bluuebunny/crossref_metadata_2025_split huggingface dataset:
Measurement of Inelastic Energy Loss in some Noble-Gas Ion—Atom Collisions at Kiloelectron-Volt Energies
Authors: Flinchbaugh David E. 
Published: January 2005

Large-angle collisions of Ne+ ions with Ar and Ne atoms, and protons with argon, were investigated, and the inelastic energy loss Q was measured as a function of incident energy, scattering angles, and state of ionization following the collision. Measurements for the Ne+-on-Ar case were made at 3-, 6-, 12-, and 25-keV incident energies, and both the recoil target particles and the scattered incident particles were studied at several angles between 15° and 85° with respect to the incident beam. The Ne+-on-Ne and H+-on-Ar data were taken at 25 keV over the same angular range. The kinetic energies and scattering angles were accurately measured, and this, together with the energy and momentum conservation equations, allowed determination of the inelastic energy.
The average value of the inelastic energy loss Q̄ is plotted vs recoil angle φ or vs scattering angle θ and a separate curve is obtained for each incident energy. However, when the various Q̄ values are plotted vs the calculated distance of closest approach r0, a universal curve is obtained for each ion—atom combination. The data points in each of the three cases studied appeared to fit best a curve giving Q̄ as a function of r0 to an inverse power. The protons especially showed deep penetration into the argon electron shell structure. Values of Q̄n, where n denotes the charge state of the collision product detected, are presented at each of several angles at each energy studied.
Rigid Disks at High Density
Authors: Stillinger Frank H. , Salsburg Zevi W. , Kornegay Robert L. 
Published: January 2005

A technique is developed for estimating the rigid-disk partition function near close packing, by evaluating the specific free-energy contributions from correlated motion of larger and larger sets of contiguous particles. In terms of the reduced density θ=A0/A (A0 is the close-packed value of the closed system's area A), the theory leads to an asymptotic series in the limit θ→1 for the Helmholtz free energy per particle, divided by kT, of the form: F/NkT∼2ln(λ/a)−2ln(θ−1−1)+C+D(θ−1−1)+···,in which C and D are appropriate numerical constants, λ is the mean thermal de Broglie wavelength, and a the disk diameter. It is shown that lattice defects cannot contribute to the above asymptotic series. The constant C is expressed as an infinite series whose leading term is the single-particle free area result [— ln (√3/2)], and whose successive terms account for high-compression cooperative motions involving ascending numbers of particles. An approximate value for C is obtained by computing all contributions for four or fewer correlated disks, with a resulting slight decrease below the free area value. The calculated C may be utilized along with machine-computed rigid-disk pressures on both fluid and solid isotherm branches to locate accurately the first-order phase transition by means of a Maxwell double tangent construction.
Some concluding remarks are directed to application of the present method to rigid spheres in three dimensions, where the high density stable crystal structure could be established by suitable extension of the present formalism.
Bis(1-Phenyl-1,3-Butanedionato) Vanadyl. I. Molecular and Crystal Structure of the cis Form
Authors: Hon Ping-Kay , Belford R. Linn , Pfluger C. E. 
Published: January 2005

The crystal structure of vanadyl bis(1-phenyl-1,3-butanedione) has been determined by two- and three-dimensional Fourier methods, and accurate atomic coordinates were obtained by three-dimensional least-squares refinements. The crystals are monoclinic with four molecules per unit cell. The space group is P21/c. The unit cell dimensions are a0=8.103,  b0=22.599,  c0=10.505 Å;  β=106∘47′.Both Cu Kα and Co Kα radiations were used for collecting the intensities. The over-all reliability factor (R) for 1894 independent reflections is 0.088.
The ligands are arranged in a cis configuration, and each phenyl ring is nearly coplanar with the chelate ring to which it is attached. The resulting balance of resonant and inductive effects appear in the bond distances and angles about the vanadium atom.
Reaction of Atomic Oxygen with Acetylene. II. Chemi-Ionization and Chemiluminescence
Authors: Arrington C. A. , Brennen W. , Glass G. P. , Michael J. V. , Niki H. 
Published: January 2005

The chemiluminescence and chemi-ionization resulting from the room-temperature reaction of atomic oxygen with acetylene have been investigated. The absolute intensity of chemiluminescent radiation and the over-all rate of chemi-ion formation have been measured and the relative concentrations of various individual chemi-ions have been observed with a T.O.F. mass spectrometer.
It has been shown conclusively from these measurements that chemi-ionization does not arise primarily from the reactions: CH (A 2Δ)+O=CHO++e−,CH (A 2Δ)+C2H2=C3H3++e−.It has been shown also that if ionization arises from the reactionCH (X 2π)+O=CHO++e−,a mechanism that has also received wide support, then the ground state CH (X 2π) molecule must be produced by some mechanism other than that producing CH (A 2Δ).
The CH (A 2Δ—X 2π) system was found to be the most intense feature of the chemiluminescent spectrum. Weak emission from the C2 Swan bands and from the CN violet system was also observed. The intensity of the weak OH emission was found to be consistent with it being produced by reactions with molecular oxygen. The CH emission was shown to arise from a complex series of reactions involving the participation of three molecules of acetylene and two atoms of oxygen. Two possible mechanisms for its production are discussed.
Thermochemistry of the Bromination of Chloroform and the Heat of Formation of the CCl3 Radical
Authors: Benson Sidney W. 
Published: January 2005

From Sullivan and Davidson's measurement of the equilibrium constant for Br2+CHCl3⇌ lim AHBr+CCl3Brat 442°K, and accurate CP° and entropies for the species involved, we find ΔSA°(298°K) = 2.2±0.2 gibbs/mole and ΔHA°(298°K) = −0.80±0.13 kcal/mole. Using known ΔHf° we calculate the unknown ΔH°f,298(CCl3Br) = −8.7±1 kcal/mole.
Analyses of the kinetic data together with reasonable estimates of S°(ĊCl3) and CP°(ĊCl3) permit assignments to be made of the Arrhenius parameters of the rate constants in the detailed mechanism. Analysis of the initiation and termination steps permit fixing limits on the activation energies for these steps as follows: Br+CHCl3⇌ lim 21HBr+ĊCl3ĊCl3+Br2⇌ lim 43CCl3Br+Br.E2=E3+0.22 kcal/mole≤2.0 kcal≈1.0±0.5 kcal/mole. These then lead to ΔH°f,298(ĊCl3) = 19.7 kcal/mole and DH°(CCl3–H) = 95.7±1.5 kcal/mole. Some other DH°(CCl3—X) bond strengths are listed.
Microwave Spectrum of Bromobenzene, Its Structure, Quadrupole Coupling Constants, and Carbon—Bromine Bond
Authors: Rosenthal Eli , Dailey B. P. 
Published: January 2005

As part of a study of the effects of substitution in the benzene ring, an experimental investigation of the microwave spectrum of bromobenzene has been carried out. The spectrum of four isotopically substituted molecular species of bromobenzene have been obtained: C6H579Br, C6H581Br, C6D579Br, and C6D581Br. Rotational and quadrupole coupling constants were obtained in each case.
The number of experimental rotational constants obtained was insufficient to permit a determination of the structure of the molecule without additional assumptions. The following structure is obtained for bromobenzene if hexagonal symmetry of the ring is arbitrarily assumed: rC–C1.4020 Å;rC–H1.0698 Å;rC–Br1.8674 Å.
The quadrupole coupling data for these molecules are consistent with a value of 1%—2% double-bond character for the C–Br bond.
Diffusion Along Dislocations
Authors: Luther Lars C. 
Published: January 2005

The Smoluchowski pipe model for diffusion along dislocations is modified so as to allow an exact solution of the two-dimensional diffusion equation. Using the continuously variable diffusion coefficient: D=D0/r2, where r is the radial coordinate perpendicular to the dislocation, rather than a step function, yields a diffusion profile proportional to: (D0t)−¼ exp[−2z/a(D0t)¼], a=Γ(¼)(2π)−½≃1.45 for large z, where z is the coordinate perpendicular to the surface from which diffusion occurs. Near the surface, where the Smoluchowski theory fails, the penetration is predicted to be anomalously high.
A characteristic diffusion coefficient for a grain boundary composed of parallel dislocations was calculated on the present model and found to be inversely proportional to the spacing of the dislocations.
Proton Dynamics in Hydrogen-Bonded Ferroelectrics
Authors: Imry Y. , Pelah I. , Wiener E. 
Published: January 2005

A comparison between infrared absorption and neutron inelastic-scattering measurements indicates the existence of a broad low-energy (around 400 cm−1) protonic level in KH2PO4 above the Curie point. This level is only weakly discerned in the ir but is seen quite clearly in neutron scattering. The mode is explained as resulting from splitting of the ground level of the proton in a slightly asymmetric double minimum potential well where tunneling of the proton takes place. The asymmetry is caused by the interaction between the different protons, and it changes slowly with time as the result of the collective motions of the protons. Prominent changes in ir spectra in the 400-cm−1 range were found on cooling through the Curie point, indicating the disappearance of the tunneling mode.
This picture allows a simplified treatment of the system, leading to the existence of two correlated phase transition points, and a negative thermal expansion coefficient of the H bond at temperatures between these points. The two transition points are identified as the Curie point and the melting or dissociation point of the crystal. The theory also suggests an increase in the dielectric constant as the melting point is approached, corresponding to the Curie—Weiss behavior as the Curie point is approached.
Vacuum-Ultraviolet Photochemistry. II. Solid- and Gas-Phase Photolysis of Methane—Water Systems
Authors: Stief L. J. , DeCarlo V. J. , Hillman J. J. 
Published: January 2005

The photolysis of the methane hydrate (CH4·6H2O) at −195°C at 1470 and 1236 Å has been investigated. Mixtures of methane and water in the gas phase have also been photolyzed at 1470, at 1236 Å, and in the region 1450–1850 Å. In both gas- and solid-phase photolysis, CO and CO2 are formed at 1470 and 1236 Å. CO2 is formed from CO, probably by the reaction OH+CO→CO2+H, which is shown to occur readily in the solid at −196°C.
In the photolysis of CH4·6H2O at −196°C, the hydrogen produced is mainly from the methane. Ethane is formed as well, and the product ratio CO2/C2H6 is a linear function of the ratio of the reactants H2O/CH4. Formation of CO2 and C2H6 by competitive reactions of CH2 with H2O and CH4 is suggested.
Similarity of results at 1236 Å to those at 1470 Å suggests that CH2 is present in both systems. Since photodecomposition of CH4 is negligible at 1470 Å, the production of CH2 at this wavelength is attributed to the occurrence of O+CH4→CH2+H2O with oxygen atoms being formed in photolysis of water.
On the Theory of Chemiluminescent Electron-Transfer Reactions
Authors: Marcus R. A. 
Published: January 2005

A mechanism is described for chemiluminescent electron-transfer reactions. It is shown that in the case of very exothermic homogeneous electron-transfer reactions, the intersection of the potential-energy surface of the reactants with that of electronically unexcited products occurs only at high energies. The rate of formation of unexcited products then becomes slow. A numerical estimate of this slowness is made using known homogeneous rate constants for ordinary electron-exchange reactions. An intersection occurs at lower energies when one of the products of a highly exothermic electron transfer is electronically excited, thereby reducing the exothermicity. The product may emit light or subsequently form a state that does.
A rather different situation is shown to occur at electrodes: the system can now reduce the ``exothermicity'' by having the electron transfer into a high unoccupied level of the conduction band or from a low occupied level of the latter. The large width of the conduction band in metals permits much latitude in reducing the exothermicity thereby.
These results are compared with present experimental findings that chemiluminescent electron transfers occur in solution rather than on electrode surfaces.
Infrared-Absorption Spectrum and Ferroelectric Behavior of Sodium Trihydroselenite
Authors: Khanna R. K. , Decius J. C. , Lippincott E. R. 
Published: January 2005

The infrared-absorption spectra of sodium trihydroselenite have been investigated in both the ferroelectric as well as the nonferroelectric phases. The analysis of the data suggests that in the ferroelectric phase the units HSeO3− and H2SeO3 are distinct with hydrogen bonds connecting their oxygens. The transition to the nonferroelectric phase results in the two units becoming equivalent, each behaving like a pyramidal SeO3= ion. This is explained in terms of the motion of the protons in a potential field which, in the ferroelectric phase, has an asymmetric double minimum. The transition to the nonferroelectric phase is accompanied by an even distribution of proton density along the bond length which, on the basis of our data, seems to be due to the potential field acquiring a single minimum.
Based on these results an attempt has been made to suggest a plausible switching mechanism in the ferroelectric phase and to correlate the spectral changes accompanying transition with the changes in the crystal structure.
Ground-State Energy of an Electron Gas in a Lattice of Positive Ions—Cohesive Energy of Alkali Metals and Alloys
Authors: De Leener M. , Bellemans A. 
Published: January 2005

Our previous calculations for the ground-state energy of a high-density electron gas in a lattice of positive point ions are extended to lattices of real ions with a core of bound electrons. The core effect on the electron gas is taken into account by the method of pseudopotentials put forward by Cohen and Heine. Both cases of lattices covered with one species and two species of ions are discussed.
The present model should give a rough picture of metals and alloys and was subsequently applied to alkali metals for which rather simple pseudopotentials have been proposed by Cohen. Numerical results obtained for the cohesion energy of the electron gas and the lattice of ions agree fairly well with the data of pure alkali metals. The heats of mixing of alkali metals have also been calculated with this model: They are very small and agree roughly with the order of magnitude of the experimental data.
Surface Rate Processes and Sensitivity of High Explosives
Authors: Chaiken R. F. , Cheselske F. J. 
Published: January 2005

The nature and rate of linear surface regression of TNT, RDX, Tetryl, and PETN have been studied utilizing a hot-plate pyrolysis technique over surface temperatures ranging as high as 500°C. The data, when compared to similar data for benzoic acid, suggest that the primary surface rate process appears to be an endothermic melt flow having an apparent activation energy suggestive of heat transfer and viscous flow as a rate controlling step.
These data, when used as a measure of surface heat dissipation, correlate very well with the measured values of impact sensitivity. Also, they offer an explanation for the fact that attempts to correlate impact and/or friction sensitivity with melting point alone could lead to misleading results when PETN and RDX are considered.
Quantum Chemistry of Electrode Processes. I. General Relations for Electron Exchange between Electrode and Electroactive Species under Equilibrium and Nonequilibrium Conditions
Authors: Schmidt Parbury P. , Mark Harry B. 
Published: January 2005

It is assumed in this paper that at the electrode—solution interface there is molecular order of the electroactive species resembling solid-state order. Specifically, it is assumed that next to the electrode is a layer of adsorbed neutral solvent molecules which are also ligands coordinated to the ions found in the interface. The mechanism of electron transfer from the electrode to the ion or the reverse from the ion to the electrode is assumed initially to involve a transition from either the electrode or the ion to the solvent molecule. This is followed by a transition of the electron from the solvent molecule to either the ion or the electrode. The two transitions involved in the net transfer of an electron across the interface are considered analogous to the charge-transfer mechanism of spectroscopy. The wavefunctions representing the system at the interface are then of the same form as the charge-transfer wavefunctions given by Mulliken.
By considering the radiationless transition probabilities for the electron transitions in the interface system at the electrode, it is found that the usual current expressions result. By imposing the condition of zero net current at equilibrium the Nernst equation results. By further considering the polarization of the electrode under nonequilibrium conditions as a perturbation of the energy levels of the system, it is found that with the proper identification of terms the current expression for the polarized electrode results.
The Temperature Dependence of the Solubility of Solid Nonelectrolytes
Authors: Hildebrand J. H. 
Published: January 2005

The solubilities of nonelectrolytes in solutions from which chemical interactions are absent, when plotted as logarithm of mole fraction vs logarithm of absolute temperature, yield practically straight lines except near the melting point of the solute. This offers a superior method of smoothing out solubility data and of predicting the temperature coefficient of solubility from a single point by comparison with neighboring lines for other solvents.
An explanation is given for this behavior.
The Microwave Spectrum of a Slightly Aspherical Top—The Structure and Dipole Moment of Sulfuryl Fluoride
Authors: Fristrom Robert M. 
Published: January 2005

The microwave spectrum of the slightly aspherical rotor, sulfuryl fluoride, has been investigated. Seven lines were found in the twenty to thirty thousand megacycle region. Six of these lines were assigned to J=1→2 and 2→3 rotational transitions of the molecule S32O2F2 and the other to the 111→212 transition of S34O2F2. These lines can be fitted to within the limits of experimental error (0.002 percent) with the following reciprocal moments of inertia: a32=5139.77 mc              a34=5139.77 mcb32=5077.81 mc              b34=5073.00 mcc32=5057.22 mc              c34=5052.51 mc
Structural parameters were determined from these moments and the assumption of C2v symmetry. The latter was confirmed by intensity measurements. S–O 1.370±0.01A      S–F 1.570±0.01A      O–S–O angle 129∘38′±30′ F–S–F angle 92∘47′±30′The S–O distance differs by −0.06A from the published electron diffraction value.
Measurements on stark lobes of the three 1→2 transitions of S32O2F2 gave a quantitative check of the assignment and a value of 0.228 Debye units for the dipole moment.
A Study of Selection Rules for Vibrational Spectra of Complex Crystals
Authors: Walnut Thomas H. 
Published: January 2005

Relations are obtained for the expression of the dipole moment and polarizability matrices for a particular transition in a crystal, in terms of corresponding expressions for molecular or ionic groups within the crystal. The results show that, to the degree of approximation used (quadratic terms in the dipole moment or polarizability expansion and cubic terms in the potential energy), the only cause for the appearance of bands which would be forbidden for a given uncoupled complex ionic or molecular group is the alteration of the normal coordinates of these groups by vibrations of neighboring groups. It is also shown that the bands of fully allowed first overtones and binary combinations of frequencies that are not degenerate or near-degenerate in a unit cell have a shape that is approximately given from the distributions of frequencies that arise from lattice coupling.
As an incidental result, the dipole moment matrix elements for the first overtones and binary combinations arising from the cubic terms in the potential energy are given explicitly.
Some Crystal Energetic Relationships in Oxysalts
Authors: Ramberg H. 
Published: January 2005

A regularity exists between the heat of formation of alkali and alkaline earth oxysalts and the acidity and basicity of the oxides involved. The more basic an alkali or an alkaline earth oxide, the larger is the exothermic heat of formation of its oxysalts from the component oxides. Likewise, the more acidic the nonmetal oxide, the larger is the exothermic heat of formation of its salts from the component oxides. Although this is expectable in a general way, the regularity and consistency of these rules are rather surprising.
The exothermic heat of formation from the oxides of different oxysalts of the same metal increases when the nonmetal changes through the sequences: B, C, N, and Si, P, S, Cl. This is explained in light of the increasing covalent character (or increasing polarization) of the oxygen-nonmetal bonds through the same series of elements.
The exothermic heat of formation of polymerized oxysalts from the component oxides (borates, silicates, phosphates, pyrosulfates) is larger per equivalent than for the corresponding simple oxysalts. This is qualitatively explained as a result of the oxygen-nonmetal bond being less polarized or more ionic in a polymerized salt than in the nonpolymerized salt with the same central atom in the oxyanion.
The heat of salt formation per equivalent increases numerically when the metal changes from Li to Cs, or from Mg to Ra. This is related to the increase of the crystal energy of the corresponding metal oxides.
Rotational Isomerism as a General Property of Alkyl Nitrites
Authors: Tarte P. 
Published: January 2005

The infrared and ultraviolet spectra of 15 alkyl nitrites were studied in the gaseous state. In the infrared, the O–N=O group is characterized by very strong absorption in the three regions 600, 800, and 1650 cm−1, corresponding to O–N=O bending, N–O stretching, and N=O stretching frequencies, respectively. The doubling of the characteristic frequencies and the temperature dependence of the bands of methyl nitrite are explained by rotational isomerism, which appears to be a general property of alkyl nitrites. The influence of the length, shape, and kind of the carbon chain on the frequencies and intensities of the characteristic bands has been studied. The intensity variation of the νN=O bands strongly suggests that the relative abundances of the two isomers vary widely from primary to secondary and tertiary nitrites, but depend only to a small extent upon the length and shape of the carbon chain. Application of this property to the diagnosis of primary, secondary, or tertiary alcohols is suggested.
The uv spectra consist essentially of two systems of diffuse bands (and not of one, as stated by previous workers), whose relative intensities vary in the same manner as the relative abundances of the two rotational isomers. The two systems of bands are accordingly assigned to these rotational isomers. This hypothesis has been checked by a study of the temperature dependence of the intensity of the bands.
Semilocalized Orbitals. IV. Relationship of n-Center Orbitals, Two-Center Orbitals, and Bond Properties
Authors: Mueller Charles R. 
Published: January 2005

The relationship between n-center orbitals, two-center orbitals, and bond properties is discussed from the standpoint of atomic, molecular, and semilocalized orbital theory.
The necessary restrictions on the transformation from the more general n-center to the two center orbitals is also discussed and a practical computational method for molecular problems is suggested.
The relationship of the atomic and molecular orbital theories of the excited electronic states of molecules is also investigated.