April 2005

The self-diffusion coefficient of CCl4 has been measured over a range of temperature between 25° and 50°C and at 1 and 200 atmospheres. The results can be expressed by the equations: for 1 atmos, D=325 exp (—3300/RT), for 200 atmos, D=264 exp (—3300/RT). The activation energy for constant volume is 1070 Cal. These activation energies are identical with those previously found for the diffusion of I2 in CCl4. The temperature coefficient of diffusion at constant volume parallels in both cases the increase of kinetic energy. Dη/T is constant within 7 percent in the range studied, where η denotes viscosity. These results are discussed in relation to various theories for the mechanism of diffusion.
Infrared Spectrum and the Structure of the Low-Temperature Phases of Crystalline HCl, HBr, and HI
Authors: Hornig D. F. , Osberg W. E.
Published: April 2005

The infrared spectra of crystalline HCl, HBr, and HI have been studied at —205°C. The fundamental vibrations were observed in HCl at 2704 and 2746 cm—1, in HBr at 2404 and 2438 cm—1, and in HI at 2120 cm—1. In addition, low-frequency bands associated with torsional lattice vibrations were observed directly and in combination with the fundamental vibrations of the molecules. It is concluded that in the low-temperature crystalline phases both HCl and HBr form zigzag hydrogen-bonded chains, the angle between adjacent molecules being about 107° in HCl and 97° in HBr. The crystalline potential function is investigated for all three molecules.
An LCAO MO Study of the Structure of Chlorophyll Prototypes
Authors: Matlow Sheldon L.
Published: April 2005

By means of Wheland's method of treating systems with hetero-atoms three possible isomers of porphyrin and five of dihydroporphyrin are studied from the viewpoint of the energies of the ground states and the transition energies to the lowest lying excited states. In the case of porphyrin it is found that, within the limits of accuracy of the method used, two of the structures, PA (porphyrin-adjacently bonded hydrogens) and PO (porphyrin-oppositely bonded hydrogens), have identical ground state energies. In the case of dihydroporphyrin the DHP-AI (DHP-A—dihydroporphyrin-adjacently bonded hydrogens) isomer is most stable and the DHP-AII and DHP-OII (DHP-O—dihydroporphyrin-oppositely bonded hydrogens) isomers are more energetic by 1.06 and 1.20 kcal/mole, respectively. With respect to the transition energies and the resulting spectra it is possible that the peaks in the spectrum of porphyrin are not due mainly to vibrational fine structure of a single electronic transition, as is proposed by Rabinowitch, but rather are the combination of the electronic spectra of the PA and PO isomers. The dihydroporphyrin spectral analysis, however, indicates that several of the peaks are probably vibrational fine structure of a single electronic transition. The calculated bond orders are given for the various structures discussed.
On the Structure of a Detonation Front
Authors: Gilkerson W. R. , Davidson Norman
Published: April 2005

An effort was made to observe the structure of the reaction zone for a detonation in a gas. Detonations in a 50 percent H2:50 percent O2 mixture at 0.035 atmos pressure containing 1 percent I2 were initiated by shock waves in a shock tube. Because of ignition delays and the short length of tube available, the detonations did not settle down to a steady state and were of unexpectedly high velocity. The iodine served as a colorimetric indicator for the shock front. The light output of the detonation is a step function of time with a front coincident with the shock front within 2—3 μsec. The experiment indicates that the reaction zone is less than 104 collisions thick. A crude theoretical estimate of the reaction zone thickness of 1000—4000 collisions is made. Possible chain initiating steps are also considered.
Potential at Zero Charge for Reversible and Ideal Polarized Electrodes
Authors: Rüetschi Paul , Delahay Paul
Published: April 2005

The potential at zero charge for an ideal polarized electrode, as measured with respect to some reference electrode, varies linearly with the work function of the metal, while this potential for a reversible electrode is independent of the nature of the electrode. This observation is verified experimentally for Ag, Cd, Cu, Ga, Hg, Ni, Pb, Pt, and Tl in the case of ideal polarized electrodes and for Ag, Au, Bi, Cu, Hg, and Pt for reversible electrodes. It is shown that the difference between the Volta potentials from electrode to solution for an ideal polarized electrode at zero charge is approximately —0.33 volt, and that the difference between the Galvani potentials is equal to the surface potential of the electrode. The difference of Volta potentials for a reversible electrode at zero charge varies linearly with the electronic work function of the metal.
Substituted Methanes. XXI. Calculated and Observed Wave Numbers, and Calculated Thermodynamic Properties, for Bromodeuteromethane and Bromodideuteromethane
Authors: Dowling Jerome M.
Published: April 2005

Using potential energy constants obtained from CH3Br and CD3Br, wave numbers (fundamentals) for CH2DBr and CHD2Br were calculated by means of the Wilson FG matrix method with a potential energy function containing all possible second degree terms. The calculated values of the wave numbers were then used to assign existing infrared and Raman spectral data for these molecules. Then the heat content, free energy, entropy, and heat capacity for the ideal gaseous state at 1 atmos pressure were calculated for 12 temperatures from 100 to 1000°K with a rigid rotator, harmonic oscillator approximation.
Cl35 Pure Quadrupole Resonances in Acid Chlorides and Chlorates
Authors: Bray P. J.
Published: April 2005

The pure quadrupole resonances of Cl35 in acid chlorides of some aliphatic dicarboxylic acids have been observed. No resonances have been found in acid chlorides of aliphatic monocarboxylic acids which retain the unsubstituted CH3 configuration at the chain end not occupied by the COCl group. This absence of resonances is attributed to possible randomness in the crystal structure or thermally activated low-frequency reorientations of groups within the molecule.

Resonances have also been measured in several chlorates, sulfuryl chloride, iodine monochloride, iodine trichloride, and selenium tetrachloride. Structural and bonding discussions are given for the latter two compounds.
Substituted Methanes. XXII. Infrared Spectra of CHBrF2, and Potential Constants and Calculated Thermodynamic Properties of CHBrF2 and CDBrF2
Authors: Palm Ann , Voelz Fred L. , Meister Arnold G.
Published: April 2005

The near infrared spectrum of gaseous bromodifluoromethane was obtained using a Perkin-Elmer Model 21 Spectrometer equipped with a NaCl prism. A set of potential constants was determined for CHBrF2 by means of the Wilson FG matrix method, using a potential energy function with all possible second degree terms. The same potential constants were used to calculate the fundamentals of CDBrF2. Finally the heat content, free energy, entropy, and heat capacity were calculated for 12 temperatures from 100 to 1000°K, for the ideal gaseous state at 1 atmos pressure, using the observed fundamentals for CHBrF2 and the calculated ones for CDBrF2.
Dissociation by Impacts of the Second Kind
Authors: Groth W. E. , Oldenberg O.
Published: April 2005

The process by which an excited Kr atom in an impact of the second kind dissociates an N2 molecule is investigated by comparison with related processes. (1) The production of free N atoms is not due to an atom transfer reaction. (2) It is not due to the ``resonance'' transfer of electronic energy of Kr′ directly into vibrational energy of N2 leading to dissociation. (3) It is due to the transfer of electronic energy of Kr′ into electronic energy of N2. The simplest interpretation is the production of a repulsive level of N2 which immediately dissociates.
Interaction of Methylene Deformation Frequencies in Paraffin Crystals II. A Theoretical Treatment of the Interaction of Vibrations
Authors: Stein Richard S.
Published: April 2005

The splitting of the methylene deformation frequencies in crystals of n-paraffins is described in terms of interaction between nearest-neighbor molecules On the basis of a simplified model, the order of magnitude of the splitting may be accounted for Polarization behavior and changes occurring upon heating, cooling, and deuteration are described in terms of this model.
Energy Transfer by Collisions in Vapors of Chlorinated Methanes
Authors: Sette D. , Busala A. , Hubbard J. C.
Published: April 2005

Ultrasonic velocity has been measured at 30°C in the four chlorinated methanes: methyl chloride, methylene chloride, chloroform, and carbon tetrachloride, at pressures from 1.5 cm Hg to more than one atmos in the case of methyl chloride, and with the others to the vapor pressures available up to 28°C and at frequencies from 0.2 to 2 Mc sec—1. Dispersion of the velocity has been found in each case, the relaxation frequency/pressure ratios, correcting for departure from the ideal gas law, at 30° being in CH3Cl, CHCl3, and CCl4 respectively 1.13, 27.3, and 23.3 Mc sec—1 atmos—1. In CH2Cl2 two relaxations have been found with respective frequency/pressure ratios after similar corrections of 2.27 and 105 Mc sec—1 atmos—1.
Dipole Velocity and Dipole Length Matrix Elements in π Electron Systems and Configuration Interaction
Authors: Wolfsberg Max
Published: April 2005

Equations relating dipole velocity and dipole length matrix elements have been tested for π electron systems treated by a molecular orbital method. Considerable improvement in the validity of the equations is noted when configuration interaction is included in the calculations.
Experimental Determination of the Thickness of Weak Shock Fronts in Liquids
Authors: Flook W. M. , Hornig D. F.
Published: April 2005

The thickness of weak shock fronts, across which the pressure difference was in the vicinity of ten atmospheres, was measured by the reflectivity method in acetone, ethyl alcohol, and ethyl ether. They are all of the order of 10—4 cm thick. Lower limits to the thickness were established in water, carbon tetrachloride, benzene, and ethylene glycol. A theoretical expression for the thickness is derived. Comparison between theory and experiment suggests that the effective viscosity in the shock front is several times the ordinary shear viscosity in ethyl ether and acetone but agrees well in ethyl alcohol.
Counter-Ion Distribution in Dilute Solutions of Rigid Spherical Macromolecular Ions in the Absence of Added Salt
Authors: Fujita Hiroshi
Published: April 2005

The electrostatic potential field and the accompanying counter-ion distribution in dilute solutions of rigid spherical-polyelectrolyte ions in the absence of added salt is calculated on the basis of an approximate Poisson-Boltzmann equation. The exact Poisson-Boltzmann equation is approximated so that its characteristic nonlinearity is conserved properly, and the nonlinear equation thus obtained is solved rigorously under relevant boundary conditions. The calculated results reveal a strong tendency of the counter-ions to cluster near the macro-ion, and this occurs even at such extremely low concentrations of the solution as would be beyond the limit of experimental investigation. It is shown that the zeroth-order approximation (in which the basic equation is linear) gives unexpectedly good solutions for the potential distribution even at a fairly high degree of ionization of the macro-ion, but leads to incorrect results for the counter-ion distribution except at a very low degree of ionization.
Nitrogen Afterglow in a Magnetic Field
Authors: Kane Walter R. , Clark K. C.
Published: April 2005

The effect of a magnetic field on the simple exponential decay of a nitrogen afterglow at 0.017 mm pressure is reported. During the afterglow a magnetic field of 850 gauss parallel to the tube axis was alternately present and absent in 95 successive tests; the effect of the field was to slow the decay rate of 0.061 milli-second, as recorded by photomultiplier and oscillograph, by 2.9±0.5 percent. Kinetic theory calculations of the effect, based on plausible assumptions concerning ambipolar diffusion, thermalization of electrons, and electron attachment, are in approximate agreement with the observation, if one considers that ionic recombination provides much of the excitation energy for this short afterglow. An absence of the magnetic effect would be expected if ions played no role in the optical excitation.
High-Speed Machine Computation of Ideal Gas Thermodynamic Functions. II. The Diatomic Free Radicals of the Isotopic Hydrides of Oxygen and Sulfur
Authors: Haar Lester , Friedman A. S.
Published: April 2005

The partition functions for the free radicals are obtained in closed form. They include terms to account for the special low-temperature effects arising with these molecules. The splitting of the 2π ground state is complicated by the uncoupling of the electronic spin from the nuclear axis. In addition to this effect the partition function includes first-order corrections for rotation-vibration coupling, rotational stretching, and vibrational anharmonicity. Tables of thermal functions are computed on the NBS Eastern Automatic Computer—SEAC—from 50° to 5000°K for OH, OD, OT, SH, SD, and ST.
Ultrasonic Absorption in Sugar Solutions
Authors: Verma G. S.
Published: April 2005

Ultrasonic absorption and the frequency at which maximum absorption is to be expected have been calculated in solutions of sucrose, glucose, and lactose at various concentrations and temperatures on the basis of structural changes in the quasi-crystalline structure of the liquid medium. The relaxation frequencies for sugar solutions lie just beyond the ordinary experimental range (∼100 Mcs).
O – O Bond Dissociation Energies in Propionyl and Butyryl Peroxides
Authors: Rembaum A. , Szwarc M.
Published: April 2005

The kinetics of the decomposition of gaseous propionyl and butyryl peroxides was studied in a flow system. It was found that both compounds decompose in a unimolecular manner. The rate constant for the decomposition of propionyl peroxide is given by the equation k=2.5·1014·exp(−30 000/RT),and that for butyryl peroxide by the equation k=1.9·1014·exp(−29 600/RT).It is concluded that D(C2H5·CO·O−O·CO·C2H5)≃D(C3H7·CO·O−O·CO·C3H7)≃30·kcal/mole.The fates of the ethyl and propyl radicals produced in the decomposition are discussed.
Calculation of the Dipole Moment of the Carbon-Hydrogen Bond in Methane by the Thomas-Fermi Method
Authors: Glazer Herbert , Reiss Howard
Published: April 2005

To compute the dipole moment of the CH bond in methane, the pyramids formed by the planes bisecting the HCH bond angles were taken as elements of symmetry. Each pyramid encloses a carbon-hydrogen bond and the four close-pack to form the methane molecule. To symplify the problem, the pyramid was replaced by a cone of equal volume. The Thomas-Fermi equation was solved for the potential within this cone subject to the appropriate boundary conditions, on the IBM Type 701 electronic data processing machines, using the extrapolated Liebmann method. Boundaries were chosen about each nucleus on which the superposition solution was used. The equation was solved for carbon alone and then for carbon-hydrogen within the cone. The dipole moment was taken as the difference between the two in accordance with views recently expressed by Shull and by Coulson. The value obtained was 2.8D C+H—. The large magnitude is attributed to the poor description of the system by the statistical theory.
Linear Association in Nonaqueous Solutions
Authors: Ginell Robert , Shurgan Joel
Published: April 2005

The two-constant theory of linear association has been considered further, and methods have been derived whereby the constants can be evaluated from experimental data. These methods have been applied to data on phenanthrene solutions in ethanol. The agreement of the derived curve with experimental points is excellent. The experimental data go up to ∼3 molal solutions (∼65 wt percent soln.).
Studies of the Interaction between Stable Molecules and Atoms. II. Interaction between Two He Atoms
Authors: Griffing Virginia , Wehner J. F.
Published: April 2005

The repulsive energy of two helium atoms has been calculated using molecular orbital theory. The equations of Roothaan were used to break down the energy into integrals involving atomic orbitals. The necessary integrals are tabulated in the literature for a wide range of parameter which enabled the potential energy curve to be calculated from R=0.6 to 7.0 a0. The Slater (1s) orbital with effective nuclear charge Z=27/16 was used. The potential curve is lower at all distances from those of other investigators in the range where Van der Waals forces give attraction although the curves agree at closer distances. Ionization energies have been calculated over these distances and extrapolated to infinity to give a value which is much better than that calculated with the same orbital by ordinary means. The addition of 2pσ character to the molecular orbitals by constructing hybrid orbitals of the type N {(1s)+λ(2pσ)} and the determination of λ by a SCF calculation according to the scheme of Roothaan, gives an attractive energy of 2.14×10—5 a.u. with λ=1.4×10—3 at R=3.11 A. Experimental values are approximately 3×10—5 a.u. The calculated results are compared with experimental data in the exchange and Van der Waals region of the values of the internuclear parameter.
Vibrational Spectra of Molecules and Complex Ions in Crystals. VIII. The Infrared Spectrum of a Mixed Crystal of 1-Deutero-Ammonia and 2-Deutero-Ammonia
Authors: Reding F. P. , Hornig D. F.
Published: April 2005

The infrared spectrum of a mixed crystal containing NH3, NH2D, ND2H, and ND3 was observed at —190°C. All of the fundamental frequencies of NH2D and ND2H were assigned. A calculation of the 12 frequencies of these two molecules was made, using the four nonzero force constants previously obtained from NH3 and ND3. The average deviation from the observed frequencies was 0.6 percent and the maximum deviation 1.6 percent. It is shown that the coupling between the motions of the various molecules can be neglected.
Method of Calculating Cross Sections for Molecular Collisions
Authors: Bauer Ernest
Published: April 2005

The calculation of cross sections for slow inelastic collisions of molecules, such as occur in chemical reactions, shows an interesting combination of classical and quantum-mechanical features. The de Broglie wavelength is small compared with the range of the intermolecular potential so that there exists a relatively well-defined quasi-classical orbit; but in some cases the coupling constant is small compared with unity, and this gives the problem certain quantum-mechanical characteristics. On account of the condition relating to the de Broglie wavelength, a calculation of the total collision cross section requires the knowledge of the partial waves for a large number of values of the angular momentum lh/.

A method is devised to suit these different features. The WKB method lends itself well to this application, with a quasi-classical amplitude and a quantum-mechanical phase for the wave function. We also use the concept of an impact parameter b rather than the orbital quantum number l: this is well suited to describing a quasi-classical orbit, and hence for calculating the total cross section in a case like the present one. As an example of the method, the cross section for excitation of the first vibrational state of a hydrogen molecule resulting from collision with another hydrogen molecule is calculated.
Resistance in a Liquid-Liquid Interface. III. The Effect of Molecular Properties
Authors: Sinfelt J. H. , Drickamer H. G.
Published: April 2005

The diffusion of molecular sulfur across a saturated liquid-liquid interface has been investigated for several molecular pairs, using a method previously described. The interfacial resistance does not directly depend on polarity of the liquids, nor can it be correlated with interfacial tension. High resistances are associated with liquids which show a high degree of hydrogen bonding. With suitable assumptions it is possible to calculate a free energy of activation for transfer across the interface. It appears that transfer in systems involving negligible resistance is analogous to van der Waals adsorption, while for systems involving high resistance the process is comparable to chemisorption.
Color Centers in Alkali Halides Containing NO2— Ions in Small Concentration
Authors: Hutchinson E. , Pringsheim P.
Published: April 2005

Alkali halide single crystals (KBr, KCl, NaBr, and NaCl) containing NO2— ions at various concentrations, from 0.5 to 0.007 mole percent, were grown by the Kyropoulos method. At high NO2— concentrations the typical NO2— band appears in the absorption spectrum with peak wavelengths between 280 and 260 mμ depending on the nature of the base material. The production of F-bands by exposure to x-rays is completely suppressed in these crystals at room temperature and greatly inhibited at —190°C. Instead of the F-band, a continuous band (C-band) is produced with a wavelength nearly coincident with the NO2— band, but not showing at low temperature the vibrational structure characteristic of the latter. Other less important new absorption bands appear in the red and the ultraviolet. At lower NO2— concentrations F-bands begin to appear in competition with the C-bands. The bleaching of the various absorption bands by light absorbed in them is investigated and discussed. NaCl seems to differ from the other halides in so far as in this crystal the production of the F-band is greatly enhanced by NO2— in concentrations which in KBr greatly inhibit the formation of F-centers.
Collision Excitation of Molecular Vibrations in Halogen-Substituted Methanes
Authors: Rossing Thomas D. , Legvold Sam
Published: April 2005

Departures from the equilibrium between vibrational and translational energies in gases are characterized by relaxation times which depend upon the ease with which vibrations may be excited or de-excited by collisions. The de-excitation process has been discussed by various authors on the basis of the relative velocity of approach of two colliding molecules and on the basis of the relative energy of approach.

The dispersion of ultrasound has been measured in fourteen halogen-substituted methanes and compared with existing data. Binary collisions were found to be responsible for the excitation of vibrations, and all the gases were found to have a single relaxation time indicating a strong intermodal coupling. The probability, in a collision, of exciting or de-exciting molecular vibrations was found to depend upon the relative energy of approach of the molecules. Molecules with the same number of halogen substitutions resemble each other in this respect. The data suggest that the colliding molecules might form a complex molecule with a short lifetime during which energy exchange takes place readily.
Liquid Surface Tension Measurements by Analysis of Solid-State Curvatures; The Surface Tension of Liquid Germanium
Authors: Sangster R. C. , Carman J. N.
Published: April 2005

A procedure based upon zone-melting techniques has been developed for determining liquid-gas surface tension coefficients for liquids at their melting points by analysis of the surface curvatures of solid specimens. The method can give standard deviations of the mean of the order of ±1 percent. It has been calibrated with lead and cadmium to be valid to within at least ±5—10 percent. The most important factors limiting its range of applicability are crystallographic forces which produce facets on the solid and the difficulty of producing and maintaining a clean liquid-gas surface. The surface tension of liquid germanium at its melting point, 934.5°C, in contact with helium or nitrogen has been found to be 632±5 dyne/cm, in good agreement with a previously reported value.
Absorption Cross Sections of Methane and Ammonia in the Vacuum Ultraviolet
Authors: Sun H. , Weissler G. L.
Published: April 2005

Absorption cross sections of methane and ammonia for electromagnetic radiation in the range from 1300 A to 374 were obtained with a two-meter radius of curvature, grazing incidence vacuum spectrograph. For methane 85 wavelengths were measured. Starting from σ = 14 Mb (1 Mb = 10—18 cm2) at 1300 A, the absorption first increased slowly and then rose more rapidly to a maximum of σ = 56 Mb at 960±278 A corresponding to the first ionization potential of methane. The absorption then decreased gradually to 14 Mv at 374 A. The total f-value pertaining to the transitions of 2p-electrons was found to be 6.1. For ammonia, 100 wavelengths were measured. Band absorption appeared at longer wavelengths. The continuous absorption began near 1210 A and extended to the shorter wavelengths. The structure of the absorption contour suggested the existence of two ionization continua: a weaker one with maximum σ = 21 Mb at 1130±20 A and a larger one with its maximum of 34 Mb at 730±20 A. These two maxima corresponded to the ionization limits of the outer electrons of ammonia. The total f-value was found to be 5.9.
Quantum-Mechanical Properties of a One-Dimensional System Composed of Hard Spheres
Authors: Rubin Robert J.
Published: April 2005

The stationary state wave function for a one-dimensional system of hard sphere particles in a box is known to be a determinantal combination of single particle wave functions. The time-dependent wave function corresponding to a certain class of initially prepared states is shown to be a determinantal combination of single particle time-dependent wave functions. The motion of the center of gravity of such a system of particles is especially simple.
Relative Efficiencies of Quenching of Mercury Resonance Radiation and Their Temperature Independence. Mechanism of Mercury Photosensitized Decomposition of Saturated Hydrocarbons
Authors: Cvetanović R. J.
Published: April 2005

Relative over-all efficiencies of quenching of mercury resonance radiation have been determined for N2O, n-C4H10, C2H6, and C2H4 by studying the binary mixtures of each of the hydrocarbons with nitrous oxide at 23° and 120°C. For N2O and n-C4H10 the relative efficiency of quenching to the ground state as well as the fractions of quenching to the ground and to the metastable 6(3P0) state of mercury for each of the two compounds have also been determined. Temperature independence of the primary quenching processes has been demonstrated.

A proposed mechanism of quenching by saturated hydrocarbons, based on additional experimental information obtained with n-butane alone and its mixtures with nitrous oxide, interprets fully the experimental facts and in particular accounts for the repeatedly observed low quantum yields of hydrogen formation.
Microwave Spectrum of Propiolic Aldehyde
Authors: Howe John A. , Goldstein J. H.
Published: April 2005

The microwave spectrum of propiolic aldehyde has been studied in the 18—37 Kmc region. Analysis of the ground state spectrum provides the following rotational constants: b=4826.31±0.03 Mc, c=4499.75 ±0.03 Mc, and δ=0.00594±0.0030 Mc, consistent with a planar model. Strong vibrational satellites were observed and fitted, and approximate values of the two lowest vibrational frequencies were found from intensity ratios to be roughly 150 cm—1 and 230 cm—1. The dipole moment of the ground vibrational state is 2.46±0.04D, as determined from quantitative Stark effect studies.