bluuebunny/crossref_metadata_2025 huggingface dataset:
General Relation between Potential Energy and Internuclear Distance for Diatomic and Polyatomic Molecules. I
Authors: Lippincott Ellis R. , Schroeder Rudolph
Published: April 2005

A general relation between potential energy and internuclear distance is proposed which is applicable to the ground states of diatomic and polyatomic molecules. The relation has the form V = De[1—exp(—nΔr2/2r)]×[1+af(r)], where the parameter n is defined by the equation n = kere/De. For large values of r, the f(r) term assumes the form of a Lennard-Jones (6—12) repulsive potential. With a = 0 the function assumes a simple form which is numerically easier to use and much more accurate than the Morse function. By using the simple function dissociation energies are readily calculated with greater accuracy than hitherto possible through the use of bond lengths, force constants, and anharmonicity constants. Independent empirical methods are given for evaluating the parameter n and with its use anharmonicity constants as well as dissociation energies may be calculated more accurately than was possible previously. The use of the general relation gives improved correlations and predictions of the five spectroscopic constants re, ke, De, ωeχe, and αe. The wide application of these potential functions to a large number of molecules indicates that the potential energy curves for most molecules have a general form to which the proposed relation is a reasonable approximation. The application of the proposed functions to strongly ionic or charged molecules has not been fully investigated.
Low Resolution Electronic Spectrum of Hexamethylbenzene with Application to Benzene
Authors: Nelson Richard C. , Simpson William T.
Published: April 2005

The crystal spectrum of hexamethylbenzene has been obtained using polarized light in the region 1725—2800 A and the results including extinctions for out-of-plane absorption are interpreted. The vapor spectrum has been determined in the region 1300—2800 A and the solution spectrum down to 2150 A. The vapor spectrum shows a new band at 2350 A. A suggestion is made for determining quantum numbers in the Rydberg series formula.
Analysis of Spin-Spin Multiplets in Nuclear Magnetic Resonance Spectra
Authors: McConnell H. M. , McLean A. D. , Reilly C. A.
Published: April 2005

A systematic procedure is developed for the analysis of the spin-spin multiplets that are observed in the high-resolution NMR (nuclear magnetic resonance) spectra of liquids. It is shown how the symmetry properties of nuclear spin functions can be used to simplify the interpretation of NMR multiplets in terms of the empirical quantities, chemical shifts, and spin-spin coupling constants. It is also pointed out that when NMR multiplets have been properly interpreted in terms of these empirical quantities, it is then possible to predict theoretically relative intensities of multiplets to the same degree of precision as that involved in the measurement of multiplet frequency separations.

As an example the multiplet splittings of the H1 and F19 resonances in 1,1-difluoroethylene are analyzed using the procedure proposed in the present paper.
Self-Diffusion in α White Phosphorus
Authors: Nachtrieb Norman H. , Handler George S.
Published: April 2005

The coefficient of self-diffusion in α white phosphorus from 0° to the melting point is given by the equation D=1.07×10−3exp[−9400/RT]+2×1046exp[−80 600/RT]cm2sec−1.Only the first term is important for temperatures below 30°, where the vacancy mechanism is believed to operate. The activation energy in this range is in excellent agreement with the value predicted from the latent heat of fusion. A second mechanism begins to become important above 30°, with an activation energy of 80 600 calories and an exceedingly large entropy. This process is interpreted as a comparatively large scale disorder which arises on multiple vacancies. The entropy and energy are consistent with the view that liquid microphase regions containing, on the average, about 130 molecules and 10 distributed vacancies are the principal centers of diffusion near the melting point.
Effect of Pressure on Self-Diffusion in White Phosphorus
Authors: Nachtrieb Norman H. , Lawson A. W.
Published: April 2005

Pressure decreases the rate of self-diffusion in α white phosphorus. At 30°C the activation volume is 30 cm3, a value which indicates that considerable lattice relaxation takes place about vacancies. At 41.30°C the activation volume is about an order of magnitude larger, a behavior consistent with a view that lattice disordering on a comparatively large scale begins well below the melting point.
Methyl Alcohol. I. Microwave Spectrum
Authors: Venkateswarlu Putcha , Edwards Howard D. , Gordy Walter
Published: April 2005

The J=0→1, K=0→0 rotational lines of methyl alcohol have been observed and identified with the Stark effect for C12H3O16H, C13H3O16H, C12H3O16D, C13H3O16D, C12D3O16H, and C12D3O16D. These lines are obtained not only for the molecules in the ground state but also for those in the first two torsional excited states, n=1 and n=2. All these lines except those of the C12D3O16D were observed to be doublets, the doublet separation being different for different molecules. Some further experimental data on C12D3O16H, C12H3O16D, and C13H3O16H are included in this paper.
Methyl Alcohol. II. Molecular Structure
Authors: Venkateswarlu Putcha , Gordy Walter
Published: April 2005

From the moments of inertia of six different isotopic species of methyl alcohol as obtained from the J=0→1 rotational lines a complete structural determination of methyl alcohol has been made. The structural parameters so obtained are the following : dOH=0.956±0.015 A, dCO=1.427±0.007 A, dCH=1.096 ±0.010 A, ∠HCH=109°2′±45′, ∠COH=108°52′±2°, and the distance of the oxygen atom from the symmetry axis of the CH3 group=0.083±0.005 A.
Determination of the Atomic Weight of Silicon by Physical Measurements on Quartz
Authors: Frondel Clifford , Hurlbut C. S.
Published: April 2005

The value 28.095±0.005 for the atomic weight of silicon has been obtained through precision measurements of the density and unit-cell volume of an unusually pure crystal of natural quartz, SiO2. The value is based on the Avogadro number, 6.02338, and wavelength conversion factor, 1.002030, of Birge (1945). The following experimental data were obtained: density in g/cc in vacuum at 25°, 2.64847±0.0001; unit-cell dimensions in kX at 25° and corrected for refraction, a0 4.90360, c0 5.39417, both ±0.0001; indices of refraction for λ589.29 mμ at 18°, nO 1.544258, nE 1.553380, both ±0.00001; inversion temperature 573.3° on both heating and cooling cycles. Direct analysis gave (weight percent): Li2O 0.0005, Na2O 0.0004, K2O 0.0002, Al2O3 0.0008, TiO2 0.0001, MnO2 0.00002, Fe2O3 0.0000. The major systematic errors in this method stem from compositional variation in the quartz, of the nature of a coupled substitution of Al for Si with interstitial (Li,Na), and probably lead to a high value for the atomic weight. For purposes of comparison, data are also given for smoky quartz, rose quartz, and a synthetic quartz containing much Al and Li in solid solution.
Effects of Anharmonicity of Vibration on the Diffraction of Electrons by Free Molecules
Authors: Bartell L. S.
Published: April 2005

The increased experimental precision now attainable in electron diffraction by free molecules has necessitated a re-examination of the methods of interpretation of diffraction data to allow for the effects of non-rigidity of molecules. It is shown that conventional procedures of analysis of data lead to ambiguous results which are likely to differ from the true equilibrium internuclear distances by the order of 0.01 A. More exact expressions are presented for the intensity of electrons diffracted by vibrating molecules and for the corresponding experimental radial distribution curves in terms of the parameters characterizing the potential fields of the molecules. The case of diatomic molecules is treated in detail, including the effect of temperature, assuming a Morse potential energy function. Some aspects of polyatomic molecules are discussed.
Entropy, Heat Capacity, and Heats of Transition of 1,2,3-Trimethylbenzene
Authors: Taylor R. Dean , Johnson B. H. , Kilpatrick John E.
Published: April 2005

The heat capacity and the heats and temperatures of transition of 1,2,3-trimethyl benzene have been determined experimentally. The entropy of the ideal gas at 25°C and one atmos has been found to be 91.98±0.15 cal/deg mole.
Infrared and Raman Spectra of Nitrogen Trifluoride
Authors: Pace E. L. , Pierce Louis
Published: April 2005

The infrared spectrum of gaseous nitrogen trifluoride has been investigated with prism instruments in the range from 400 cm—1 to 3000 cm—1. The Raman spectrum of liquid nitrogen trifluoride has been investigated in the range from 400 cm—1 to 2000 cm—1. The fundamental frequency assignment made from the infrared data is ν1(A1) = 1031 cm—1, ν2(A1) = 642 cm—1, ν3(E) = 907 cm—1, and ν4(E) = 497 cm—1. The corresponding Raman shifts in the liquid are ν1(A1) = 1050 cm—1, ν2(A1) = 667 cm—1, ν3(E) = 905 cm—1, and ν4(E) = 515 cm—1.

Differences from the results of previous investigators appear either in the assignment of the fundamental frequencies or in the interpretation of the overtone and combination bands in the infrared spectrum. The present results are considered more reliable because of (1) the added weight of an investigation of the Raman spectrum and (2) the use of a sample of known high purity.
Infrared Spectra of Liquid Anhydrous Hydrogen Fluoride, Liquid Sulfur Dioxide, and Hydrogen Fluoride-Sulfur Dioxide Solutions
Authors: Maybury Robert H. , Gordon Sheffield , Katz Joseph J.
Published: April 2005

The infrared spectra of anhydrous liquid hydrogen fluoride, anhydrous liquid sulfur dioxide and mixtures of the two have been measured in the region from 1μ to 25μ. A value for the extinction coefficient for the polymer peak in the region higher than previously reported has been found, reflecting the existence of a greater proportion of higher hydrogen fluoride polymers in the liquid as compared with the gas. A study of the change in the spectra of solutions of varying concentration of anhydrous liquid hydrogen fluoride in anhydrous liquid sulfur dioxide has been made and its possible relation to the structure of the polymers in liquid hydrogen fluoride examined. The possible applicability of obtaining spectra of protein dissolved in anhydrous liquid mixtures of hydrogen fluoride and sulfur dioxide has been explored and a spectrum of silk fibroin in this solvent is presented.
Coupling of the Out-of-Plane Bending Mode in Nitrates and Carbonates of the Aragonite Structure
Authors: Decius J. C.
Published: April 2005

The infrared absorption of polycrystalline samples of KNO3 and BaCO3 in the form of Nujol mulls has been observed between 11.3 and 12.5 microns under conditions such that the rotational lines of the NH3 spectrum separated by 1.5 cm—1 could be clearly resolved. When the N15 or C13 content is increased to the order of 50 percent, fine structure is observed which is not present e.g., in NaNO3, which possesses a crystal structure similar to calcite. The fine structure is interpreted by postulating a force constant which couples the out-of-plane vibrations of nearest neighbors in the aragonite-type lattice.

Very satisfactory agreement between the calculated and observed spectra is then found; in the case of BaCO3, the vibrations of CO3 ions which occur in isotopic isolation, as pairs, triplets, and quadruplets are resolved. The significance of the coupling constant is discussed; in principle, it may be used to evaluate the dipole derivative for the mode under consideration.
Evaporation of Submicroscopic Ice Crystals
Authors: Gourley Mary Foulks , Crozier W. D.
Published: April 2005

Experiments, designed to interpret certain meteorological observations, provide evidence that very small ice crystals may have evaporation rates much lower than predicted on the basis of the vapor pressure of macroscopic ice. Small ice crystals, formed by spontaneous sublimation in nuclei-free air, were suspended in a strongly desiccating atmosphere for a time far longer than should have been sufficient for their complete evaporation. Though they decreased in size below the minimum observable optically, their presence was demonstrated by their ability to nucleate visible ice particles when exposed to a supersaturated atmosphere. In representative experiments, ice-forming nuclei were observed in a 250-cm3 chamber three hours after the admission of nucleus-free ice particles of about 1-micron radius, the chamber containing an atmosphere at —20°C with water vapor pressure at about 50 percent of saturation with respect to macroscopic ice. There was some evidence, however, that the ice-forming residues diminish in effectiveness at a low time rate.
Photolysis of Hexafluoroazomethane
Authors: Dacey J. R. , Young D. M.
Published: April 2005

Hexafluoroazomethane is decomposed by light of 2537 A to yield nitrogen, hexafluoroethane, perfluorotetramethyl hydrazine, and perfluorohexamethyl tetrazine. The relative amounts of the various products vary with the pressure: the compounds of higher molecular weight being produced more abundantly at higher pressures. A free radical mechanism is proposed for the reaction.
Phase Diagram of Liquid Ozone-Oxygen System
Authors: Brown Callaway , Berger Abraham W. , Hersh Charles K.
Published: April 2005

Vapor pressure composition data for liquid ozone-oxygen mixtures were obtained at —195.5°, —183°, and —180°C. The vapor pressure isotherms were used to construct the boiling point-composition line at one-atmos pressure. The vapor pressure of pure liquid ozone defines an upper limit for the partial pressure of ozone in the vapor in equilibrium with boiling liquid.

The vapor pressure of ozone-oxygen solutions deviates markedly from Raoult's law in a positive direction. It is suggested that the apparent boiling point maximum reported by Schumacher, which implies negative deviations, may be due to difficulties in analysis of ozone at high concentrations where it is subject to decomposition at ordinary temperatures.

Liquid-liquid equilibrium data are reported which indicate —180°C as an upper bound for the consolute temperature. The region of two liquid phases extends from 9 to 91 percent ozone by weight at —195.5°C, 29.8 to 72.4 percent at —183°.
Anomalous Light Emission of Azulene
Authors: Beer Michael , Longuet-Higgins H. C.
Published: April 2005

Azulene was found to fluoresce with a frequency corresponding to transition from the second excited singlet level to the ground state. No phosphorescence was observed. No emission corresponding to transition from the lowest excited singlet to the ground state was observed. These phenomena are discussed.
Solution of the Wave Equation for Internal Rotation of Two Completely Asymmetric Molecules
Authors: Burkhard Donald G. , Irvin John C.
Published: April 2005

The wave equation is derived from two completely asymmetric molecules undergoing mutual rotation about a common axis and subject to an arbitrary hindering potential. Matrix elements of the Hamiltonian are evaluated using the wave functions which describe the mutual rotation of two symmetric groups.
Inertial Effects and Dielectric Relaxation
Authors: Gross E. P.
Published: April 2005

The study of dielectric relaxation in compressed gases requires an extension of existing theory. As the gas pressure is lowered below several hundred atmospheres, the inertial response of the dipoles gives rise to large deviations from the Debye equations. The absorption and dispersion depend on collision time and frequency of applied field in a manner which is sensitive to the molecular constants and to the state of dynamical order of the compressed gas.

These phenomena are investigated by studying the response to an alternating electric field of a dilute solution of dipolar molecules in a nonpolar compressed gas. The dipoles are described by a classical distribution function which is a function of angular velocity, orientation, and time. We assume that the duration of collision may be neglected compared to the time between collisions, the period of the applied field, and the mean thermal period. The distribution function satisfies a kinetic equation; the effects of collisions are described by a collision kernel. One kernel yields a soft impact theory which is a generalization of Debye's Brownian motion treatment to include inertial effects. The complex polarization is given in the form of a convergent infinite continued fraction. Other models studied involve strong collisions and partial specular reflection.

A common feature of all models is that the Debye relaxation shape is found at high pressures. Inertial corrections are important in the region between one and a few hundred atmospheres; the corrections depend on the model. Another common feature is the way in which the discrete rotational lines are linked with the Debye spectrum. The collision frequency 1/τ increases with increasing gas pressure; at low pressures it is proportional to the width of a rotation line. At high pressures when the Debye shape is found, the relaxation time t* is given by t* = 1/τ(I/kT). Here I is the moment of inertia of the dipole, k is Boltzmann's constant, and T is the temperature of the reservoir. Thus the relaxation time varies inversely with time between collisions. The physical reason is that collisions hinder the drift motion of the dipoles which is the cause of the relaxation of the polarization.

At lower pressures the main contribution to the polarization arises from dipoles rotating with an angular frequency close to that of the applied field. This is related to the known result that the main contribution to the static polarization is from librating dipoles.
Absorption Spectra of Iodine and Bromine in the Gas Phase and ``Inert'' Solvents. II. Bromine
Authors: Evans Dennis F.
Published: April 2005

The effect of foreign gases on the continuous absorption of bromine in the region 2200 A—5100 A has been studied. Contrary to the results of Bayliss and Rees, no increases in intensity were observed. The absorption of bromine in various inert solvents has also been measured. The results are similar to those obtained with iodine and have been interpreted in an analogous manner. No maxima were found at 2725 A and 2500 A for bromine dissolved in chloroform and cyclohexane, respectively, in disagreement with Aikin, Bayliss, and Rees.
Perfluoroheptane as a Spectroscopic Solvent
Authors: Evans Dennis F.
Published: April 2005

Solvent shifts of ultraviolet absorption bands (relative to the gas phase) have been shown to be much less for perfluoroheptane than for n-heptane. The oscillator strength of the 2400 A band of styrene has been measured in the gas phase and in perfluoroheptane and n-heptane solution. Small increases were observed in solution, which are, however, less than those calculated theoretically.
Infrared Spectrum of Solid Ammonium Azide : A Vibrational Assignment
Authors: Dows David A. , Whittle Eric , Pimentel George C.
Published: April 2005

Infrared spectra of solid ammonium azide at 68°K are presented. The solid, prepared by sublimation onto a cold salt window, seems to be a disordered crystal which becomes ordered on warming above 150°K. The annealed crystal displays spectral features with spacings of 10—20 cm—1 which can be attributed to crystal site perturbations. A band at 1830 cm—1 appears which is assigned as a combination involving a lattice torsional motion of the ammonium ion (420±20 cm—1). A vibrational assignment of solid ammonium azide is made. The vapor over ammonium azide at room temperature contains predominantly hydrazoic acid and ammonia.
Thermodynamics of Sorption by Solids under Finite Strain with Particular Reference to Fibers
Authors: White Howard J.
Published: April 2005

Equations have been derived expressing the conditions of equilibrium for a strained solid absorbent in contact with fluid absorbates. The results are more general than any previously derived and are not limited to infinitesimal strains or isotropic absorbents; it is necessary that the principal axes of stress and of strain coincide. The results are applied to a few cases involving various states of strain in fibrous absorbents such as might be encountered in the textile industry.

One result was obtained which was uniquely different from the usual thermodynamic relations involving hydrostatic pressure. Essentially, three different forms of Gibbs free energy appear. These differ in accordance with the way in which the extensive variable for the absorbent was defined.
Solid Mixture Permittivities
Authors: Brown William Fuller
Published: April 2005

A macroscopically homogeneous aggregate contains two materials A, B, with dielectric constants εA, εB, in volume ratio p: (1—p); what is the dielectric constant of the aggregate? By a method used by Yvon and others in molecular theory, this very old problem is formulated rigorously and solved in series form. One form of the solution is ε/ε′ = 1+⅓p(1—p)(δ′/ε′)2+..., where ε′ = pεA+(1—p)εB, δ′ = εA — εB. The cubic and higher terms depend on statistical properties of particle geometry: namely, on such functions as p(3)123, the probability that three specified points 1, 2, 3 are all in material A. The relation to earlier calculations is discussed.
Non-Newtonian Viscosity of Solutions of Ellipsoidal Particles
Authors: Scheraga Harold A.
Published: April 2005

The specific viscosity, and its dependence on velocity gradient, plays an important role in studies of the structure of macromolecules in dilute solution. A satisfactory theoretical interpretation of the non-Newtonian viscosity of solutions of ellipsoidal particles has been given by Kuhn and Kuhn, and also by Saito, who made use of Peterlin's distribution function for the orientation of particle axes in the streaming liquid and calculated the energy dissipation due to both the hydrodynamic orientation and the Brownian motion. Also, a theory for the non-Newtonian viscosity of solutions of rod-like particles has been developed by Kirkwood. These theories involve extensive computations which have been carried out here with the aid of a computing machine by expressing Saito's results in terms of Legendre coefficients previously evaluated in the related problem of double refraction of flow. As a result, data are available for the dependence of the viscosity factor v on axial ratio and on the parameter α, where α = G/Θ, G being the velocity gradient in sec—1 and Θ being the rotary diffusion constant in sec—1. With these data it will be possible to determine the rotary diffusion constants of ellipsoidal particles from the non-Newtonian viscosity of their solutions, and also to correct viscosity measurements to zero velocity gradient in order to obtain the intrinsic viscosity. Data are also included for the evaluation of Θ from the dependence of v at α = 0 on the frequency of periodic shear waves.
Mechanism of Potential Inversion of the Joshi Effect
Authors: Mohanty S. R.
Published: April 2005

The positive Joshi effect +Δi (i.e., the photoincrease of the current i) increases initially with the exciting ac potential V(<Vm the ``threshold potential'') to a maximum at Vm, decreases precipitously and changes sign (to the negative effect—Δi, i.e., photosuppression of i) at an inversion potential ViI. Beyond ViI, —Δi first increases rapidly and diminishes slowly thereafter. A second inversion, —Δi→+Δi, obtains, in certain systems, at ViII in the region of high V. Oscillographic studies reveal simultaneous occurrence, at V>Vm, of intrinsic (+Δi) and intrinsic (—Δi); the integrating current indicator shows the balance.

The initial +Δi at V<Vm, and its enhancement with V, results from photoelectron emission from the (momentary) cathode of field diminished work function. At Vm, consequent to the continuous discharge and an electron residuum from the antecedent half-cycle, largely enhanced emission and space accumulation of negative ions (from attachment of the electrons) lead to incipience of (—Δi) due to inhibition of γ and ηθg processes. Electrons able to cross the barrier cause (+Δi). The observed co-occurrence of (+Δi) and (—Δi) follows. Beyond Vm, increase in emission due to field reduction of surface work function enhances space charge density and therefore (—Δi). Observed diminution in +Δi follows from the above, and the reduction in the number of photoelectrons able to cross the barrier. At ViI, (+Δi)=(—Δi) and therefore, ±Δi=0. Increase of —Δi above ViI also follows from the above considerations. The decrease in attachment probability P=f(p/F), where p is the gas pressure and F the field, leads to subsequent diminution of (—Δi) at large V. Increase in the associated (+Δi) is a contributory factor, and above ViII causes the observed positive effect.
Oxidation States of Phosphorus-32 Produced by Neutron Irradiation of Potassium Chloride
Authors: Carlson T. A. , Koski W. S.
Published: April 2005

An investigation of the oxidation states of P32 formed by neutron irradiation of KCl shows that like the simultaneously formed S35 the ratio of the different oxidation states depends on the preirradiation treatment. Through outgassing of the crystals results in the production of lower oxidation states. On the other hand, the oxidation states of P32, unlike S35, are strongly affected by the presence of x- or γ radiation. The recoil energy of the newly formed P32 fragment seems to have little effect on its final oxidation state.
Calculation of the Correction to be Applied to Gas Isotherms Measured in the Presence of Mercury
Authors: Jepson W. B. , Rowlinson J. S.
Published: April 2005

A calculation is made of the correction for the volatility of mercury which should be applied to observed pressures of compressed gases, when mercury is used as the confining fluid. The usual correction is simply the subtraction of the normal vapor pressure of mercury corrected for the effect of hydrostatic pressure (the Poynting effect). Here we show that this is an inadequate treatment of the problem, as the mixture of mercury atoms and compressed gas cannot behave as an ideal mixture. An estimation of the intermolecular forces between mercury atoms and the added gas leads to values of the virial coefficients from which a revised correction can be computed, assuming that the system is at equilibrium. This revised correction can be considerably larger than the usual correction and is often of opposite sign.
Adsorption of Helium on Titanium Dioxide
Authors: Aston J. G. , Mastrangelo S. V. R. , Tykodi R. J.
Published: April 2005

The absorption characteristics of helium adsorbed on TiO2 (anatase) have been studied in the temperature range 2°—20°K. Isotherms are reported at 2.60°, 4.17°, 13.96°, and 20.28°K. Isosteric heats of adsorption at low coverage have been measured at 17.1°K. The data are interpreted in terms of a previously discussed model.
Vibrational Spectra and Structure of Cyclopropane and Cyclopropane-d6
Authors: Baker A. W. , Lord R. C.
Published: April 2005

Cyclopropane-d6 has been synthesized from deuterium oxide and magnesium tricarbide in steps giving successively methyl acetylene-d4, propylene-d6, allyl chloride-d5, 3-bromo-1-chloropropane-d6, and cyclopropane-d6. Infrared spectra of cyclopropane and cyclopropane-d6 have been obtained in the spectral region 350 to 3700 cm—1 for the vapor and 650 to 3700 cm—1 for the liquid. Raman spectra, including semi-quantitative depolarization factors, have been determined for the liquid state. The spectroscopic results satisfy the Teller-Redlich product rule for a molecule of D3h symmetry. All active fundamentals in cyclopropane-d6 but one have been directly observed. The inactive fundamentals in both molecules have been located provisionally from overtone assignments. An attempt to determine the molecular geometry from rotational contours of the infrared bands was not successful, but high-resolution work on cyclopropane-d6 shows that the C–C distance is 1.524±0.014 A.
Intermolecular Potentials of Argon, Krypton, and Xenon
Authors: Whalley E. , Schneider W. G.
Published: April 2005

The intermolecular potentials of argon, krypton, and xenon are investigated using the recently measured second virial coefficients and the crystal properties at 0°K. The potential functions considered are the 9:6, 12:6, and exp:6. The methods of determination of parameters are reviewed and the method of least squares used in this paper described. All the potentials fitted the second virial coefficient very well, but with the same parameters fitted the crystal properties only moderately well.
Excluded Volume in Polymer Chains
Authors: Fixman Marshall
Published: April 2005

A perturbation theory of the excluded volume effect in chain polymers is developed. The theory is applied to the mean square end-to-end distance, 〈L2〉, of a linear chain (second-order perturbation), and to the mean square radius of a linear and a branched chain (first-order perturbation). Flory's approximate theory is found to be in fair agreement with the second-order perturbation theory. Integro-differential equations are developed to discuss the behavior of 〈L2〉/nb2 as n→ ∞, for a chain composed of n segments of length b.
Study of Chemical Reaction Mechanisms with Molecular Beams. The Reaction of K with HBr
Authors: Taylor Ellison H. , Datz Sheldon
Published: April 2005

The reaction between K and HBr has been studied by a molecular beam technique, using as a detector a surface ionization gauge with a tungsten and a platinum alloy filament, the former sensitive to KBr as well as to K and the latter essentially to K only. The activation energy is 3.4±0.1 kcal/mole and the probability or steric factor is about 0.1. The angular distribution of the KBr suggests that collisions with the H end of the HBr are more often fruitful than other configurations. The total collision cross section for a beam of K at 504°K in HBr at 401°K is 850×10—16 cm2.
Vibration-Rotation Band ν2 of Heavy Water Vapor
Authors: Dickey Fred P. , Hoffman James M.
Published: April 2005

The vibration-rotation band ν2 in the heavy water vapor (D2O) spectrum has been remeasured. An analysis of the rotational structure has been carried out. From the interpretation of the data the band center, as well as the value of the reciprocals of inertia have been determined. The band center is found to be 1178.45 cm—1 and the reciprocals of inertia are A (V) = 16.650 cm—1, B (V) = 7.345 cm—1, and C (V) = 4.795 cm—1.
Magnetic Annealing in Perminvar. II. Magnetic Properties
Authors: Nesbitt E. A. , Heidenreich R. D.
Published: April 2005

Previous work on Alnico single crystals (permanent magnet alloy) showed that magnetic torque reversals are associated with an inhomogeneous structure. More recently, it has been found that alloys of iron, nickel, and cobalt in the Perminvar region also exhibit these torque reversals although the alloys are considered to be solid solutions. An inhomogeneous structure occurs simultaneously with the torque reversals in some of these alloys. The inhomogeneous structure has been observed by means of electron diffraction, and the observations have been interpreted to mean that there are faults in the lattice normal to [111] directions. The faults form in the temperature region where the magnetic field heat treatment is effective and their density is roughly proportional to the response of the magnetic field treatment. When the crystals are not heat treated in a field, the faults are arranged to have cubic symmetry and their magnetic anisotropy has cubic symmetry. When the crystals are heat treated in a magnetic field, electron diffraction indicates that the faults are usually affected also.

Evidence has been obtained that small amounts of oxygen as an impurity in Perminvar cause both the faulting and the heat treatment in a magnetic field. An extremely small amount of oxygen (0.0014%) is sufficient to cause such effects.

In a more detailed sense we feel that the magnetic anisotropy introduced by heat treatment in a magnetic field probably arises either from short range order within the faults or from the arrangements of the faults each of which is parallel to a (111) into regions whose shape anisotropy is along the direction of the magnetic field.
Ferroelectric Properties of Colemanite
Authors: Wieder H. H.
Published: April 2005

The ferroelectric properties of the calcium borate mineral colemanite are investigated in the ferroelectric and paraelectric temperature regions. It is shown that Devonshire's phenomenological theory may be applied successfully to account for the experimental measurements of spontaneous polarization and electrical susceptibility over a wide temperature range. The thermodynamic transition is confirmed to be of second order occurring for unbiased crystals at −7°C. It is shown, in general, that the temperature τ0 at which such a transition takes place depends upon the effective electric field E as τ0 = kE⅔ where k is a constant evaluated from Devonshire's expansion. The effect of space charge fields are evaluated and a comparison is presented between the ferroelectric properties of colemanite and those of KDP.
InAs1-xPx as a Thermoelectric Material
Authors: Bowers R. , Bauerle J. E. , Cornish A. J.
Published: April 2005

Measurements of the electrical conductivity σ, the thermal conductivity K, and the Seebeck coefficient (thermoelectric power) α, of InAs1−xPx have been made at high temperatures with x varying from 0 to 0.4. Between 450° and 800°C, the average thermoelectric figure of merit (z = α2σ/K) increases moderately with x for small values of x, reaching a maximum near x = 0.1, and subsequently decreasing. Between 450 and 800°C, the average z for x = 0.1 is equal to 0.63 × 10−3(°K)−1, a 15% improvement over InAs. For the same figure of merit, the Seebeck coefficient and electric resistivity is higher in the ternary than in the binary InAs; this is advantageous for the design of thermoelectric devices. Previous values for the thermoelectric figure of merit of InAs are revised.
Contribution to a General Theory of Thermocouples
Authors: Boerdijk A. H.
Published: April 2005

Application of thermodynamics of irreversible processes to a thermocouple of which (a) the bars have an arbitrary shape, (b) the properties of the materials are arbitrary functions of temperature, and (c) the composition is, under certain restrictions, inhomogeneous and anisotropic, leads through introduction of a single place coordinate to two nonlinear differential equations describing the stationary distribution of temperature and electrical potential. Output powers and efficiencies are expressed in terms of the temperature gradients in the bars. The maximal values of the efficiencies obtained by variation of the shape of the bars are independent of the shape. Upper bounds of the efficiencies attainable by stationary thermoelectric conversion are derived. If the shape of the bars is restricted to general cylinders and truncated wedges or cones the transient behavior is described by two partial differential equations which contain two independent variables only. A periodic ripple in the electrical current has the same effect as a decrease of the electrical conductivities of the materials.
Dynamic Properties of the Polarizability in BaTiO3 Crystal
Authors: Husimi Kazuo
Published: April 2005

The second harmonic distortion by a BaTiO3 crystal of a small high-frequency sinusoidal electric field, superimposed on a low-frequency switching field, is studied by the filter method. From the phase relationship of the second harmonic distortion with respect to the measuring signal, together with the increase of the fundamental component of the capacitive current, it is concluded that the polarizability increases markedly for the backward direction during switching.
Ion Drag Pressure Generation
Authors: Stuetzer Otmar M.
Published: April 2005

A theory of pressure buildup under unipolar ion conduction is presented and verified experimentally. Constriction of the current flow leads to sizeable pressures in insulating liquids.
Study of Band Structure of Intermetallic Compounds by Pressure Experiments
Authors: Sagar A. , Miller R. C.
Published: April 2005

The effect of hydrostatic pressure on the transport properties of n-type GaSb, InP, GaP, and p-type PbTe was measured to study their band structure. (1) The Seebeck coefficient, Hall coefficient, and resistance of three n-GaSb samples were measured as a function of hydrostatic pressure up to 17 000 atm between 200° and 400°K. The Seebeck coefficient α increased with pressure and approached a constant value at about 10 000 atm. The saturation value of α does not follow the simple 32 lnT relation for any of the samples; e.g., for a sample with RH(77°K) ≈95 coul−1 cm3, the saturation value of α decreases with temperature. The contribution due to the phonon-drag effect has been considered as a possible explanation for this phenomenon. (2) The conductivity of p-PbTe increased almost exponentially with pressure both at 300° and 194°K; the Hall coefficient at 300°K decreased by about 5% at 8000 atm, while the conductivity increased by 55% at this pressure. (3) The resistance of n-InP samples increased with pressure; the pressure coefficient was found to be bigger for samples with higher impurity contents. (4) The resistance of an n-GaP sample decreased by about 3% at 10 000 atm.
Band Structure of the Intermetallic Semiconductors from Pressure Experiments
Authors: Paul William
Published: April 2005

Three types of conduction band extrema in the (000), (100), and (111) directions in k space seem to determine many of the properties of the group 4 and group 3–5 semiconductors. Early experimental work on the pressure coefficients of the energy separations of these extrema from the valence band maximum energy, carried out on Ge (111), (000), (100), Si (100), and InSb (000), suggested that the three pressure coefficients might be independent of the specific element or compound in the group 4 and group 3–5 series. This work is discussed in detail, and the theoretical basis is briefly considered. All of the completed pressure measurements on these compounds are critically reviewed, and the correlation of unique pressure coefficients with specific band edges examined. It is demonstrated that pressure experiments can be planned to show up details of the band structure unavailable for study at atmospheric pressure. Particular attention is paid to GaP, and a new model for excess absorption occurring in n-type samples of this compound and in Si, GaAs, and AlSb is suggested. The application of similar techniques to PbS, PbSe, and PbTe is discussed, and results of electrical and optical measurements of energy gap and electron and hole mobilities presented.
Lattice Absorption in Gallium Arsenide
Authors: Cochran W. , Fray S. J. , Johnson F. A. , Quarrington J. E. , Williams N.
Published: April 2005

A series of detailed measurements of the lattice absorption bands of gallium arsenide has been made over the wavelength range 10–40 μ and over the temperature range 20–292°K. These results can be interpreted in terms of multiple phonon interactions involving five characteristic phonon energies. These results, along with the known elastic constants, have enabled us to supply all the relevant data for a computation of the complete phonon spectrum using an extension of the shell model.
Magnetoreflection Experiments in Intermetallics
Authors: Wright George B. , Lax Benjamin
Published: April 2005

Magnetoreflection experiments involving both intraband and interband transitions can provide valuable information about the electronic band structure of semiconductors. In the intraband experiments, performed near the plasma reflection edge, the application of a magnetic field splits the edge and results in the formation of two minima separated by the cyclotron frequency. It is thus possible to determine the cyclotron frequency directly, at room temperature, and for high carrier concentrations. When scattering losses are taken into account in the theory, it becomes possible to determine the carrier concentration, scattering time, and effective mass from the optical measurements alone. The theory of the effect is discussed for applied magnetic field transverse and parallel to the direction of propagation, and experimental results are presented for InSb, InAs, and HgSe. A consistent fit to Kane's theory for the variation of mass with concentration in InSb is obtained when previously published data have been corrected for reststrahl dispersion.

Interband magnetoreflection experiments can be useful in cases where high absorption coefficients or difficulty of preparing thin samples make transmission experiments unfavorable. This type of experiment yields information on energy band gaps, effective masses, and g factors. Experimental data for the direct transition in InSb are presented.
Oscillatory Magnetoabsorption in InSb Under High Resolution
Authors: Zwerdling S. , Kleiner W. H. , Theriault J. P.
Published: April 2005

Polarized oscillatory magnetoabsorption spectra of exciton formation transitions in InSb have been measured under high resolution at liquid helium temperature. An unstrained high-mobility sample 5 μ thick and magnetic fields up to 39.1 kgauss were used. Diffraction grating dispersion for the region 3.7<λ<6.0 μ made possible a resolution of 1−7×10−4 ev and the determination of absorption maxima to ±5×10−5 ev. Sixteen minima were resolved with E⊥B for a field of only 5.0 kgauss. The initial interpretation of the detailed spectra obtained involved fitting theoretical spectra calculated from the theories of Kane, Luttinger, and Elliott-Loudon in order to account for band nonparabolicities, valence band degeneracy effects, and exciton binding energies, respectively. The results experimentally established the light-hole nonparabolicity, the valence band degeneracy effects for low magnetic quantum numbers, and the existence of high-field excitons in InSb.
Optical Absorption Edge in GaAs and Its Dependence on Electric Field
Authors: Moss T. S.
Published: April 2005

Values of absorption constant covering the range 1 cm−1 to 104 cm−1 have been derived from transmission measurements made on single-crystal gallium arsenide. The absorption edge is very steep up to ∼4000 cm−1, where there is a knee beyond which the absorption increases relatively slowly with photon energy. The energy bands have been calculated using Kane's theory. From these a theoretical absorption curve has been obtained which shows very good agreement with the experimental data.

Using semi-insulating material, it has been possible to measure the shift of the edge with applied electric field. The effect is small (∼200-μ ev shift for 5000-v/cm field) but is in good agreement with theory.
Energy of Spectrum and Scattering of Current Carriers in Gallium Arsenide
Authors: Nasledov D. N.
Published: April 2005

Conductivity in impurity bands is observed in gallium arsenide at low temperatures. The impurity banding phenomena observed in n- and p-type crystals are markedly different due to the wide divergence in their effective masses. In the temperature interval where the crystal conductivity is determined by conduction in the impurity band, resistivity of n-type material decreases with increasing magnetic field.

The temperature dependences of carrier mobility indicate that at low temperature the impurity ions play the dominant role of the scattering centers. In order to investigate scattering processes more thoroughly, studies were made of the thermomagnetic Nernst-Ettingshausen effects which are very sensitive to the scattering mechanism. It was found that, in the case of nondegenerate specimens at low temperatures, scattering by impurity ions dominates, and at high temperatures by acoustical lattice vibrations; scattering by acoustical lattice vibrations becomes dominant even at low temperature in specimens of high degeneracy. Scattering was also investigated in indium arsenide and indium antimonide.
Optical Properties of Lead-Salt and III–V Semiconductors
Authors: Stern Frank
Published: April 2005

Dispersion relations for optical properties of solids, and a sum rule for the imaginary part of the dielectric constant, are reviewed and applications to semiconductors are described. Plasma frequencies, for which the real part of the dielectric constant vanishes, are associated with lattice vibrations, with free carriers, and with valance electrons. Gottlieb's infrared optical constants for LiF are in good agreement with the lattice vibration sum rule using unit effective charge. Dispersion relations for reflectivity have been used by Dixon to analyze optical constants of p-type PbTe in the infrared region where free-carrier effects dominate. He finds an effective mass at room temperature which rises from 0.1m to 0.3m as the carrier concentration is increased from 3×1018to 1020 cm−3. Morrison has measured the reflectivity of InAs, InSb, and GaAs and finds curves which agree well with those of Tauc and Abrahám. His analysis of these results using the dispersion relation predicts a plasma energy near 7 ev in these materials. Free carrier absorption in several III–V compounds and in PbS and PbTe is proportional to λp at long wavelengths, where p varies between 2, for InSb and AlSb, and 3, for InAs and GaAs. For n- and p-type PbS Riedl finds p=2.4. He observes additional structure near the intrinsic absorption edge of p-type PbTe, resembling that observed in n-type GaAs and GaP, which may be associated with a valence band about 0.1 ev below the band edge. The absorption coefficient near the absorption edge of all the lead compounds and of InAs is proportional to eℏω/kTeff, with 80°K<Teff <120°K for measurements taken at room temperature. Impurity effects on the energy gap are discussed in terms of a simple model.
de Haas-van Alphen Effect in p-Type PbTe and n-Type PbS
Authors: Stiles P. J. , Burstein E. , Langenberg D. N.
Published: April 2005

A study of the de Haas-van Alphen oscillations in the magnetic susceptibility has been carried out in p-type PbTe and n-type PbS. Measurements have been made on oriented single crystal samples with carrier concentrations of the order of 1018/cm3 in pulsed magnetic fields up to 125 kgauss. The results for p-type PbTe indicate that the valence bands have a maximum at k=0, and four equivalent maxima at the {111} Brillouin zone faces. The 〈111〉 ellipsoids have a longitudinal mass to transverse mass ratio of 6.4±0.3. From the temperature dependence of the amplitude of the oscillations we obtain a value of 0.043±0.006 m0 for the transverse effective mass. The data indicate that the (000) maximum and the (111) maxima lie within 0.002±0.002 ev of each other. The data also indicate an effective broadening temperature of about 8°K which is attributed to inhomogeneities in the carrier concentrations in the samples investigated. Preliminary results on n-type PbS show a single isotropic Fermi surface cross section with a cyclotron mass of 0.14±0.04m0. The direct and indirect optical interband transitions are discussed in the light of these results.