bluuebunny/crossref_metadata_2025_split huggingface dataset:
Time-Correlation Function of Molecular Random Motion and Shape of Spectral Bands
Authors: Shimizu Hiroshi 
Published: January 2005

It is shown that there is a close relation between the spectral density of Brownian motion and the band shape of a spectrum related to a general excitation-response process, and that time-correlation functions of a molecular system are obtained from the observed band shape of spectra. The correlation function for rotational Brownian motion of a molecular system is considered theoretically. Two limits of Brownian motion—the inertial limit and the Debye limit—are conveniently assumed. In the inertial limit, the correlation function is composed from two different parts, owing to the discrete nature of fluid in which the molecules are immersed. The first part of the correlation function gives the broadening of spectrum and the second part the narrowing. The relation between molecular motion and infrared spectrum is chosen as an illustration, because it provides simple correlation functions. Consequently, a theory of the band shape of infrared spectrum is presented in terms of the correlation function. The general features of the correlation function obtained from theoretical consideration are consistent with those obtained from the infrared spectrum of trans-dichloroethylene. In the Debye limit the effect of motion of neighboring molecules is considered. This leads a narrowing in the distribution of correlation times. The result is compared with the distribution function obtained experimentally through the Cole—Cole diagram.
The theory of nuclear spin relaxation is examined carefully. It is shown that Schwinger and Bloembergen's theory cannot be applicable to large molecules and that Bloembergen's treatment for the relaxation in the liquid state is not applicable to nonviscous liquid. A more general description is proposed.
Viscosity, Self-Diffusion, and Allied Effects in Solid Polymers
Authors: Bueche F. 
Published: January 2005

An attempt has been made to explain the observed viscous behavior of bulk polymers. It is found that the viscosity and diffusion may be represented by a theory which takes into account the coupling together of the molecules. Two equivalent treatments are given. One makes use of a segmental friction factor in the same manner as the common formulation of dilute solution viscosity of polymers. The second method uses the concept of segmental jumping. Since both are equivalent, an expression for the friction factor is found in terms of the segmental jumping frequency. Using this fact it is possible to calculate the segmental jumping frequency from bulk viscosity data. A simple application leads to the result that the jumping frequency is about 0.3 sec−1 at the transition temperature in polystyrene.
In addition a simple relation is found to hold between bulk viscosity and diffusion constant. The proportionality constant is easily evaluated and so one is now able to obtain self-diffusion constants directly from viscosity data.
Isotopic Composition of Oxygen in the Catalytic Decomposition of Hydrogen Peroxide
Authors: Dole Malcolm , Rudd DeForest P. , Muchow Gordon R. , Comte Charles 
Published: January 2005

The isotopic composition of oxygen liberated in the catalytic decomposition of hydrogen peroxide using MnO2, Fe2O3, colloidal gold, metallic platinum, and soluble catalase as catalysts has been measured. All the catalysts except catalase produced a measurable fractionation of the oxygen isotopes in the case of complete decomposition. A few rate experiments were also carried out, and the kinetics studied from the standpoint of isotope separation as a function of fraction of hydrogen peroxide decomposed. It is demonstrated that none of the liberated oxygen comes from the substrate water or from the potassium permanganate when hydrogen peroxide is oxidized. Observed fractionation factors are somewhat smaller than the maximum values calculated on the basis of Bigeleisen's equations. A minimum in the O18 percentage of the evolved oxygen in the case of the catalase experiments suggests that two mechanisms are operative for this type of catalysis.
The initial enhancement of the O18 percentage of the evolved oxygen over that in the peroxide remains unexplained.
Sedimentation Behavior of Flexible Chain Molecules: Polyisobutylene
Authors: Mandelkern L. , Krigbaum W. R. , Scheraga H. A. , Flory P. J. 
Published: January 2005

The sedimentation constants s0 at infinite dilution and the intrinsic viscosities [η] of five fractions of polyisobutylene have been determined in cyclohexane, a good solvent. Their osmotic molecular weights ranged from 3.1×104 to 1.4×106. Under the assumption that the effective hydrodynamic radii vary as the average linear dimensions of the molecule, f0/η0=P(〈r2〉)½ and [η]=Φ(〈r2〉)32/M, where f0 is the frictional coefficient, η0 is the viscosity of the solvent, 〈r2〉 is the mean-square end-to-end distance of the molecule, and P and Φ are constants. In confirmation, s0[η]⅓/M⅔ is constant throughout the molecular weight range investigated. Furthermore, Φ⅓P−1=2.5×106. The close agreement of this quantity with values for four other systems reported in the literature indicates that P, like Φ, is a universal constant for flexible chain molecules. It follows also that the observed proportionality of s0 (or of M/f0) to M0.42 instead of to M½ occurs because of intramolecular interactions which cause the molecule in solution to be expanded by a factor α which increases with molecular weight.
The above theory accounts for both the sedimentation and intrinsic viscosity behavior of flexible chain molecules in a satisfactory manner. Neither the Kirkwood-Riseman nor the Debye-Bueche theories succeeds in doing so.
Born Inelastic Differential Cross Sections in H2
Authors: Miller Kenneth J. , Krauss Morris 
Published: January 2005

First Born differential cross sections are calculated for inelastic electron scattering of 300-eV electrons off H2 for excitations from the ground electronic—vibrational state into the vibrational levels of the B, B′, C, D, and D′ Rydberg states. The initial and final state electronic wavefunctions were approximated by Hartree—Fock functions. In order to facilitate the calculation, the molecular orbitals were expanded in a linear combination of Gaussian-type atomic orbitals.
The variation of the electronic scattering amplitude was examined as a function of molecular orientation, internuclear separation, and scattering angle (or electron momentum transfer). It is shown that the use of the Franck—Condon factors to determine relative intensities for scattering into different vibrational levels yields errors of less than 20%, and hence these factors are a good approximation to the relative intensities.
The theoretical differential cross section for zero-angle scattering is in good agreement with the most recent experimental data, and transition moments extracted from electron scattering experiments within the context of the Franck—Condon principle are in agreement with the theoretical values.
Vapor Pressures of Isotopic Methanes—Evidence for Hindered Rotation
Authors: Bigeleisen J. , Cragg C. B. , Jeevanandam M. 
Published: January 2005

The liquid—vapor separation factors of CH3T and 14CH4 from 12CH4 have been determined over the temperature range 90°—120°K by the column-distillation technique. 14CH4 is less volatile than 12CH4 over the measured temperature range; CH3T shows the cross over at 103.9°K. The reduced partition function ratios derived from the elementary separation factors are lnfc/fg(14CH4/12CH4)=231/T2−1.42/T,lnfc/fg(CH3T/12CH4)=503/T2−4.83/T.The reduced partition functions of all the deuteromethanes and 13CH4 in the liquid and solid are derived from known vapor-pressure data. Comparison of the T−2 dependence of species of equal molecular weight but different moments of inertia, i.e., CH3D and 13CH4, and 14CH4, CH3T, and CH2D2, with model calculations leads to the conclusion that the rotation in methane is hindered both in the liquid and the solid.
Competitive Unimolecular Decomposition in Chemically Activated Radical Systems
Authors: Larson C. W. , Rabinovitch B. S. , Tardy D. C. 
Published: January 2005

The study of the competitive unimolecular decomposition of chemically activated alkyl radicals has been extended. Relative and absolute rates of decomposition for the series of radicals 3-methyl—butyl-2, 3-methyl—pentyl-2, 3-ethyl—pentyl-2, 2-methyl—pentyl-3, 2-methyl—hexyl-3, and 3-methyl—hexyl-3, each of which possess from two to four carbon—carbon rupture reaction channels, have been measured.
A quantum-statistical model for the absolute decomposition rates provided good theoretical agreement with the experiments. The measurement of relative rupture rates provided stringent conditions on the permissible values of the differences in critical energies ΔE0 for the competing decomposition modes. They also allowed the formulation of a consistent prescription for making the vibrational assignment for the decomposition complexes of the six radicals. The results are compatible with D0∘(CH3–H)−D0∘(C2H5–H)=5.7 kcal mole−1 and differences between critical heats of addition of methyl and ethyl radicals to olefins, Ec(Me, olefin) — Ec(Et, olefin), which vary systematically from −0.2 to 0.9 kcal mole−1.
Linear Relation of Temperature and Density at Unit Compressibility Factor
Authors: Holleran Eugene M. 
Published: January 2005

A linear relation is found for the experimental temperatures and densities at which the compressibility factor PV/RT equals unity. The two characteristic constants of the relation are evaluated for 12 gases for which appropriate data exist. The pertinent range of temperature and density for gases is from the critical temperature to the Boyle temperature, and from zero density to over twice the critical density. For one gas, Ar, the available data extend over this entire range and fit the linear law to within two parts per thousand. For CH4, Xe, and C2H4 over shorter ranges, the data are linear to within a few parts in ten thousand.
Implications of the relation are discussed, including its usefulness as a necessary condition for equations of state, as a basis for a corresponding states treatment, as a means for detecting and correcting experimental errors in PVT measurements, and in providing a possible insight into the nature of intermolecular forces.
Effect of Pressure on the Mössbauer Resonance in Ferrocene and Pyrite
Authors: Vaughan R. W. , Drickamer H. G. 
Published: January 2005

The effect of pressure to 200 kbars has been measured on the Mössbauer resonance in ferrocene and pyrite. For both compounds a large increase in s-electron density at the iron nucleus with pressure was observed. For ferrocene, calculations showed that the increase is primarily due to decrease in shielding of the 3s electrons by the 3d. To account for the change quantitatively it would be necessary to consider the change both in the occupation and radial extent (shape) of the 3d orbitals.
The quadrupole splitting in pyrites increased with pressure. Although both qlat and qval are probably important, the results could be accounted for in terms of the former component only.
For ferrocene a decrease in quadrupole splitting with increasing pressure was observed. A Wolfsberg—Helmholz type calculation gave a change in electric field gradient which accounted for the effect. The same calculation accounted for the change of the optical absorption frequency with pressure which was previously observed for the e2g→e2g* transition.
Computed Ground-State Properties of FH and CH
Authors: McLean A. D. , Yoshimine M. 
Published: January 2005

The accuracy of existing comprehensive calculations of wavefunctions of first- and second-row hydrides in close to the Hartree—Fock approximation is confirmed by performing test calculations, with larger Slater-function basis sets, on FH and ClH.
Dipole moments, quadrupole moments, magnetic susceptibilities, rotational g factors, forces on the nuclei, field gradients at the nuclei, and polarizabilities are then discussed and estimated from either computation alone, or by combining computed expectation values with observed properties. Excellent agreement between computation and observation is demonstrated for the quadrupole coupling constant for 35Cl and 37Cl nuclei in ClH. The following estimates of molecular properties not available elsewhere are made: rotational g factor is −0.033 for 19FH and +0.006 for 35ClH; diamagnetic anisotropy (ξ∥−ξ⊥) is −2.1 × 10−6 erg/G2·mole for FH, and −3.3 × 10−6 erg/G2·mole for ClH; eqQ(2H) = 0.34 Mc/sec in FH and 0.18 Mc/sec in ClH. For FH the axial components of the molecular polarizability tensor are (in atomic units) αzz=5.45, βzzz=−8.6, γzzzz=65, Az:zz=4.05, Bzz:zz=−32, 32Czz:zz=8.2. For ClH they are αzz=15.78, βzzz=−33, γzzzz=260, Az:zz=17.5, Bzz:zz=−125, 32Czz:zz=40.2.
Perturbation Theory of the Heats of Mixing of Fused Salts
Authors: Davis H. Ted , Rice Stuart A. 
Published: January 2005

A theory of the thermodynamic properties of molten salts including the effects of short-range attractive interactions has been developed. The analysis builds upon the work of Reiss, Katz, and Kleppa who showed that many of the thermodynamic properties of molten salt mixtures could be understood in terms of a model ionic melt consisting of rigid impenetrable ions interacting with a long-range Coulomb potential. The RKK theory is inadequate for the description of recent experimental measurements of the heats of mixing of salts whose short-range attractive interactions are expected to be significant. Most of the molten salt data of Kleppa et al. have been fitted to the following equation for the heats of mixing: ΔHm=x1,x2(a+bx1)δ122+x1x2c,    δ12=(λ2−λ1)/λ1,λ2,with xi the mole fraction of the ith component, a&lt;0, b&lt;0, and c&gt;0. The major contribution to a arises from Coulomb interactions, and is well accounted for by the RKK analysis which, however, does not completely account for b and gives c=0.
Using a perturbation analysis it is shown herein that the term c and part of b arise from short-range interactions between ions; the theoretical relationship deduced reproduces the observed composition dependence of the heat of mixing shown above. The qualitative deductions which can be made from the formal analysis are all in agreement with the available experimental data. It is also shown that there is a short-range potential contribution to the leading term (ax1x2) and explicit relationships for the coefficients a and b are obtained. A method of using the theorem of corresponding states to obtain information about the short-range coupling is suggested.
Vanishing First- and Second-Order Intramolecular Heavy-Atom Effects on the (π*→n) Phosphorescence in Carbonyls
Authors: El-Sayed M. A. 
Published: January 2005

The coupling schemes and matrix elements resulting from the first-order spin—orbit perturbation of the lowest n,π* triplet state in halogenated carbonyl compounds are examined. Because of the one-electron nature of Hs·o·, only seven of the 24 states resulting from one-electron transitions in X2CO, are found to perturb the 3A2(n,π*) state. Of these seven, only three states give rise to interactions involving the halogen atom: 1B2(n,σ2*) through two-center terms and small contribution of one-center term, 1A1(n,σ1*) through a small contribution of two-center term, and 1B1(σ1,π*) through three-center terms. Qualitative calculation indicates that of these three only the first interaction, when X=iodine, can be an order of magnitude larger than the one-center term on oxygen in H2CO. The absence of one- and two-center terms in the moment of the 1B2(n,σ2*)↔1A1 transition, however, reduces the importance of this state in inducing intramolecular heavy-atom effects.
Because of the one-electron property of the spin—orbit and vibronic operators, only two states, the 1B1(σ1,π*) and 1B2(n,σ2*), can be used for second-order (s.o. and vibronic) intramolecular heavy-atom perturbations. It is found that there are no intermediate states through which these states can couple with the emitting triplet state. These conclusions indicate that intramolecular heavy-atom effects on the π*→n phosphorescence radiative lifetime are expected to be small in X2CO or in any other carbonyl. It is pointed out that the large intramolecular heavy-atom effects observed for the π*→π phosphorescence is a result of the relatively small spin—orbit perturbation present in the parent heavy-atom-free molecule.
Photoionization of Propylene at 1236 Å. Reactions of C3D6+ with Added Alkanes
Authors: Gorden R. , Doepker R. , Ausloos P. 
Published: January 2005

C3H6–C3D6–O2 mixtures have been irradiated at 1236 Å (10 eV) in the presence and absence of an applied electrical field with the purpose of obtaining information about the ion—molecule reaction mechanism. On the basis of a number of observations, it was concluded that the product, propane, can be ascribed to the reaction C3mH6m++C3H6→C3mH6m−2++C3H8 (m≥2). When alkanes (RH2) whose ionization energy is larger than 10 eV are added to C3D6—O2 mixtures, the following H2−-transfer reaction occurs: C3D6++RH2→CD3CDHCD2H+R+ . Relative rates of the reaction of C3D6+ with various alkanes have been determined and compare favorably with values obtained in a recent radiolytic study in which cyclopentane-d10 was used as a source of C3D6+ ions.
The optimum experimental conditions, under which meaningful saturation ion currents can be obtained in the photoionization apparatus, are discribed. On the basis of measurements of the saturation ion current in NO and propylene at 1236 Å, values of 0.197 and 0.208 were obtained for the photoionization efficiencies of C3H6 and C3D6, respectively. The latter measurements made it possible to express the products in the number of molecules formed per ion pair as well as in the number of molecules formed per quantum absorbed.
On Brownian Motion in a Fermi Fluid
Authors: Davis H. Ted , Dagonnier R. 
Published: January 2005

Using the quantum-mechanical Boltzmann equation we study the motion of a heavy ion (mass M) moving through a Fermi fluid of light particles [mass m, γ=(m/M)½≪1] under the influence of an electric field. We find, contrary to the classical case, that the condition γ≪1 is not sufficient to ensure that the ion undergoes Brownian motion (i.e., its motion is characterized by a Fokker—Planck equation). The condition γξ≪1 must hold, where ξ2 is the ratio of the Fermi energy to the temperature. When ξ is too large the ion will suffer large momentum changes upon colliding with the fermions and hence its motion will not be describable by a Fokker—Planck equation.
In liquid 3He there is a temperature region (4°&gt;T&gt;1°K) in which a heavy ion experiences what we call quantum-mechanical Brownian motion; the Fokker—Planck equation still holds but the friction coefficient contains quantum-mechanical effects. Using our formula for mobility and the mobility data of Meyer we estimate the effective mass of an ion in liquid 3He to be about 20 times the mass of an 3He atom. This is in agreement with the recent measurements of Dahm and Sanders in liquid 4He. They have found the effective mass to be between 20 to 40 4He atoms. However, since only binary scattering events are accounted for in our mobility formula, its application to liquid 3He should be taken with reservation.
Thermal Energy Ion—Neutral Reaction Rates. I. Some Reactions of Helium Ions
Authors: Fehsenfeld F. C. , Schmeltekopf A. L. , Goldan P. D. , Schiff H. I. , Ferguson E. E. 
Published: January 2005

A flowing, steady-state afterglow system has been utilized to measure room-temperature ion—neutral reaction rates. A description of the apparatus and technique is given. Measured rate constants for He+ reactions with O2, N2, CO, NO, and CO2 are reported, as well as upper limits for the reactions of He+ with H2, Ne, and Ar, and an estimate for the reaction of He2+ with Ne and N2.
The reactions of He+ with O2, N2, CO, NO, and CO2 are all rapid, the rate constants all being ≈10−9 cm3 sec−1, implying essentially a reaction per collision.
Lattice Parameters of Nine Oxides and Sulfides as a Function of Pressure
Authors: Clendenen R. L. , Drickamer H. G. 
Published: January 2005

The lattice parameters of seven oxides and two sulfides have been measured as a function of pressure to several hundred kilobars. FeO, CoO, NiO, MnO, and MnS have the NaCl structure or slight distortions thereof. The data can be fit by a Born—Mayer equation. For FeO, CoO, and NiO the crystal-field stabilization term contributes 5% to 15% of the total attractive pressure. FeS2 (pyrites) has a cubic structure which can be related to the fcc lattice. Its compressibility is much less than MnS and more comparable to the oxides. The binding is appraently covalent.
SnO2, MnO2, and TiO2 all have the same tetragonal structure. For SnO2 and MnO2 the c axis actually expands with increasing pressure at low pressure, then passes through a maximum and ultimately contracts. The compressibilities of these two compounds are low at low pressure and increase at pressures beyond the maximum in c. TiO2 behaves more normally. It is apparent that central forces, and therefore ionic binding, contribute little to the cohesion of these crystals.
Proton Resonance Shift of Water in the Gas and Liquid States
Authors: Hindman J. C. 
Published: January 2005

Temperature-dependence measurements have been made on the chemical shift of the proton of a water molecule in the liquid state and in the gas state at varying pressure. The problem of relating these experimental data to the intermolecular forces leading to cohesion and to hydrogen-bond formation between water molecules is considered in detail. It is shown that a consistent treatment of the chemical shift, thermal, and dielectric data for water can be given based on a two-state model involving an equilibrium between a hydrogen-bonded ``icelike'' fraction and a ``monomer'' fraction whose interaction with the lattice arises entirely from London dispersion forces.
Using semiempirically derived values of the chemical shift and energy associated with the condensation of water vapor to ``monomer,'' the magnitude of the shift associated with the transformation to ice is calculated. It is then shown that, on the assumption that the hydrogen bond is electrostatic in character, the ``polar'' contribution to this shift can be related through the appropriate shielding equations to the dipole moment of the water molecule in ice. The magnitude of the dipole moment derived from these relationships is found to be in excellent agreement with values derived from dielectric data.
The possibility that the shielding changes may in part be due to processes other than the breaking of hydrogen bonds is considered. It is shown that the model leads to the conclusion that the chemical shift in the transformation of ice to water at 0°C could be entirely accounted for either by a stretching of the hydrogen bonds or a small amount of bending of the bonds. It is noted that if some bond breaking does occur, as required by the fact that water is a liquid, then the amount of stretching and/or bending will be limited.
Vibrational Relaxation of Hydrogen
Authors: Kiefer John H. , Lutz Robert W. 
Published: January 2005

The laser schlieren technique has been applied to a shock-tube study of hydrogen vibrational relaxation. Mixtures of 30%, 50%, and 70% normal hydrogen in argon have been investigated in the range 1100°—2700°K. The results yield an expression for relaxation in pure hydrogen, PτH2–H2 = (3.9±0.8) × 10−10 exp[(100.0±2.6) / T⅓] atm·sec (1100°—2700°K), and allow an approximate determination of the relaxation time for hydrogen dilute in argon, PτH2–Ar = 4.1 PτH2–H2 (1500°—2700°K).
These results are in adequate agreement with previous data and the theoretical calculations of Salkoff and Bauer. However, they are in serious disagreement with both the correlation of Millikan and White and the SSH theory.