bluuebunny/crossref_metadata_2025 huggingface dataset:
Proton Spin Polarization of Water Adsorbed on Sucrose Chars
Authors: Krebs James J.
Published: January 2005

By saturating forbidden electron-nuclear double transitions in paramagnetic materials, it is possible to considerably enhance the nuclear polarization in a positive or negative sense. This effect has been investigated experimentally using the protons of water adsorbed on paramagnetic charred sucrose. The dependence of the enhancement on the saturating microwave power is derived for the case of overlapping allowed and forbidden transitions, and predicts a linear change in polarization at low power levels. The general features of the enhancement found are in agreement with those predicted by perturbation theory using a simple dipole-dipole electron-nuclear interaction. However, the plot of log (polarization change) vs log (power) has a slope of 0.82±0.04 instead of 1.0. In addition, the field separation between the points of maximum positive and maximum negative enhancement is too small in those chars for which inhomogeneous broadening is suspected.
Reactions of Active Nitrogen with Hydrogen Bromide, Bromine, and Ethylene
Authors: Milton Earl R. V. , Dunford H. B.
Published: January 2005

Measurement of the specific rate constant for the reactionN+HBr→NH+Brindicates that k is 3.8×10—14 sec—1 (molecules/cc)—1 at 40°C. Attempts to obtain complete turbulence of reactants at a pressure of 0.85 mm were unsuccessful so that diffusion techniques were employed. The homogeneous flame reaction accompanying the above reaction was too weak to define the reaction zone, so calculations were based on the reaction tube diameter and the critical flow rates of reactants at which the orange flame initiated by a wall reaction involving active nitrogen and bromine was prevented. Spectra of flames obtained from the N+Br2 and N+HBr reactions in a stirred-flow reactor indicate that NBr is the source of the orange flame in the latter reaction. The flow rates of atomic nitrogen were calibrated by chemical titration with ethylene. A conventional diffusion flame technique was used to obtain k=1.6×10—13 sec—1 (molecules/cc)—1 at 40°C for the reactionN+C2H4→HCN+CH3.
On the Luminescence Minimum in Certain Scintillator Solutions
Authors: Nosworthy J. M. , Magee John L. , Burton M.
Published: January 2005

Several scintillator solutions have been examined for the luminescence minimum previously reported for the case of Co60 gamma irradiated cyclohexane+benzene+p-terphenyl with oxygen present. The minimum is shown to be dependent on the nature of the solvents and of the quencher. A satisfactory interpretation of the data involves the notion of energy transfer from molecules of the less-efficient (``common'') solvent to the molecules of the more efficient (``better'') solvent and thence to the scintillator. The latter transfer appears to involve more than one molecule of the solvent. A suggested model of the quenching process explains the existence of two classes of quenchers, one of which does not give a minimum.
Growth of Whiskers by Chemical Reactions
Authors: Morelock C. R. , Sears G. W.
Published: January 2005

In the present paper the general conditions for the growth of whiskers by vapor deposition is considered. If several reactions are available to grow a given crystal phase, that reaction with the lowest entropy of reaction will allow the growth of near-perfect crystals, at the largest temperature difference between source crystals and growing crystals.
Proton Magnetic Resonances of Some Borazole Derivatives
Authors: Ito Kazuo , Watanabe Haruyuki , Kubo Masaji
Published: January 2005

The proton magnetic resonance spectra of ten borazole derivatives were recorded and assignments were carried out. The chemical shifts of BH and NH protons are close to each other, the values being nearly equal to the sum of the contribution of a diamagnetic ring current and the chemical shift of C=CH–C protons. The signals of NH and BH protons showed the partial collapse of multiplet structures due to quadrupole relaxation. BC2H5 protons gave a single sharp line instead of showing both methyl and methylene signals each split by I–I coupling. An explanation is given in terms of electronegativity considerations.
Proton Magnetic Resonance Spectra of Compounds of the Type X(C2H5)n. Relative Signs of the X-H Spin Coupling Constants
Authors: Narasimhan P. T. , Rogers Max T.
Published: January 2005

The high-resolution proton magnetic resonance spectra of phosphorus triethyl, tin tetraethyl, and lead tetraethyl have been studied at both 40 Mc and 60 Mc. The various spin-spin coupling constants (J) and the proton internal chemical shift (δ) values for these molecules have been obtained by an analysis of the spectra as A3B2 and A3B2X systems. (A denotes CH3 group protons, B the CH2 group protons, and X is a nucleus other than the proton with spin ½ such as P31, Sn117, Sn119, or Pb207.) In phosphorus triethyl it is found that JAX and JBX have opposite signs. The proton magnetic resonance spectrum of tin tetraethyl is a complex A3B2 type spectrum even at 60 Mc with ``satellite'' lines from naturally present Sn117 (C2H5)4 (7.67%) and Sn119 (C2H5)4 (8.68%) in the sample. Analysis of the satellite spectrum as an A3B2 type shows that JAX and JBX have opposite signs (here X=Sn117 or Sn119). The proton resonance spectrum of lead tetraethyl has been reinvestigated and it is found that the satellite lines due to Pb207 (C2H5)4 do not show any asymmetry, in contrast with earlier observations of Baker. Probable causes for Baker's results are given and it is shown theoretically and experimentally that such an asymmetry does not truly exist. The coupling constants JAX and JBX are found to have opposite signs in lead tetraethyl also.
Fractionation of Nitrogen Isotopes between Nitrosonium Salt Solutions and Nitrogen Oxides
Authors: Narten Alfred
Published: January 2005

Single stage enrichment factors α for the isotope exchange reaction of N15 between oxides of nitrogen and solutions of nitrosylsulphuric and nitrosylphosphoric acid have been determined. Single stage equilibration resulted in values of α that decrease from 1.046 for 1M to 1.013 for 10.2M sulphuric acid in the nitrosylsulphuric acid system, and from 1.042 for 4.7M to 1.005 for 14.8M phosphoric acid in the nitrosylphosphoric acid system.
Kinetics of Coordinate Bond Formation. V. Kinetics of the Reaction P(CH3)3+BF3
Authors: Kistiakowsky G. B. , Klots C. E.
Published: January 2005

The temperature pattern method in dilute spherical diffusion flames has been applied to the reaction of boron trifluoride with trimethyl phosphorus. The bimolecular rate constant indicates this to be the fastest association reaction yet studied with this technique. Expectations as to the effect of the reverse reaction on the temperature pattern are qualitatively confirmed. The origin of steric factors in coordinate bond formation is briefly discussed.
Electrical Resistivity of Liquid Sodium, Liquid Lithium, and Dilute Liquid Sodium Solutions
Authors: Freedman J. F. , Robertson W. D.
Published: January 2005

The three factors of atomic size, ion core potential, and charge, which contribute to the increment in electrical resistivity produced by solutes in metallic solutions, have been separated and experimentally evaluated in liquid sodium. The results may be expressed in a semiempirical relationship defining the increment in resistivity of a monovalent solution, Δρ=0.063 | Δ Atomic Number | +0.53 (ΔV/V)2, μohm cm/at. %, where ΔV/V is the fractional difference in atomic volume of solute and solvent and the first term involves the absolute value of the difference in atomic number of sodium and the solutes lithium, potassium, cesium, rubidium, silver, and gold.
Self-Diffusion in Linear Dimethylsiloxanes
Authors: McCall David W. , Anderson Ernest W. , Huggins Charles M.
Published: January 2005

The pressure and temperature dependences of the self-diffusion coefficients of the linear dimethylsiloxanes, containing from two to nine silicon atoms have been determined by the NMR spin-echo technique. Activation energies and volumes are presented as derived quantities; the constant-volume activation energy is estimated from these data. Extensive comparisons between the diffusion properties of the dimethylsiloxanes and equivalent hydrocarbons are made. From these comparisons, it is concluded that diffusion in siloxanes is controlled to a much larger extent by chain configurational effects. This concept is formalized by expressing the chain-size effects in an entropy of activation model.
Synthesis of the Cubic Form of Boron Nitride
Authors: Wentorf R. H.
Published: January 2005

A study of the formation of cubic boron nitride shows that the alkali and alkaline earth metals and their nitrides are effective catalysts for converting hexagonal boron nitride into cubic. The pressure and temperature required varies with the catalyst, and a minimum of about 45 000 atm and 1500°C has been found to be optimum up to the present time.
Proton Relaxation Times in Paramagnetic Solutions. Effects of Electron Spin Relaxation
Authors: Bloembergen N. , Morgan L. O.
Published: January 2005

The proton relaxation time in solutions of paramagnetic ions depends, among other factors, on the relaxation time of the electron spins, τs. It is shown that the latter, for ions of the iron group, is determined mostly by the distortion of the hydrated complex by collisions with other water molecules. The theory provides a quantitative explanation for the decrease in T2 in Mn++ (and other) solutions in very high magnetic fields. The experimentally observed field and temperature dependence of the proton relaxation times, T1 and T2, for ions of the iron group is compared with theory and the features which depend on τs are stressed.
Calculation of the Lower Excited Energy Levels of Helium
Authors: Hameka H. F.
Published: January 2005

The energies of the 11S, 21S, 23S, 21P, and 23P states of helium have been calculated according to a method due to Pluvinage. It was shown that the Coulomb electronic repulsion term may be replaced by an effective potential function that accounts for first-order electronic repulsion effects on the wave functions. The deviations between calculated and experimental energy values vary between 0.01 and 0.06 a.u.
Dimensional Change of Polypeptide Molecules in the Helix-Coil Transition Region. II
Authors: Nagai Kazuo
Published: January 2005

The mean-square end-to-end distance 〈R2〉 and radius of gyration 〈S2〉 are calculated for polypeptide molecules in the helix-coil transition region. The helical content, the sequence length distributions of helical and randomly coiled sections, etc., are also calculated for illustration. The statistical mechanical model on which the present calculation is based, is essentially equal to the second models in Gibbs-DiMarzio's and Zimm-Bragg's theories, respectively, though formulation is made on a more general model for the two purposes, i.e., for some convenience in calculating various quantities and for an examination of the degree of approximation of the above model. As a result, this model is found to be very satisfactory in spite of its simplicity. In order to calculate chain dimensions, two configurational models are examined. The one (model I), is somewhat rigorous, account being taken of the effects of bond lengths, bond angles, and hindered rotations. Two kinds of residues, i.e., those involved in helical sections, and those in randomly coiled sections, are distinguished by assigning different internal rotational potentials. The other (model II), is more approximate but more tractable. It can be obtained by replacing a helical section by a rod with an appropriate length and a randomly coiled section by an appropriate random flight chain. Numerical computations show that the two models give very close results for the infinitely long chain in the region where essential dimensional change occurs. By using model II, the effects of statistical mechanical parameters on 〈R2〉 are examined in detail. As a result, for example, it is shown that the larger the mean number of residues involved in a helical section becomes, the larger 〈R2〉 becomes, even if the helical content remains unchanged. For large N (e.g., N>300), as chain configurations go from randomly coiled to rodlike, 〈R2〉 and 〈S2〉 first decrease, pass through a minimum, and then increase until they reach the values for the perfect α helix. The appearance of this minimum is due to the considerably extended local configuration of randomly coiled residues. Namely, the appearance of a short helical section, turns the extended configuration to the folded one of the α helix and hence the polymer chain shrinks.
High-Speed Computations in Diffusion Kinetics. III. Solute Depletion in the Cylindrical One Radical-One Solute Model
Authors: Fricke Hugo , Phillips David L.
Published: January 2005

The earlier study [D. A. Flanders and H. Fricke, J. Chem. Phys. 28, 1126 (1958)] of the kinetic properties of a cylindrically symmetric one radical-one solute model was extended by taking account of the transient dilution of the solute which occurs during the reaction. The results of the computations are collected in a table from which, by interpolation IR the fraction of radicals recombining, can be obtained for any experimentally important values of the four dimensionless parameters which define the problem. Under conditions of practical interest the effect of solute depletion on IR is (a) appreciable only when the ratio of the rate constants of radical-solute and radical-radical reactions is above 0.1, and (b) only slightly affected by the diffusion coefficient of the solute. The role played by solute depletion is elucidated by graphs representing the transient course of the reactions.
Normal Coordinate Treatments and Calculated Thermodynamic Properties of Phosphoryl Chloride, Thiophosphoryl Chloride, and Phosphoryl Fluoride
Authors: Ziomek Joseph S. , Piotrowski Edward A.
Published: January 2005

The infrared and Raman spectra for phosphoryl chloride, thiophosphoryl chloride, and phosphoryl fluoride were collected and examined for the most probable values for the wave numbers, intensities, and depolarization factors. The data are as follows: The Raman displacements Δσ in cm—1, the relative intensities I, and the depolarization factors ρ are for POCL3: Δσ(1)ρ = 192.85 (8) 0.83, 267.39 (6) 0.64, 337.44 (7) 0.81, 486.24 (10) 0.05, 581.2 (3) 6/7, and 1289.9 (5) 0.04; for PSCl3: 172 (5) 6/7, 247 (7) 6/7, 247 (calculated) 430 (10) 0.1, 538 (1) 6/7, and 753 (1) P; and for POF3: 337 (w) 6/7, 476 (m) 6/7, 483 (from infrared) P, 875 (s) 0.05, 982 (vw) 6/7, and 1395 (m) 0.1. As for the infrared spectral data, those of G. Cilento et al., were used for PSCl3, and those of Gutowsky and Liehr were used for POF3. No published infrared spectral data were found for POCl3. Also normal coordinate treatments were conducted for POCl3, PSCl3, POF3, and PSF3 on the basis of a model having C3v symmetry. The normal coordinate treatments gave the listed wave numbers as fundamentals and lend support for the 247 cm—1 band for PSCl3 and 483 cm—1 band (observed in the infrared and assigned as fundamental by Gutowsky and Liehr) for POF3 as the missing Raman bands. Moreover, the F matrix elements obtained for these molecules were determined in such a manner that those potential constants for the PCl3 group had nearly the same values in both POCl3 and PSCl3, those for the PF3 group had nearly the same values in both POF3 and PSF3, the one for the PO group had nearly the same value in both POCl3 and POF3, and the one for the PS group had nearly the same value in both PSF3 and PSCl3. The potential constants determined had the following values in md/A: For POCl3, fPO=9.890, fPCl=2.466, fPClPCl=0.399, for PSCl3, fPS=0.030, fPCl=2.466, fPClPCl=0.399; for POF3, fPO=9.890, fPF=5.633, fPFPF=0.483, and for PSF3, fPS=2.9694, fPF=5.333, fPFPF=0.183. Finally, the values of the thermodynamic properties for these substances were computed for the ideal gaseous state using the rigid rotor harmonic oscillator approximation at 1 atm from 200° to 1000°K.
NMR Spectra of Propyl Derivatives
Authors: Cavanaugh James R. , Dailey B. P.
Published: January 2005

A perturbation treatment, carried to third order in the energies and first order in the intensities of the analysis of the propyl group spectra, is presented. Accurate values are given for the coupling constants and the chemical shifts of the common propyl derivatives, both for the pure compound and as extrapolated to infinite dilution in carbon tetrachloride.
Proton Chemical Shifts for the Alkyl Derivatives
Authors: Cavanaugh James R. , Dailey B. P.
Published: January 2005

The chemical shifts of a series of methyl, ethyl, propyl, and isopropyl derivatives have been studied in an effort to determine the distance and angular dependence of any contribution to the chemical shift arising from magnetically anisotropic substituent groups. It was found that electron withdrawal effects play a dominant role in determining the chemical shifts for methyl derivatives. The nearly exactly linear relation of the methyl shifts to electronegativity for the methyl halides seems to rule out any large influence due to magnetic anisotropy. The ethyl shifts were found to be determined by electron withdrawal effects plus a factor which acted equally at the α and β positions. It was found that this factor arises from the carbon-carbon bond. By assigning a chemical shift due to the presence of the C–C bond, which is dependent in size on the substituent attached to the α carbon, the apparently anomalous frequencies observed for the alkyl derivatives can be accounted for. A possible explanation for the C–C bond shift may be regular changes in the paramagnetic term in the Ramsey equation due to changes in the excitation energy denominator when a C–C bond replaces a C–H bond.
Calculation of Complex Equilibrium with an Unknown Number of Phases
Authors: Boll R. H.
Published: January 2005

An extension of Brinkley's generalized procedure is proposed for calculating the equilibrium compositions of complex systems in which several phases are possible but their actual number and identities at equilibrium are not known a priori. In contrast to other methods, the present method eliminates the trial and error associated with presence or absence of phases. Thus, little computational effort is required beyond that expended when the number and identities of all phases are known. The essential equations are given together with a description of the computational procedure.
Changes in the Electronic Transitions of Aromatic Hydrocarbons on Chemical Substitution. I. Perturbation Theory for Substituted Cyclic Polyenes
Authors: Petruska John
Published: January 2005

General formulas are derived by first- and second-order perturbation theory for the changes in the transition moment, transition probability, and frequency of aromatic cyclic-polyene transitions produced by ideal chemical substitutions. The changes are described in terms of the interactions of three kinds of prototype electronic states: carbon-ring states, substituent states, and charge-transfer states. The interaction of the ring states with one another is regarded as an inductive effect of substitution; the interaction with the substituent and charge-transfer states, as a conjugative effect. Using the symmetry properties of the prototype states and assuming that the interactions are caused by a sum of perturbation operators for the individual of substituents, it is shown how the changes depend on the nature, the number, and the positions of the substituents on the ring. Formulas pertaining to the singlet-singlet pi-electronic transitions in benzene are given.
Influence of the Molecular Environment on the Carbonyl Frequency. Electronic Calculation
Authors: Bratož S. , Besnainou Mme. S.
Published: January 2005

The KvC=O force constants of formaldehyde, acetaldehyde, acetone, glyoxal, p-benzoquinone, o-benzoquinone, and of chloroacetaldehyde have been determined by Pariser-Parr-Pople's SCF-MO procedure. The theoretical expression for the force constant corresponding to this theory is given. The KvC=O force constant is found to decrease in the order formaldehyde, chloroacetaldehyde, acetaldehyde, acetone; this is due to the corresponding decrease of the effective electronegativity of the carbonyl carbon atom. The KvC=O force constant decreases also in the series acetone, o-benzoquinone, p-benzoquinone, and in the series acetaldehyde, glyoxal; this is due to conjugation effects. The force constants calculated by this theory agree satisfactorily with the experimental values.
Thermoelectric Power of Silver Halides
Authors: Christy R. W.
Published: January 2005

Thermoelectric power measurements have been made on the systems AgCl+CdCl2, AgBr+Ag2S, and AgBr+CdS, as well as the pure silver halides, in the temperature range from 100° to 400°C. Silver metal electrodes were used. The behavior of AgCl and CdCl2 is similar to the previously investigated AgBr+CdBr2 system, except that the effect of the impurity is more pronounced in AgCl. The results of Cd-doping of AgBr and AgCl are analyzed according to the theory of Howard and Lidiard to give the concentration of Frenkel defects, the ratio of mobilities, and the quantities qi*+qv*, qi*+Tsi′, and qv*+Tsv′, where q* and s′ are the heats of transport and entropies of formation for the interstitials and vacancies. The results are in agreement with conductivity data, but the heats of transport are surprisingly large and temperature dependent. It is concluded that association between Cd+ + and Ag+ vacancies is negligible above 100°C, but that association between S— — and Ag+ interstitials, and between Cd+ + and S— —, is significant even at 400°C.
Wave Functions and Correlation Energies for F, F—, and Ne
Authors: Allen Leland C.
Published: January 2005

Hartree-Fock solutions have been obtained by the finite expansion technique and a comparison is made with other computational methods and results. Total energies, correlation energies, and one-electron parameters are presented as well as a tabulation of the radial functions in analytic form. The correct sign and order of magnitude of the fluorine electron affinity is predicted.
Anisotropic Hyperfine Interactions in the ESR Spectra of Alkyl Radicals
Authors: Cochran E. L. , Adrian F. J. , Bowers V. A.
Published: January 2005

We have studied the effect of anisotropic hyperfine interactions on the electron spin resonance (ESR) spectra of alkyl radicals trapped in polycrystalline matrices. The anisotropy broadens some or all of the hfs components, thus complicating the spectra. In alkyl radicals one has both isotropic and anisotropic hfs interactions with the α protons, but only an isotropic interaction with the β protons. Computed and experimental line shapes for the ethyl and propyl radicals are in qualitative agreement, provided that the hfs interaction is averaged over the various equilibrium orientations of the —CH2· group. This implies a rapid reorientation of the —CH2· group. It is noteworthy that when the two α protons are antiparallel the hyperfine anisotropy cancels and sharp intense hfs components result, while parallel orientations of the α protons give broad weak hfs lines. In particular, if the broad weak lines associated with the α proton hfs interactions are overlooked, the propyl radical spectrum appears to be a triplet, implying hfs interactions with the β protons only. In radicals where there is an odd number of α hydrogens (e.g. R′ — ĊH — R) there is no possibility of cancellation, and all the lines will be broad and weak. Our attempts to observe radicals of this type have been unsuccessful, most likely for this reason.
Tests for Chemisorption of Nitrogen on a Clean (100) Nickel Surface
Authors: Madden H. H. , Farnsworth H. E.
Published: January 2005

Tests have been made for chemisorption of nitrogen on the (100) surface of a nickel crystal, using low-energy electron diffraction and photoelectric work-function determinations. No chemisorption was observed after exposures as high as 10-3 mm Hg min at room temperature or at 350°C.
Approach to Thermodynamic Equilibrium
Authors: Mayer J. E.
Published: January 2005

The properties of a macroscopic classical system consisting of some 1020 molecules are determined by a probability density function W of the complete Γ space of moments and coordinates of all the molecules. This probability density function is that of the ensemble representing the totality of all experimental systems prepared according to the macroscopic specifications. The entropy is always to be defined as the negative of k times the integral over the distinguishable phase space of W lnWhΓ. However, the total probability density function W, even for a thermodynamically isolated system, does not obey the Liouville equation, ∂W/∂t=LW, since small fluctuations due to its contact with the rest of the universe necessarily ``smoothes'' W, by smoothing the direct many-body correlations in its logarithm. This smoothing is the cause of the entropy increase, and in systems near room temperature and above, in which there is heat conduction or chemical species diffusion, the smoothing keeps the true entropy numerically equal to that inferred from the local temperatures, pressures, and compositions. This, however, is by no means necessarily general. The criterion of thermodynamic isolation is not that the complete probability density function W is unaffected by the surroundings, but that reduced probability density functions wn in the Γ space of n=2,3,... molecules evolve in time as if the system were unaffected by the surroundings. This criterion is sufficient to give a mathematically definable method of ``smoothing'' the complete probability density function. The smoothing consists of replacing the direct many-body correlations in lnW by their average n-body values, n=2,3,..., such that the smaller reduced probability density functions wn are unaffected.
Relation of Perturbation Theory to Variation Method
Authors: Sinanoǧlu Oktay
Published: January 2005

The various order wave functions of the Rayleigh-Schrödinger perturbation theory can be obtained directly by solving certain differential equations or by minimizing equivalent variational expressions. These expressions are related to the ordinary variation method. The perturbation series is shown to result in a unique way from the minimization of larger and larger portions of 〈ψ, Hψ〉/〈ψ, ψ〉. In addition to several orders of perturbation, each step gives the exact remainders and upper limits to the energy. The approach suggests several ``variation-perturbation'' schemes.
Microwave Spectrum of cis 1-Chloro-2-Fluoroethylene
Authors: Howe John A.
Published: January 2005

The microwave spectrum of cis 1-chloro-2-fluoroethylene, CHCl=CHF, has been observed in the 15–25 kMc region for both chlorine species. Rotational constants for CHCl35CHF are a = 16,405.9, b = 3,756.05, and c = 3,052.67 Mc. Agreement of these and other data with values predicted from an assumed structure strongly suggests that the structure can be well represented as a composite of the known vinyl chloride and vinyl fluoride structures. Second-order quadrupole coupling theory is used to afford a direct measurement of χab; the nonzero elements of the tensor χ for the Cl35 species have the values χaa = —22.46, χbb = —10.88, and χab = ±56.7 Mc. These values show a 4% deviation of the C–Cl bond from cylindrical symmetry.
Derivation of the Tait Equation and Its Relation to the Structure of Liquids
Authors: Ginell Robert
Published: January 2005

The Tait equation — (dV/dP) = J/(L+P) has been theoretically derived from association theory. It is shown that the constant L, which is temperature dependent should also have a small pressure dependence. From the equation for the constants it is shown how the volume of holes in the liquid can be calculated. The number average degree of association of a liquid is defined and an equation for its determination is given. The general structure of liquids in light of this equation is discussed.
Configuration and Free Energy of a Polymer Molecule with Solvent Interaction
Authors: Fisher Michael E. , Hiley Basil J.
Published: January 2005

The lattice model of a polymer molecule with excluded volume and nearest-neighbor forces arising from polymer-solvent interaction is investigated by exact numerical calculation for short chains of up to about ten links. Extrapolation to large values of n, the number of links, is shown to be justified and enables the mean configuration, free energy, entropy, and internal energy to be evaluated as functions of the number of links and of temperature for both poor and ``super-perfect'' solvents. The mean square end-to-end distance is found to vary according to 〈rn2〉≈Anγ, in agreement with Wall et al., but γ=γ(η) is a decreasing function of the nearest-neighbor interaction parameter η=exp[—V0/kT]. For the three-dimensional simple cubic lattice γ(0)≃1.37, γ(1)≃1.20 and Flory's theta point, defined by γ=1, occurs at η≃1.48. For the two-dimensional square lattice γ(0)≃1.57, γ(1)≃1.47, and ηΘ≃2.0. The fractional variance of the distribution of rn2 is found to be appreciably smaller than the corresponding Gaussian value. Numerical data and graphs are presented for the free energy, entropy, and internal energy as functions of η.
Decomposition Rate of Nitric Oxide between 3000 and 4300°K
Authors: Freedman E. , Daiber J. W.
Published: January 2005

Time-resolved absorption spectra of shock-heated nitric oxide in the far ultraviolet have been taken using photoelectric detection. The decomposition rate of nitric oxide between 3000 and 4300°K was thereby measured. The initial rate was found to be the sum of the direct dissociation reaction, NO+Ar→N+O+Ar, with k=7×1012 exp(—150 000/RT) liters/mole sec, and the bimolecular reaction, 2 NO→N2+O2, with k=4.8×1020T—5/2 exp(—85 500/RT) liters/mole sec.
Electron Spin Resonance in a Gamma-Irradiated Single Crystal of Thiodiglycolic Acid
Authors: Kurita Yukio , Gordy Walter
Published: January 2005

The electron spin resonance of a gamma-irradiated single crystal of thiodiglycolic acid was measured at room temperature at 9 kMc. From the analysis of the anisotropy in the spectroscopic spliting factor and in the nuclear hyperfine interaction constants, a model of the free radical HOOC–CH2–S–CH–COOHis proposed. In this free radical, the electron spin density is mainly in a π orbital, about 60% of which is the p orbital of the CH carbon, 2% is the 1s orbitals of the CH2 hydrogens, and 22% is in the p orbital of the S.
Molecular Orbital Theory and Hyperfine Splitting in Electron Spin Resonance Spectra of Semiquinones
Authors: Vincow Gershon , Fraenkel George K.
Published: January 2005

Molecular orbital calculations of the unpaired electron density in a number of semiquinone ions have been made as a function of a range of values of the Coulomb integral αO for the oxygen atom and the resonance integral βCO between the oxygen atom and the carbon atom. The unpaired electron densities ρi were compared with the experimental hyperfine splitting constants ai arising from the proton bonded to carbon atom i by the use of McConnell's relation ai=Qρi. Excellent agreement is obtained for the proper choice of αO and βCO. In contrast to most experimental tests of molecular orbital theory, the agreement depends rather critically on the choice of these two parameters. The best values found for the parasemiquinone ions are in the neighborhood of αO≅αC+1.2 βCC and βCO≅1.56 βCC. The values of | Q | are close to 22.5 gauss. A different set of parameters is needed for the ortho-semiquinones. The molecular orbital calculation also fits the experimental splitting constants of the ring protons in the positions meta and para to the methyl group of the tolusemiquinone ion, but there is a large discrepancy at the position ortho to the methyl group. The results of detailed examination of a number of spectra of semiquinone ions are also reported.
Eigenfunctions for Integer and Half-Odd Integer Values of J Symmetrized According to the Icosahedral Group and the Group C3v
Authors: McLellan A. G.
Published: January 2005

Eigenfunctions of J2 for J=0, ½, 1···8, have been obtained and tabulated which are symmetrized according to the icosahedral group and the group C3v, in terms of eigenfunctions of J2 and Jz, referred to a fivefold axis of rotation as the z axis. The functions are symmetrized according to C3v in such a way that the symmetry operation of a 2π/3 rotation is represented by a diagonal matrix. The results have been applied to calculate the anisotropic magnetic splitting factors for the doublet states arising from the above symmetry.
n→π* Electronic Transition in Pure Alkali Nitrate Melts
Authors: Smith G. Pedro , Boston Charles R.
Published: January 2005

The lowest-energy transition (n→π*) of the nitrate ion was found to shift in energy and intensity in a systematic way over the series of molten alkali nitrates from LiNO3 through CsNO3. The energy E of the band maximum varied in a linear way with the cationic radius. At 365°C (extrapolated for CsNO3) E in electron volts was given by (3.81+0.33/r0), where r0 is the cationic radius (Ahrens) in A. The temperature dependence dE/dT was of the order of — 10—4 ev/deg and increased in magnitude with increasing cationic 1/r0. The f number (oscillator strength) decreased steadily along the series of alkali nitrates from 4.1×10—4 for LiNO3 down to 0.86×10—4 for RbNO3 and then rose again to 1.0×10—4 for CsNO3. The thermal coefficient (1/f) (df/dT) was in the range of 10—4 to 10—3 deg—1. The bandwidth changed by only a small amount for changes either in cation or in temperature. The origin of the observed shifts was considered in terms of interionic cohesive forces by application of the Franck-Condon and conservation of energy principles to a localized transition in a classical ionic melt. Digital computer procedures for profile analysis were described whereby an absorption band may be separated from an overlapping absorption edge.
Vaporization of Iridium and Rhodium
Authors: Panish Morton B. , Reif Liane
Published: January 2005

The vaporization of iridium and rhodium have been studied by Knudsen effusion and Langmuir evaporation techniques. The vapor pressure of iridium over the temperature range of from 2100° to 2600°K is represented by the equation: logpmm=10.46— (33980/T), and the vapor pressure of rhodium over the temperature range of from 2050° to 2200°K by the equation: logpmm=10.28— (28300/T). Third-law analyses of the data yield the following heats of vaporization:iridium, ΔH298=158.4±0.5 kcal/mole; rhodium, ΔH298=132.8±0.3 kcal/mole. Estimated boiling points for iridium and rhodium are 4800° and 3980°K, respectively.
Theory of Vibrational Relaxation in Liquids
Authors: Zwanzig Robert
Published: January 2005

A new formulation of the theory of vibrational relaxation, based on Zener's semiclassical approximation, is presented here. The relaxation rate is shown to be proportional to the spectral density of the force exerted on the oscillator by its environment. The isolated binary collision theory is derived, but only with the condition that the collision frequency is much smaller than the oscillator frequency. This requirement is not satisfied in a liquid; we conclude that Litovitz's application of the isolated binary collision theory to liquids is not justified. A possible relation between vibrational relaxation and the self-diffusion coefficient in a liquid is discussed.
Isotopic Separation Factor for the System Potassium Amalgam—Aqueous Potassium Hydroxide
Authors: Garretson H. H. , Drury J. S.
Published: January 2005

The isotopic fractionation of potassium between potassium amalgam and aqueous potassium hydroxide was measured at room temperature. The single-stage separation factor was 1.006±0.002 (95% C. I.).
Paramagnetic Susceptibility of Polycrystalline Praseodymium Metal
Authors: Arajs Sigurds , Colvin R. V. , Peck J. M.
Published: January 2005

The paramagnetic susceptibility of polycrystalline praseodymium metal has been measured between 300 and 1500°K. The measurements are in good agreement with the predictions of the Van Vleck theory of paramagnetism based on a localized f-electron model of noninteracting Pr3+ ions. By making a reasonable correction for the contribution of conduction electrons to the paramagnetism, a best fit to the experimental results is obtained by using a screening constant σ=34.
On the Theory of Helix—Coil Transition in Polypeptides
Authors: Lifson Shneior , Roig A.
Published: January 2005

The evaluation of the configurational partition function of a polypeptide molecule, with the internal rotation angles as variables, leads to an improved treatment of the phenomenon of helix-coil transition in polypeptide molecules. The conditional probabilities of occurrence of helical and coiled states of the peptide units are obtained in the form of a 3×3 matrix. The order of this matrix is the lowest possible for the model employed, and is derived by a logical procedure which serves to eliminate redundancies in the enumeration of states. The eigenvalues of this matrix yield the various molecular averages as functions of the degree of polymerization, temperature, and molecular constants. Explicit formulas are given for the degree of intramolecular hydrogen bonding, average number of helical sequences, and the distribution of their lengths, as well as the number average and the weight average of these lengths.
Crystal Field Parameters for Erbium in Er (C2H5SO4)3·9H2O
Authors: Erath Edward H.
Published: January 2005

Intermediate coupling wave functions and eigenvalues for f11 were used to compute the effective operator equivalent factors for the free-ion levels of erbium. The Stark splitting of the ground level 4I15/2 was used in a first-order perturbation calculation on the ground state to determine the crystal field parameters. The parameters that fit the experimental data best are; 〈r2〉A2=125.80, 〈r4〉A4=—31.06, 〈r6〉A6=—81.19, 〈r6〉A66=387.19. The parameters were used to calculate the Stark splitting of the free-ion levels and the results compared with experimentally observed values for ten levels. For the 46 Stark levels involved the calculation predicts the splitting with an average deviation of 3.4 cm—1.
Theory of the Diamagnetic Susceptibilities of the Alkanes
Authors: Hameka H. F.
Published: January 2005

A general theory of the diamagnetic susceptibilities of the alkanes is developed. It is found that the molecular susceptibilities are obtained as sums of contributions from the 1s electrons of the carbon atoms, from the various C–C and C–H bonds, and from interactions between various pairs of adjacent C–C and C–H bonds. It is possible to express the theory in a semi-empirical form so that all susceptibilities of the alkane molecules are expressed in terms of three parameters. For the most reliable series of experimental data, the susceptibilities of 24 different hydrocarbons may be described by these parameters within an accuracy of 0.5%. Theoretical values of diamagnetic susceptibilities are given for 54 alkane molecules, namely for all isotopes up to and including octane, for the normal alkanes from nonane to hexadecane and for a few other molecules for which experimental data have been reported. The accuracy of the theoretical values is compatible with the accuracy of the measurements.
Effect of Electron Energy on Some Electron-Impact Processes
Authors: Meyerson Seymour
Published: January 2005

Decomposition processes induced by electron impact have been inferred from appearance potentials and from isotopic distributions of fragment ions in mass spectra of labeled compounds. Implicit in such inferences is an assumption that the paths by which the fragment ions are formed are the same near the appropriate appearance potentials as at the higher electron energies usually employed. For five ions that were the subjects of earlier studies—C7H7+ from two deuterated p-xylenes and C5H5+ from two deuterated toluenes and a deuterated benzyl chloride—isotopic distribution has been found to be essentially independent of electron energy. These results support the assumption made in earlier studies.
Interaction of Hydrogen and of Nitrogen with a Molybdenum Ribbon
Authors: Pasternak R. A. , Wiesendanger Hans U. D.
Published: January 2005

Adsorption and desorption studies—by flash-filament and ion gauge techniques—gave information on surface coverages, sticking probabilities, atom formation, and surface mobilities for the interaction of gases with a molybdenum ribbon. For hydrogen, saturation surface coverages were independent of pressure (10—8—10—5 mm Hg), within experimental errors, but depended strongly on temperature (225°—500°K). Adsorption below 320°K proceeded in two steps. Two layers were successively adsorbed and completed at 320° and 225°K, respectively; each contained close to two hydrogen atoms per surface molybdenum atom. The sticking probability was 0.35; it remained constant during the formation of the first layer. At about 700°K, no measurable amounts of hydrogen were retained on the ribbon surface, but the kinetics of atom formation above 1200°K suggested that traces of hydrogen might be adsorbed at much higher temperatures. Finally, adsorbed hydrogen was readily replaced by other gases, such as nitrogen, even at room temperature. For the adsorption of nitrogen, the saturation surface coverage decreased only about 30% from 225°—710°K; its value at room temperature was about one nitrogen atom per surface molybdenum atom. The initial sticking probability, in the same temperature range, decreased from 0.7 to 0.2.
Binding Energies of Alkali Halide Molecules
Authors: Rothberg G. M.
Published: January 2005

The repulsive part of the energy of interaction of an alkali ion and a halogen ion may be written fe—z/r, where f and r are constants appropriate to the ions and z is the internuclear distance. In alkali halide crystals and monomers, f and r may be determined empirically, but in the case of the dimers the necessary data are lacking. In this paper the repulsive energy is examined qualitatively with use of the Thomas-Fermi model, and an approximation is found for the dimer constants that enables accurate calculations to be made of the binding energies of the dimers.
Line Shape of Ultraviolet Absorption in Solid Noble Gases
Authors: Meijer Paul H. E.
Published: January 2005

The absorption of ultraviolet radiation in solid noble gases shows lines that are a few hundred inverse centimeters broad. An attempt is made to explain and calculate the width and shape of these lines on the basis of a tentative curve of energy versus configuration. It is shown that the width has the proper order of magnitude. The line shape can be easily calculated at the short wave length end. It should show an exponential tail. If we inspect the expression for small values of the energy, we find a rapidly rising exponential, which will give rise to a smeared-out edge appearance. The line will have a nonsymmetrical shape.
Phosphorescence Spectra of Acenaphthene at Low Temperatures
Authors: Zmerli Adnan
Published: January 2005

The phosphorescence spectra of acenaphthene, both of single crystals and of solutions in different solvents (polystyrolene, benzene, or E.P.A.), were photographed at low temperatures. At 4° and 77°K unpolarized spectra of the crystal were obtained using a phosphoroscope, and at 20°K the polarized spectra along the three crystallographic axes had been photographed without the phosphoroscope. Some peculiarities linked to the existence of two different sets of molecules in the unit cell have been observed. Two progressions, here called ``normal,'' connected to each set of molecules have been distinguished in the 4° and 77°K spectra but not in the 20°K spectrum. The interval between the corresponding bands of the two progressions is 28 cm—1. In the 20°K spectrum two new series, here called ``nonnormal,'' and which appear also in the 77°K spectrum have been observed. An attempt of interpretation of these ``nonnormal'' series has been advanced.
NMR Spectra of Vinyl Chloride and the Chloroethylenes
Authors: Whipple E. B. , Stewart W. E. , Reddy G. S. , Goldstein J. H.
Published: January 2005

The NMR spectra of vinyl chloride, the three dichloroethylenes, and trichloroethylene have been obtained and analyzed. Three deuterated species of vinyl chloride were used to facilitate the analysis and to obtain all the C13–H couplings in this molecule. The C13–H couplings were also obtained for the other chloroethylenes. The NMR parameters are compared for the entire series of compounds, and it is shown that a definite parallelism exists between the chemical shifts and the C13–H couplings. The results are discussed in terms of the inductive and mesomeric properties of the chlorine substituent.
On the Kinetic Theory of Dense Fluids. VII. The Doublet Distribution Function for Rigid Spheres with an Attractive Potential
Authors: Allnatt Alan R. , Rice Stuart A.
Published: January 2005

A new integro-differential equation for the doublet distribution function of a model dense fluid is derived and solved. In this model, the intermolecular pair potential is represented as a rigid core plus an attraction. Interactions involving rigid cores are handled as in the theory of the dense rigid-sphere fluid and attractive interactions are handled as in the Fokker-Planck theory. The resultant doublet distribution function is compared with the singlet distribution function calculated for the same model.
Surface-Catalyzed Excitations in the Oxygen System
Authors: Mannella Gene , Harteck Paul
Published: January 2005

A luminosity is produced over Ni maintained at approximately 20°C in a stream of O atoms. Spectroscopic investigation shows the strongly forbidden b 1Σg+ — X 3Σg— atmospheric system and A 3Σu+ — X 3Σg— Herzberg system of the O2 molecule plus four strong heads of the (0, 0) band of the OH A 2Σ+ — X 2Π interaction. Certain spectral features in the region of the (0, 0) atmospheric band could not be resolved for positive identification but are suggested to be the vibrational-rotational bands of OH. The Herzberg and atmospheric bands appear to be primary products of the surface catalysis while the OH molecule can be either a surface product or the result of chemical reactions of certain excited species present.
Electron Spin Resonance of γ-Irradiated Glycylglycine
Authors: Katayama Mikio , Gordy Walter
Published: January 2005

The electron paramagnetic resonance spectra of a gamma-irradiated single crystal of α-glycylglycine have been measured at 9, 24, and 29 kMc/sec for various orientations of the crystal in the external magnetic field. From analysis of the spectroscopic splitting factors and the hyperfine interaction constants, the free radical produced by gamma irradiation is found to be:[Complex chemical formula]The electron spin density on the —ĊH carbon atom is evaluated as approximately 0.75.
Infrared Spectra of NaOH Above and Below the Melting Point
Authors: Greenberg Jacob , Hallgren L. J.
Published: January 2005

The absorption spectra of NaOH and mixtures of NaOH in NaNO3, in NaNO2 and in LiCl–KCl eutectic mixture have been observed. The shift in the band position for NaOH as the temperature is varied is explained on the basis of hydrogen bonding in the melt.
Solid-State Vibrational Spectra of the Methyl and Methyl-d3 Halides
Authors: Jacox Marilyn E. , Hexter Robert M.
Published: January 2005

The vibrational fundamentals of solid CH3Cl, CH3Br, and CH3I and of their fully deuterated counterparts have been examined at 77°K under high resolution. CH3Cl35 has been synthesized and its ν3 spectrum compared to that of ordinary CH3Cl, permitting the assignment of the CH3Cl35 and CH3Cl37 contributions in the ν3 multiplet structure. The relative intensities of absorption in 1:1 CH3X:CD3X solid solutions have been measured to test the relationship between splitting, frequency, and absorption intensity predicted by the dipolar correlation model. The test proved to be insensitive. A study of the ν3 absorption of each component in CH3Cl:CD3Cl solid solutions throughout the concentration range has shown that multiplet splitting persists at concentrations as low as 1%.