bluuebunny/crossref_metadata_2025 huggingface dataset:
Generalized Perturbation Method Employing Nonorthogonal Functions
Authors: Blinder S. M.
Published: January 2005

A method is developed for solving second-order perturbation problems without explicit knowledge of the higher molecular states. This method involves, in principle, a transformation of basis from the set of orthonormalized eigenfunctions of the unperturbed molecular Hamiltonian to an arbitrary set of functions not, in general, either normalized or mutually orthogonal, but of such symmetry that perturbation matrix elements connecting them to the ground state do not vanish. If the new basis is chosen expediently, convergence to second-order eigenvalues may be attained with a small number of functions. The method is related to the conventional perturbation and variational approaches. As an illustration, the perturbed harmonic oscillator is treated.
Temperature Dependence of Quadrupole Resonance Frequencies under Constant Pressure
Authors: Brown R. J. C.
Published: January 2005

The theory of the temperature dependence of pure quadrupole frequencies under constant volume conditions is modified when constant pressure conditions apply. For the case of molecular crystals the first and second derivatives of frequency with respect to temperature have been calculated assuming that (i) the quadrupole coupling constant is independent of volume, and (ii) the lattice frequencies vary linearly with temperature. These derivatives have been evaluated experimentally for the α phase of p-dichlorobenzene, and comparisons made with the theory; good agreement with previous work on the pressure dependence of quadrupole frequencies is obtained.
Evaluation of One-Center Electron Repulsion Integrals between Certain s-Type Atomic Orbitals
Authors: Jones Walter D. , Brooks F. L.
Published: January 2005

A general formula is derived for one center s-type electron repulsion integrals for the set of basic atomic orbitals which involve the complete set of associated Laguerre functions of order (2l+1) and degree (n+l+1) with a single orbital exponent.
Diffusion of Impurities in Amorphous Polymers
Authors: Lawson A. W.
Published: January 2005

The data of Ryskin on diffusion of impurities into amorphous polymers appear to be consistent with the prediction of elastic continuum theory that the ratio of the entropy of activation, ΔS‡, to the enthalpy of activation, ΔH‡, is independent of the nature of the diffusing impurity. The ratio, ΔS‡/ΔH‡, depends only on the host polymer, and is approximately equal to 4α, where α is the volume thermal expansion coefficient of the polymer. The concentration dependence of the diffusion coefficient is roughly explained by the continuum theory on the basis of swelling.
Matrix Isolation Studies: Infrared Spectra of Intermediate Species in the Photolysis of Hydrazoic Acid. II
Authors: Van Thiel Mathias , Pimentel George C.
Published: January 2005

Further infrared studies of the photolysis of hydrazoic acid in solid nitrogen at 20°K confirm the spectroscopic detection of unusual molecular species, as postulated earlier. Neither hydrogen bonding nor tautomerism of HN3 can account for the new bands detected. The two most prominent of these, at 1325 and 1290 cm−1, are shifted by a factor near √2 when DN3 is photolyzed. The data tend to confirm the presence of imine radical NH2 but two alternate interpretations, diimide N2H2, or azide amine NH2N3, cannot be eliminated at this time.
Microwave Spectrum, Structure, Dipole Moment, and Nuclear Quadrupole Effects in Vinyl Chloride
Authors: Kivelson Daniel , Wilson E. Bright , Lide David R.
Published: January 2005

The microwave spectra of nine isotopic species of vinyl chloride have been measured and analyzed, yielding moments of inertia from which a molecular structure was calculated. The bond lengths found are (in A) C=C 1.332, C–Cl 1.726, average C–H 1.08. The bond angles are C2C1Cl 122°, C2C1H1 124°, C1C2H3 (cis to Cl) 121°, C1C2H2 (trans to Cl) 120°. Planarity was assumed.

The chlorine nuclear quadrupole hyperfine lines were reexamined. From the data for several isotopic species it was shown that the C–Cl bond direction is within five degrees of a principal axis of the field gradient tensor. The lack of cylindrical symmetry of the field gradient about the C–Cl bond was confirmed. This is evidence that the observed shortening of the C–Cl bond is at least in part due to conjugation with the C=C double bond and not solely to hybridization effects.

The component of dipole moment along the a inertial axis was found to be 1.42±0.02 D.
Hydrogen Ion Titration Curve of a Polynucleotide Capable of Undergoing a Helix-Coil Transition
Authors: Steiner R. F.
Published: January 2005

A theory is developed for the hydrogen ion titration curve of doubly stranded helical polynucleotides for which the two strands are nonidentical and very long. It is shown that for pronounced sharpening to occur the binding (or dissociation) of a proton must favor the rupture of the internucleotide hydrogen bonding and also the addition to a sequence of ruptured bonds must be energetically favored over the formation of a new sequence.
Inhomogeneous Field Method for the Study of Large Polarizable Particles
Authors: Prock Alfred , McConkey Gladys
Published: January 2005

An inhomogeneous electric field applied to a solution of polarizable particles causes a movement of the particles toward the region of lowest potential energy. The resulting creation of concentration gradient can be observed, for large particles, by a method involving measurement of capacitance change of a cylinder containing a solution of the polymer.

This effect has been measured in terms of weight average molecular weight; the system investigated is polystyrene in cyclohexane. The basic Debye theory relating capacitance change at equilibrium to weight average molecular weight has been extended to make it applicable to experimental conditions found to be necessary in work with random coil polymers. The theory is substantiated by the agreement obtained between molecular weight calculated by this method and by the method of light scattering.

The polarizability of the particles present determines not only their equilibrium position, but also the rate at which they move. This idea is the basis of a theory presented here relating the time dependence of capacitance change to molecular weight distribution of a given sample. Another theory presented here shows how the shape of the curve for capacitance change as a function of applied field strength is related to the moments of the weight distribution function of the polarizable substance.
Dielectric Properties of Linear Polyamides
Authors: McCall David W. , Anderson Ernest W.
Published: January 2005

The dielectric constant and loss have been measured for several linear polyamides over a range of frequency and temperature. At low frequencies and elevated temperatures, proton conduction through the amorphous regions gives rise to a Maxwell-Wagner loss, while at high frequencies and high temperatures dipole relaxation of the amide groups contained in the amorphous regions gives rise to a typical loss peak. Nylons 6, 6–6, 6–10, 7–9, 6–9, and 10–10 yield very similar results. The N-methylated derivative of nylon 10–10 exhibits a much smaller direct current conductivity than nylon 10–10 (when compared at temperatures of equivalent chain activity) owing to the absence of amide protons.
On Chemical Reactions in Free Molecule Flow
Authors: Chambré Paul L.
Published: January 2005

This paper deals with heterogeneous chemical reactions within systems in which the relevant geometric dimensions are small compared with the mean free path of gas molecules. A typical example can be found in a surface reaction occurring at moderate pressures inside the pore of a catalyst with a radius of several angstroms.

Specific problems of this type have in the past been formulated, subject to the well-known limitations of ordinary diffusion theory, in terms of differential equations for the species concentrations. This in turn supposes that the reaction pattern is dependent on local conditions. A more general and exact formulation given in the following shows that the concentration of a molecular species at a point is determined by the concentration distributions of all species stemming from the entire system. Thus one is led to a formulation in terms of integral equations. In an application of the theory the validity of the conventional differential equation approach is investigated and is found to yield satisfactory results only under certain limiting conditions.
Infrared Absorption Spectrum of the Silicate Ion in the Garnet Structure
Authors: Wickersheim K. A. , Lefever R. A. , Hanking B. M.
Published: January 2005

Infrared absorption bands at 912 and 861 cm−1 exhibited by some crystals of yttrium iron garnet and similar bands exhibited by some rare earth iron garnet crystals have been identified as vibrational fundamentals of a silicate ion impurity. The bands are assigned to split components of a triply degenerate vibration (ν3) of the tetrahedral SiO4 ion. The splitting of this vibration into a nondegenerate and a doubly degenerate vibration is attributed to distortion of the silicate ion along an S4 axis by the garnet structure. Integrated absorption measurements identify the 912 cm−1 band as the nondegenerate component.

Information obtained from the isolated silicate ion in yttrium iron garnet is used to interpret the spectra of the silicate garnets. Complete removal of the degeneracy of vibrations arising from ν3 is observed in the silicate garnets, suggesting that the majority of the silicate ions possess a local symmetry lower than that predicted by the assigned space group Ia3d—Oh10.
Streaming Birefringence and Optical Relaxation Time of Vanadium Pentoxide Sols
Authors: Foreman William T.
Published: January 2005

Maxwell constant and optical relaxation time is studied for V2O5 sols having concentrations which range from 0.01 to 0.1 volume percent using mercury green, 5461 A, and mercury red light, 6000 to 6800 A. These quantities were measured in a device which sheared the sols between two coaxial discs, that is, in a direction which corresponds to the radial one in a Couette device. The Maxwell constant ranged from about 1.5×10−2 to about 4.5×10−6 cm2/dyne for freshly made sols and from about 8.0×10−2 to 2.9×10−5 cm2/dyne for the same sols when they were 29 days old. It is shown that the Maxwell constant for these sols was an exponential function of concentration and that the optical relaxation time and Maxwell constant could be related for them. Because the Maxwell constant is an exponential function of sol concentration, it is suggested that the expression for the rotary diffusion constant of an infinitely dilute sol of rod-shaped particles can be made applicable to more concentrated sols by multiplying it by the term (esC−1)/sC, where C is concentration and s is the slope of the curve relating sol concentration to Maxwell constant, to account for the change in particle interaction with change in sol concentration.

The viscosity and spectral transmission of these sols were also checked. It was found that the viscosity ranged from 1.0 cp for the most dilute sol to about 1.25 cp for the sol of concentration 0.1 volume percent. These sols were found to have a transmission which peaked at about 6800 A and dropped rapidly on either side of this value.
Negative Ion Formation in NO2 by Electron Attachment
Authors: Fox R. E.
Published: January 2005

Negative ion formation in NO2 by electron attachment is studied at low pressures as a function of electron energy in a mass spectrometer. The principle ion formed is found to be O− which onsets at 1.35±0.05 ev and whose apparent maximum occurs at 1.90 ev. Comparison of the peak shape with the electron energy distribution indicates the maximum cross section occurs within 0.1 ev of threshold. The NO2− ion whose maximum cross section is only about one-hundredth that for O− appears to have the same energy dependence. Crude estimates of the cross section for attachment yield order of magnitude values of 10−18 cm2 for O− and 10−20 cm2 for NO2−.
Proton Magnetic Resonance Spectrum of Propane
Authors: Whitman Donald R. , Onsager Lars , Saunders Martin , Dubb Hubert E.
Published: January 2005

Exact proton magnetic resonance eigenspectra of the spin Hamiltonian are calculated for a system containing one group of six identical protons and one group of two identical protons. The method of calculation considers each group of identical protons as a composite ``particle'' with fixed total spin, and does not require determination of the explicit form of the zero-order eigenfunctions. The calculated spectra are compared with experimental high-resolution spectra of propane at both 40 Mc and 60 Mc. Thevalues of p, the ratio of the spin coupling constant to the chemical shift, are found to be 0.415 and 0.277, respectively, at the two frequencies. The frequency-independent spin coupling constant is 7.26 cps.
Field Gradients at the Deuteron in Molecules
Authors: Bersohn R.
Published: January 2005

A survey of the observed quadrupole coupling constants of the deuteron is presented. It is concluded on the basis of calculations that the field gradients at hydrogen nuclei will be positive in almost all molecules. The simple wave functions greatly underestimate the field gradients of the bonding electrons. A good part, but not all, of the discrepancy, previously noted by White, can be removed with the use of a contracted charge distribution and ionic character. The wave function of Ellison and Shull gives a very bad description of the field gradients at the deuterons in D2O but the experimental data indicate the direction for future improvement. The field gradients at deuterons remain attractive quantities for characterizing the charge density in bonds involving hydrogen atoms.
Heats of Mixing in Liquid Alkali Nitrate Systems
Authors: Kleppa O. J. , Hersh L. S.
Published: January 2005

The enthalpies of mixing in binary liquid alkali nitrate systems have been measured, and are all negative. It is found that the magnitude of the molar mixing enthalpy (ΔHM) increases in a regular fashion with increasing difference in size between the two participating cations, according to the following approximate relation ΔHM≅−X(1−X)U[(d1−d2)/(d1+d2)]2.Here X and (1—X) are the mole fractions of the two components, U is the lattice energy of the mixture, while d1 and d2 are the interionic distances characteristic of the two pure components. The results are in accord with the view that in these systems the principal source of the enthalpy of mixing is the reduction in Coulombic repulsion between the second nearest neighbor cations. For binary systems with negative enthalpies of mixing of the order of RT there is evidence for short-range order among the cations.
Calculation of the Diamagnetic Susceptibility of N2
Authors: Hameka H. F.
Published: January 2005

The diamagnetic susceptibility of the nitrogen molecule has been calculated from wave functions that are constructed from gauge invariant atomic orbitals. The result is −13.539×10−6 which agrees satisfactorily with the average experimental value −13.3×10−6.
Choice of Parameters for the Hückel π-Electronic Structure of Furan: Tentative Extension to Pyrrole and Thiophene
Authors: Pilar Frank L. , Morris John R.
Published: January 2005

A comparison of the experimental bond lengths of furan with empirical bond length/bond energy relations for carbon-oxygen bonds leads to the conclusion that the ratio of the carbon-oxygen resonance integral to the carbon-carbon resonance integral of furan is between about 0.1 to 0.3. Use of this value along with a Coulombic integral parameter based upon the ultraviolet absorption spectrum of furan leads to a Hückel molecular orbital picture of the π-electronic structure of furan which is compatible with the known chemical reactivity of the molecule. The same approach is used to suggest resonance and Coulombic parameters for the Hückel molecular orbital treatment of pyrrole and thiophene. The treatment yields atom localization energies and para-localization energies consistent with the relative chemistries of furan, pyrrole, and thiophene.
Zero-Field Splitting of Molecular Zeeman Levels
Authors: McWeeny R.
Published: January 2005

Electron spin-spin coupling, responsible for zero-field splitting of Zeeman levels, may be discussed very generally by means of a ``coupling anisotropy function'' defined in terms of the components of the two-electron density matrix. The properties of this function are fully discussed elsewhere: the present note is concerned with zero-field splitting of triplet levels and with the series of approximations which lead from the general results to simple (orbital theory) approximations. A numerical calculation on the phosphorescent triplet states of naphthalene gives reasonable agreement with experiment.
Energy Levels for Internal and Over-All Rotation of Two-Top Molecules. I. Microwave Spectrum of Dimethyl Silane
Authors: Pierce Louis
Published: January 2005

A method is given for analyzing barrier-dependent ``tunnel effect'' splittings in rotational spectra of molecules with two equivalent tops. The perturbation treatment is an extension of the ``principal axis'' method for single-top molecules, and is limited to torsional states in which the two principal torsional quantum numbers are identical. Tables of perturbation coefficients are given from which the effects of top-top coupling on the rotational spectrum may be calculated. The microwave spectra of six isotopic species of dimethyl silane have been investigated in the region 8 to 25 kMc. Changes in moments of inertia with isotopic substitution yield the following structural parameters: SiC1.867±0.002 ACSiC110∘59′±10′SiH1.483±0.005 AHSiH107∘50′±20′CH1.095±0.005 AHCH108∘0′±20′,2θ=110∘59′±1∘, where 2θ is the angle between the symmetry axes of the methyl groups. From splittings in the rotational spectrum the angle 2θ is found to be 110°50′±20′. Analysis of splittings for (CH3)2SiH2, (CH3)2SiD2, and (CH3) (CD3)SiH2 indicates that coupling between tops is very small. Assuming no coupling, the barrier to internal rotation is 1647±3 cal/mole. From Stark effect measurements the dipole moment is found to be 0.75±0.01D.
Reaction of Cyclopropane with Iodine and Some Observations on the Isomerization of Cyclopropane
Authors: Benson Sidney W.
Published: January 2005

The kinetic and thermodynamic data of Ogg and Priest on the system I2+cyclopropane⇌ICH2CH2CH2I are reexamined. Using an entropy for ICH2CH2CH2I, estimated from additivity rules of 93.0±1.5 eu, and the experimental value of Keq, ΔH° is found to be −19.4±0.9 kcal. This gives Hf° (ICH2CH2CH2I) = 8.2 kcal/mole and the use of group additivity rules allow the values of ΔHf° for EtI and n—C3H7I to be fixed at −3.3±0.5 and −8.3±0.5 kcal/mole, respectively. For CH3I, ΔHf°=1.6±1 kcal/mole. The kinetic mechanism is also reexamined and from entropy and energy estimates for the free radical species, values of all of the rate constants are evaluated. These are in good agreement with values for similar reactions. It is proposed that the I2-catalyzed isomerization of cyclopropane proceeds through the step I+ICH2CH2CH2I→HI+ICH2–CH=CH2+I, followed by a rapid, atom-catalyzed reaction of allyl iodide with HI to give propylene. The rate constants for such a step are also in good agreement with those for similar reactions. Extension of the data to cyclopropane-propylene isomerization is made and it is shown that the most reasonable path involves the trimethylene radical as an intermediate. Its lifetime is, however, very short∼10−11 sec. Slater's model for this reaction is shown to be implausible. These data indicate an activation energy for the cyclization of the trimethylene free radical of about 8 kcal. This is reasonable only if the end CH2 groups in trimethylene are interacting via a ``bent'' bond. In such case the activation energy arises from the necessity for eclipsed configurations. A similar analysis is made for cyclobutane and the tetramethylene radical with compatible results. For cyclopropane the strain energy is 30 kcal and for cyclobutane 28 kcal.
Transferability of Urey-Bradley Force Constants. VI. The Silyl Halides
Authors: Overend John , Scherer James R.
Published: January 2005

Urey-Bradley force constants have been fitted, by least squares, to the observed vibrational frequencies of SiH3F, SiH3Cl, SiH3Br, SiH3I and their fully deuterated analogs. The force constants have been correlated with other molecular parameters and, in the case of the nonbonded hydrogen-halogen repulsions, have been discussed in terms of an inverse-power potential function.
Crystal Spectra of Metal Coordination Compounds. III. Nickel Complexes with Salicylaldehyde and Its Imines
Authors: Ferguson J.
Published: January 2005

Polarized single crystal absorption spectra are reported for three nickel complexes: bis-N-methylsalicylaldiminato-nickel (II), bis-salicylaldiminato-nickel (II), and diaquo-bis-salicylaldehydato-nickel (II). The analysis of the bands of an orthorhombic form of bis-N-methyl-salicylaldiminato-nickel (II) (described for the first time) results in the assignment of the two visible absorption bands to 1Ag→1B1g and 1Ag→1B3g, respectively. This assignment is discussed in relation to the simple crystal field model and a possible refinement of the model has been suggested. The analysis of the band observed with bis-salicylaldiminato-nickel (II) is consistent with the assignment of those in bis-N-methylsalicylaldiminato-nickel (II). The analysis of the visible absorption band of diaquo-bis-salicylaldehydato-nickel (II) shows that the theoretical assignment is incorrect although an unambiguous assignment cannot be made from the crystal spectrum.
Intensities of Infrared Bands of Some I2-Alkylbenzene Charge-Transfer Complexes
Authors: Ferguson E. E. , Chang Ike Y.
Published: January 2005

The intensities of the infrared bands corresponding to symmetric ring breathing and symmetric methyl stretching modes have been measured for charge-transfer complexes of iodine in benzene, toluene, the xylenes, mesitylene and 1,2,4 trimethylbenzene, durene, penta-, and hexamethylbenzene. The ring breathing mode intensity is found to decrease and the methyl stretching mode intensity to increase with methyl substitution. These results are interpreted in terms of a previously proposed ``electron vibration'' infrared absorption mechanism [E. E. Ferguson and F. A. Matsen, J. Chem. Phys. 29, 105 (1958); J. Am. Chem. Soc. 82, 3268 (1960)] extended to include π-electron interaction with methyl group electrons.
On the Nature of the Crystal Field Approximation
Authors: Herzfeld C. M. , Goldberg H.
Published: January 2005

A new method is developed for the treatment of molecular interactions, and is applied to a system consisting of a hydrogen atom in a 2p state and a hydrogen molecule in the ground state. The interaction of these two species is calculated using ordinary crystal field theory and also the new method. A comparison of the results shows some of the shortcomings of the conventional crystal field theory, and provides corrections to it. The new method consists of (1) expanding all electron terms of the total Hamiltonian for the system which involve interactions between the atom and the molecule, thus transforming the interaction Hamiltonian into sums of products of one-electron operators, and (2) of using properly antisymmetrized wave functions made up of products of atom and molecule eigenfunctions. The calculations show the effect of the neglect of overlap and exchange in ordinary crystal field theory.
Vapor Pressure of Silicon and the Dissociation Pressure of Silicon Carbide
Authors: Davis Stanley G. , Anthrop Donald F. , Searcy Alan W.
Published: January 2005

The vapor pressure of silicon and the dissociation pressure of silicon carbide have been obtained from total weight loss experiments with Knudsen effusion cells. Combination of the measured data with known entropies yields at 298°K for the heat of sublimation of silicon to silicon atoms 108.4±3 kcal and for the heat of the reaction SiC(s)=Si(g)+C(s) 126.0±3 kcal. From the pressure studies and from phase equilibria for the condensed phase silicon-carbon system, the heats of formation for both the cubic and hexagonal modifications of silicon carbide are concluded to be −15.0±2 kcal.
Pressure Induced Color Centers in CaF2 and BaF2
Authors: Minomura S. , Drickamer H. G.
Published: January 2005

The effect of pressure to 52 800 atm has been studied on x-irradiated CaF2 and BaF.. The three bands discovered by Smakula are little affected by pressure or bleaching. There are two new bands induced by pressure, which are greatly enhanced by any change in pressure. These bands show a marked blue shift with increasing pressure. Each can be bleached by light of its own frequency, and restored by reapplication of pressure. It is suggested that the pressure-induced bands are due to electrons associated with pressure-induced lattice defects, while the bands discovered by Smakula are associated with colloidal deposits or impurities.
Thermodynamic Theory of the Pair Correlation Function
Authors: Hart Edward W.
Published: January 2005

The thermodynamic description of inhomogeneous systems is adapted to a determination of the pair correlation function. The method is most effective for describing the correlation behavior near a critical point. The critical-point behavior is investigated for a simple model fluid of the van der Waal's type. A novel optical scattering phenomenon is predicted for the interface between two equilibrium phases for temperatures below but very near to the critical temperature. The effect of inclusions on critical point phenomena is noted.
Evidence of Trapped N Atoms in X-Ray Irradiated NaN3
Authors: King G. J. , Carlson F. F. , Miller B. S. , McMillan R. C.
Published: January 2005

Sodium azide irradiated with x rays at liquid-nitrogen temperature displays a power sensitive ESR spectrum of three equal lines of separation 6.2 oe. This spectrum is interpreted as N14 trapped in the crystal lattice.
Half-Crystal Energy Constants
Authors: Schmidt Hartland H.
Published: January 2005

Tables of the summation constants required for the calculation of surface energies of perfect half-crystals with Lennard-Jones types of inverse-power pair potential functions have been calculated using an IBM 709 computer. The tables cover simple cubic, face-centered cubic, body-centered cubic, simple hexagonal, and hexagonal close-packed structures with face plane orientations having Miller indices up to 5 in some cases. The inverse powers included in the tabulation extend from 5 (the lowest power for which these sums converge) to 13. The applications of these results to the calculation of grain boundary energy and spacing and to the estimation of surface distortion in half-crystals according to methods previously developed by the author are pointed out. The energies of hcp and fcc close-packed surfaces are compared as an example.
Condensation of Atomic and Molecular Hydrogen at Low Temperatures
Authors: Brackmann R. T. , Fite Wade L.
Published: January 2005

With the use of reflected modulated atomic-beam techniques, the reflection of hydrogen atoms and molecules at cold surfaces has been examined. It was found that at low temperatures (∼4°K) hydrogen atoms reflect as atoms with a very high probability. The reflection of hydrogen molecules is strongly dependent upon the amount of water vapor condensed on the target previously to or simultaneously with the H2. The fact that condensation of stable gases can be affected by simultaneous condensation of water vapor at temperatures exceeding the gases' normal boiling points leads to an application in the form of an extraordinarily inexpensive way to produce vacuums in the 10−5 mm Hg range.
Application of a Theory of Nonideal Solutions to Results of Ultrasonic Absorption Measurements
Authors: Goodman F. O.
Published: January 2005

It is shown that results of ultrasonic absorption measurements on solutions can sometimes be explained by application of a theory of nonideal solutions when the corresponding ideal-solution theory is inadequate. The results of ultrasonic absorption in tertiary butanol solutions in cyclohexane reported recently by R. Musa and M. Eisner are studied using a theory of nonideal solutions. This differs from the corresponding ideal-solution theory by the appearance of terms proportional to the derivatives of the ratio (k/l) of the relevant rate constants with respect to the concentration of the solute. In ideal solutions, these derivatives are zero. It is assumed that monomers and dimers are the only complexes present and it is concluded that a perturbation of the monomer-dimer equilibrium is responsible for the measured ``excess absorption.'' The nonideality of the solutions is discussed, and a ``nonideality coefficient'' is introduced. A comparison with the imperfect gas theory of Tabuchi is made.
The Second Law of Thermodynamics
Authors: Crawford Bryce , Oppenheim I.
Published: January 2005

Derivations of the mathematical statement of the second law of thermodynamics from the physical statements of Kelvin and Clausius are presented. Caratheodory's principle is obtained as a direct consequence of either Kelvin's or Clausius's statement.
Protection against Radiation Damage in Polymethylmethacrylate by High-Energy Electrons and by Ultraviolet Light
Authors: Gardner Donald G. , Epstein Lawrence M.
Published: January 2005

The protection against damage caused by ultraviolet light and 2-Mev electrons afforded polymethylmethacrylate by small amounts of such additives as pyrene, p-terphenyl, xylene, benzene, and lead stearate is examined. The results are discussed in terms of a model involving energy transport by both excited and ionized states.
Applicability of Approximate Quantum-Mechanical Wave Functions Having Discontinuities in Their First Derivatives
Authors: Hirschfelder Joseph O. , Nazaroff George V.
Published: January 2005

The method of convolutions is used to form smoothed functions from approximate wave functions which are discontinuous or have discontinuous first derivatives. As a parameter ε in the smoothed function decreases, the smoothed function approaches the approximate wave function. The expectation values for physical properties corresponding to the approximate wave function are defined to be the limit as ε approaches zero of the expectation values corresponding to the smoothed function. It is found that if the approximate wave function is discontinuous, the corresponding expectation value for the kinetic energy is infinite. Therefore, it seems unlikely that discontinuous approximate wave functions can ever be useful. However, if the approximate wave function is continuous but has a discontinuity in its first derivative, then, as a result of the discontinuity, there is a contribution δT̄12 to the expectation value of the kinetic energy. For a one-dimensional problem δT̄12=−(ℏ2/2m)ψ*(0) [ψ2′(0)−ψ1′(0)].Here ψ(0) is the value of the approximate wave function at the point zero where the discontinuity in its first derivative occurs, and ψ1′(0) and ψ2′(0) are the first derivatives of ψ taken from the left and from the right, respectively, at this point. Similarly, for an N-dimensional problem having a surface S12=0 over which the first derivatives of the approximate wave function are discontinuous, δT̄12= ∫ surfaceψ*[(∂/∂n) (ψ2−ψ1)]dS12.Here the ∂/∂n is the normal derivative with the normal pointed from region 1 towards region 2.
Effect of Molecular Oxygen on the Emission Spectra of Atomic Oxygen-Acetylene Flames
Authors: Krishnamachari S. L. N. G. , Broida H. P.
Published: January 2005

Studies have been made of the emission spectra (3000 to 6000 A) obtained from low-pressure atomic oxygen-acetylene flames diluted with varying amounts of molecular oxygen and molecular nitrogen. Added molecular oxygen greatly increased the OH emission while reducing CH and C2 emission. It also had an effect on the rotational intensity distribution of OH and on the vibrational intensity distribution of C2. Nitrogen addition greatly reduced the rotational and vibrational ``temperatures'' and decreased C2 emission relative to the other emitters.
Studies of Rates of Conversion and Populations of Conformations in Saturated Ring Compounds. III. NN′ Dimethyl Piperazine
Authors: Reeves L. W. , Strømme K. O.
Published: January 2005

At room temperature the two proton resonance signals observed in NN′-dimethyl piperazine are not of equal half-width. The signal caused by the ring methylene protons broadens as the temperature is lowered and below −40°C the spectrum is typical of an A2B2 case. These observations are indicative of fast interconversion relative to the axial-equatorial chemical shift between two identical chair forms of this molecule at +40°C and slow interconversion below −40°C. The A2B2 spectrum is partially analyzed, showing reasonable values for Je1a1, Je1e2, Je1a2, and the axial-equatorial chemical shift assuming only that the value of Ja1a2, is known. The energy barrier for interconversion is computed from the coalescence temperature and the exchange broadened single peak near the fast exchange limit. It is found to be 13.3±0.3 kcal. A comparison with earlier measurements in similar compounds is made. The N-methyl axial-equatorial motion is discussed.
Proton Magnetic Resonance Studies of Polycrystalline Uranium Oxide Hydrates. I. β-UO32H2O
Authors: Porte A. L. , Gutowsky H. S. , Boggs J. E.
Published: January 2005

The broad-line proton magnetic resonance spectra of polycrystalline samples of the compound formulated empirically as β—UO32H2O have been investigated in the temperature range 77°—350°K. The second moment of the absorption spectrum at 77°K indicates that some of the protons in the crystal are not present in water of crystallization and an analysis of the line shape shows that the compound is the trihydrate of pyrouranic acid, U2O5(OH)2·3H2O. The chemical properties of the compound are accounted for on the basis of this formula.
Transition Metal Binding in DNA Solutions
Authors: Eisinger J. , Shulman R. G. , Szymanski B. M.
Published: January 2005

Paramagnetic ions in water shorten the spin-lattice relaxation time T1 of the water protons. The effectiveness with which the relaxation takes place depends not only on the ion concentration, but also on the environment of the paramagnetic ion. In some cases where the paramagnetic ion is bound to a large molecule such as DNA, it shortens the proton relaxation time to a greater extent than when it is in solution. By measuring T1 by a pulsed nuclear magnetic resonance method, we have studied the binding of transition metal ions to DNA. We have obtained estimates for the number of available binding sites as well as information on the type of site which the various ions are bound to.
Effect of Oxygen on the Ultraviolet Spectra of Benzene
Authors: Lim E. C. , Kowalski V. L.
Published: January 2005

The ultraviolet spectrum of benzene induced by oxygen was studied in the wavelength range 2200–3000 A. From the experimental results obtained, the electronic absorption of this system is interpreted as a charge-transfer absorption induced during a chance contact between benzene and oxygen without formation of stable complexes. The general formula obtained by Tsubomura and Mulliken was used together with experimentally obtained energy of the charge-transfer state (about 5.6 ev) to calculate the intensity of the charge-transfer absorption borrowed from the 1A1g—1B1u and 1A1g—1E1u absorptions of benzene. The calculated intensity is in excellent agreement with experimental data, indicating that it is the interaction of the charge-transfer state with the benzene 1B1u and 1E1u states which is responsible for the observed intensity of the charge-transfer absorption.

Experimental evidence is also presented which indicates that the two previously observed weak absorptions in benzene at 4.2 and 4.9 ev, which several workers have conjectured might be the transitions to the higher triplet states, are not multiplicity-forbidden transitions. The absorption at 4.2 ev has been interpreted as due to an impurity and the absorption at 4.9 ev has been tentatively ascribed as due to a solvent effect whose nature is not yet understood.
Partition Function of Bulk Polymers. I
Authors: Boggs F. W.
Published: January 2005

This paper develops a theory which interrelates several aspects of the behavior of rubberlike materials through the extension of statistical mechanical treatments which have been developed for fluids.

An additional term of the partition function of bulk polymers is found. This term decreases as the temperature increases.

It has been possible partially to evaluate this added term by replacing important portions of it with thermodynamic expressions appropriate to liquids. This eliminates the necessity of attempting to evaluate series which would be difficult at low temperatures. In this way it is shown with a minimum of approximation how it is that the well-known and simple theory of rubber is valid at high temperatures and tends to show deviations as the temperature decreases. It further shows that the probability of finding a chain far removed from its most probable position decreases with decreasing temperature. It is hoped that these techniques can be used to explain some of the changes which occur in solid polymers as the temperature is lowered.
Enhancement of Rare-Earth Ion Fluorescence by Lattice Processes in Oxides
Authors: Van Uitert L. G. , Soden R. R. , Linares R. C.
Published: January 2005

In the absence of a suitable absorption band for a rare-earth ion, its fluorescence can be excited by ultraviolet radiation through interaction with the host lattice when the latter is excited near its absorption edge. Rare-earth ion fluorescence can be enhanced by localized lattice processes at frequencies lower than the absorption edge. Longer range effects occur as the absorption region of the crystal is approached. The enhancement due to these processes can be quenched by effects resulting from an increase in rare-earth ion content.
Critical Opalescence of Polystyrene in Cyclohexane : Range of Molecular Forces and Radius of Gyration
Authors: Debye P. , Chu B. , Woermann D.
Published: January 2005

Visible light scattered by binary mixtures of critical concentration of ordinary molecules at small temperature distances above the critical temperature shows an angular dissymmetry which can be related to the range of molecular forces. The theory of critical opalescence is extended to polymer solutions of high molecular weight for which an additional dissymmetry due to the extension of the polymer coil is observed. The range of molecular forces and the radius of gyration at the critical concentration can be determined simultaneously by measurements of the angular dependence of scattered intensity at different temperatures above the critical temperature. Results of experiments on a solution of polystyrene (Mn=2 820 000) in cyclohexane are reported.
Absorption Spectrum of Phenazine Single Crystals at 77° and 4.2°K in the Region of the n→π Transition
Authors: Hochstrasser Robin M.
Published: January 2005

The absorption spectrum of the long-wavelength edge of phenazine and 1,2- 3,4-dibenzphenazine has been measured at 77° and 4°K. A sharp band system is evident in crystals of each of these molecules. These systems have been assigned as n—π* transitions. For phenazine the band system involves a progression of a 398 cm−1 vibration frequency which has been attributed to a symmetric ring angular distortion. The band at 22 881 cm−1 was assigned as the allowed electronic origin of the transition (nπ*) B1u↔A1g. The spectrum contained a weak component which was attributed to a symmetry forbidden n→π* transition lying at less than 96 cm−1 below the allowed origin. The analysis of the spectrum suggests that the phenazine molecule is twisted in the nπ* excited state. The 0–0 band only appears in the b-polarized spectra and this indicates that crystal induced mixing with higher ππ* levels is occurring.
Virial Expansion of the Solution of the Kirkwood Integral Equation for the Radial Distribution Function of a Fluid
Authors: Stell George
Published: January 2005

The solution gK(r) of the Kirkwood integral equation for the radial distribution function of a fluid is expressed as a series in the density. This series is compared with the virial expansion of the exact radial distribution function g(r). It is shown that the term g2(r) proportional to the square of the density in the expansion of gK(r) differs from the corresponding term in the expansion of g(r). For the special case of hard-sphere particles g2K(r) is computed and used to obtain two approximations to the fourth virial coefficient of the equation of state. These results are compared with corresponding results for an approximate Kirkwood equation and for the Born-Green-Yvon and Percus-Yevick integral equations. The best agreement with exact theory is obtained from the Percus-Yevick equation; the poorest from the Kirkwood equation and the approximate Kirkwood equation.
Vibrational Relaxation in Carbon Monoxide by the Spectrophone Frequency-Response Method
Authors: Woodmansee W. E. , Decius J. C.
Published: January 2005

Although the spectrophone has been employed earlier to measure vibrational relaxation times by a phase-shift method, the use of a frequency-response (amplitude) method does not seem to have been previously reported. The limitations of microphone response to audio frequencies precludes the investigation of most gases by this procedure, but the expected long relaxation time in carbon monoxide suggested that a response loss might be observable for this molecule.

After some difficulties due to acoustic resonances in the spectrophone cell were overcome, a relaxation loss (relative to CO2) was found at room temperature for carbon monoxide, which corresponds to a relaxation time of approximately 2 msec at 1 atm. The result is compared with values found at much higher temperature by shock-tube experiments.

While the result for τ appears to be somewhat low in comparison with the shock-tube results, which may be due to traces of H2O or of H2 in the sample, the method appears to be useful in extending the range of measurements beyond that previously available by other techniques.
Metastable Simple Cubic Structures in Gold-Tellurium and Silver-Tellurium Alloys
Authors: Luo Huey-Lin , Klement William
Published: January 2005

By rapid cooling from the melt, single-phase simple cubic structures (one atom/unit cell) have been obtained for alloys in the ranges, 15–40 at.% Au;Te and 20–30 at.% Ag;Te. Type measurements and resistivity estimates indicate that the simple cubic phases are metallic. Lattice spacings of the simple cubic phases have been determined for single-phase and multiphase alloys. The 37.5 at.% Au;Te alloy is relatively more stable than the other metastable phases, as shown by annealing experiments.
Absorption and Fluorescence Spectra of Pr3+ in LaBr3
Authors: Wong Eugene Y. , Richman Isaac
Published: January 2005

The absorption and fluorescence spectra of 1% and 10% Pr3+ in LaBr3 were observed and an analysis carried out. The energy levels of these Pr3+ ions are very similar to Pr3+ in LaCl3, except that the centers of the J levels differ on the order of 102 cm−1. This corresponds to a change in Slater integrals of 0.5%. This change must be attributed to the different ligands in the two crystals. Two explanations are proposed, one based on a pure ionic model and the other on a model with small covalent bonding.
Gaseous Diffusion in Porous Media. II. Effect of Pressure Gradients
Authors: Evans R. B. , Watson G. M. , Mason E. A.
Published: January 2005

A previously proposed model for the diffusion of gases in porous media at uniform pressure is extended to allow for pressure gradients. The porous medium is visualized as a collection of ``dust'' particles constrained to remain stationary in space. As before, the entire range of intermediate mechanisms from the Knudsen to the normal diffusion region can be covered by varying the mole fraction of real gases. The effect of pressure gradients is to introduce into the fundamental kinetic theory equations both a pressure diffusion term and an external force term, which is needed to keep the porous medium from being pushed along by the pressure gradient. Somewhat surprisingly, there is a considerable cancellation of terms, and the final diffusion equation has the same form as in the uniform pressure case. No additional parameters beyond those necessary to define a diffusing system at uniform pressure are thus required to compute the diffusion rates when pressure gradients are present. The coefficients of the diffusion equation, however, now depend on position through their dependence on pressure, and the net flux J of all molecules is an undetermined quantity.

A complete solution requires also a forced flow equation giving J as a function of the pressure gradient. A forced flow equation is derived on the basis of the dusty gas model, but one parameter must be made disposable in order to compensate for the fact that the model permits only a diffusive mechanism for flow, never a viscous mechanism. Another forced flow equation is derived by analogy with Poiseuille flow, in which the porous medium is visualized as a group of capillaries. The two models are shown to be not inconsistent in viscous flow regimes, and complement rather than contradict each other. The Poiseuille model is mathematically very cumbersome, however, and has been used only at one especially simple point (at which J=0) to give an independent evaluation of the disposable parameter occurring in the dusty gas model. Agreement of the calculations with available experimental data is good. As in the uniform pressure case, the model does not give an a priori characterization of any porous medium, but rather permits prediction of the behavior of different gas mixtures under a variety of conditions on the basis of three parameters which can be obtained from only a few experimental measurements.
NMR of a Glycine Single Crystal
Authors: Webb W. E. , Moulton W. G.
Published: January 2005

The NMR absorption of a glycine single crystal was observed at 77° and 293°K for various orientations of the sample in the external magnetic field. On the basis of theoretical second moments computed from Van Vleck's equation it is concluded that the NH3+ group is a regular tetrahedron whose axis lies along the C–N bond. The N–H bond distance was determined to be 1.077±0.01 A.

It is concluded from the agreement between the computed and observed angular dependence of the second moments that the proposed model is correct.
Paramagnetic Term of the Susceptibility and Its Shift with Isotope in LiF
Authors: Russell Allan M.
Published: January 2005

The rotational magnetic moments μJ/ J have been measured for Li6F and Li7F in the same magnetic field. These measurements, when combined with the experimental value of μe2A for Li6F, yield a value for the internuclear distance which disagrees with the value obtained from vibrational spectra. It is proposed that the discrepancy is due to an error in assuming that the high-frequency or paramagnetic term χHF in the magnetic susceptibility is the same for each isotopic species. If the internuclear distances calculated from infrared spectra are assumed to be correct the high-frequency term is found to be χHF=(1.25±0.02)×10−5 erg G−2 mole−1.The isotopic shift ΔχHF is calculated separately and found to be ΔχHF=(5.0±0.5)×10−8 erg G−2 mole−1.This represents a decrease of 0.4% from Li6F to Li7F. A calculation of the electric dipole moment of Li6F from the same data yields, μe=6.40±0.04 D (v=0).