bluuebunny/crossref_metadata_2025_split huggingface dataset:
Stretching Force Constant of the Carbonyl Bond in Unconjugated Ketones
Authors: Halford J. O. 
Published: January 2005

The secular equation derived for the normal frequencies of a Y-shaped C2CO model can be used with fair accuracy to obtain the carbonyl bond force constant from the measured carbonyl frequency of any symmetrical ketone if the carbon-carbon force constant and the bond angles are known or can be reasonably assigned.
The narrow spread of carbonyl frequencies observed for unconjugated ketones, with assumed ``normal'' angles and carbon-carbon force constant, indicates a nearly constant carbonyl stretching force constant in the range 10.2±0.3 (×105 dynes/cm). This value should be equally reliable for unsymmetrical unconjugated ketones.
In formaldehyde, the calculated force constant is usually above 12.5 units.
Vibration Spectrum of Graphite and Boron Nitride. I. The Two-Dimensional Spectrum
Authors: Newell Gordon F. 
Published: January 2005

A detailed analysis of the vibrational modes of graphite and boron nitride, which are sufficiently similar that they can conveniently be considered together, begins here with a study of the effects of interactions only between particles in the same layers of the lamellar structure.
The secular equation for any lattice vibration problem can be written as a sum of contributions arising from the interactions between various groups of particles. After describing a system of notation which will eventually be used to describe all types of interactions, that part of the secular equation resulting only from nearest neighbors is derived. The frequencies and the spectral densities of all frequency branches are obtained for a system with only these forces. Because of the existence of some low-frequency branches, it is necessary to also consider second nearest neighbor forces, even though they may be relatively much weaker, in order to obtain a complete realistic description. The frequencies of all modes of the system with both types of forces are then analyzed. Part of the spectrum can still be found in closed form; other parts can be found only approximately.
This analysis gives a fairly complete description of a ``coarse grain'' frequency distribution which can, in principle, be used to describe the thermodynamic behavior of the system at all but the lowest temperatures where the interactions between layers become significant. The principle limitation on its usefulness is at present due to the sizable number of as yet unknown parameters necessary to describe the system numerically.
On the Pi-Electron Approximation and Its Possible Refinement
Authors: Lykos Peter G. , Parr Robert G. 
Published: January 2005

The pi-electron approximation is defined to be the approximation in which the following two restrictions are imposed upon the total approximate electronic wave functions for some group of molecular states:
(I) The wave function for each state satisfies the sigma-pi separability conditions: (A) the wave function has the form Ψ = [(Σ) (II)], where (Σ) and (II) are antisymmetrized functions describing the so-called sigma and pi electrons, respectively, and the outer brackets connote antisymmetrization with respect to sigma-pi exchange; (B) each of (Σ), (II), and Ψ is normalized to unity; (C) each of (Σ), (II), and Ψ is well-behaved.
(II) The sigma description is the same for all states.
Imposition of these restrictions is shown to be sufficient to validate the customary procedure in which the pi electrons in a molecule are treated apart from the rest.
A formula is given for the pi-electron Hamiltonian to be used when the pi-electron approximation is invoked. Present day pi-electron theories are examined, and lines for carrying out improved calculations are suggested. An iterative procedure is proposed for treating both sigma and pi electrons wherein first a sigma function is assumed (which defines a ``core'' in the field of which the pi electrons move), then a pi function is computed (which defines a ``peel'' in the field of which the sigma electrons move), then a new sigma function is computed, and so on.
Certain generalizations of the quantum-mechanical argument are made which give it wider applicability, and several illustrations are drawn from pi-electron theory and elsewhere.
9.6-Micron Band of Telluric Ozone and Its Rotational Analysis
Authors: Kaplan L. D. , Migeotte M. V. , Neven L. 
Published: January 2005

The 9.6-micron band of atmospheric ozone has been investigated by means of high resolution measurements of the solar spectrum from the Jungfraujoch in Switzerland. A rotational analysis confirms its assignment as the v3 fundamental and results in the following values for the vibrational frequency and rotational constants: ν3=1042.16 cm−1;  A=3.502 cm−1,  B=0.4401 cm−1,  C=0.3883 cm−1.
The decrease of all three rotational constants relative to the ground-state values suggests an appreciable Coriolis interaction with the v1 fundamental.
Spectra and Quantum States of the Europic Ion in Crystals. II. Fluorescence and Absorption Spectra of Single Crystals of Europic Ethylsulfate Nonahydrate
Authors: Sayre Edward V. , Freed Simon 
Published: January 2005

From the polarization properties of the fluorescence spectrum of single crystals of europic ethylsulfate nonahydrate it was possible to determine the multipole character of transitions, the energies and quantum nature of the seven levels of the ground state multiplet of the europic ion, and the group character of the sublevels into which these states are split by the crystal field. Such an analysis was made of all pure, uncoupled electronic transitions in the fluorescence spectrum. The analysis revealed that the rare earth ion is predominantly perturbed by a field of D3h symmetry, arising from the water molecules of hydration immediately surrounding it. Upon this field is superimposed a weaker one of lower symmetry, C3h, arising from the lattice as a whole. All transitions involving a change of J of one appeared as magnetic dipole radiation. All others appeared as forced electric dipole transitions, including one which would have been fully allowed as a magnetic dipole transition.
A similar analysis of the absorption spectrum in the near ultraviolet was only partially successful because of the superposition of the split levels of some of the upper states. It was in accord with the analysis of the fluorescence spectrum and from it was determined the multipole nature of the transitions and the quantum nature of some of the more isolated upper states.
Wavelength Formulas and Configuration Interaction in Brooker Dyes and Chain Molecules
Authors: Platt John R. 
Published: January 2005

The zero-order wavelength of absorption, λI, of a conjugated chain of N bonds with all bonds equal is λI=Nλc+λL+λR,where λc is a universal constant, about 500 A per bond, and λL, λR are end-group corrections. The corresponding energy, EI, is modified in second order by configurational mixing of the ground state with a certain excited state, to give within experimental error the observed transition energy E=[EI2+(bL−bR)2]12.The derivation is a simplified adaptation of the ideas of Brooker, Herzfeld, and Sklar. The end-group basicities, bL and bR, or stabilizations of alternative resonance structures, locate the electron density maxima in the chain and determine the bond density alternations and bond length alternations that probably produce the mixing. They are additive and consistent for over 50 end groups and can be derived theoretically in many cases. Their dependence on chain length and solvent is shown. Substituent groups have two parameters, λ, b, as in aromatic ultraviolet spectra.
The changes in transition band widths, vibrational structure, and intensity in changing solvents are accounted for. The strong convergence of polyene series spectra and the nonharmonic spacing of their higher states is attributed to their large b-values, about 20 kK. The corresponding mixing of states is related to the probable character of the excited state wave functions and to the probable strong alternation of polyene bond lengths even in long chains.
Calculation of Vibrational Relaxation Times of the Chloromethanes
Authors: Tanczos Frank I. 
Published: January 2005

The Schwartz, Slawsky, and Herzfeld method for the calculation of vibrational relaxation times of gases has been extended in its application to polyatomic molecules. A general method is developed for the calculation of the effective relaxation times and the associated constants of the sound velocity relaxation equation. Calculations have been made for the bimolecular collisions of methane and the chloromethanes involving changes of one, two, and three quanta. A normal coordinate treatment is used to obtain the atomic vibrational amplitudes. The effect of an intermolecular potential function, embodying a dipole interaction term, is included for the polar molecules of this investigation.
Calculated results are compared with experimental data. For CH4 and CH3Cl the calculations agree well with experimental results. For CH2Cl2, CHCl3, and CCl4 the calculated relaxation times are higher than selected experimental values by factors of 8–9. For CH2Cl2, CHCl3, and CCl4 two major relaxation times are calculated. In the case of CH2Cl2 the two relaxation areas have been observed. The experimental data on CHCl3 and CCl4 remain inconclusive in respect to the two predicted relaxation areas. Collisions involving three quanta are shown to be important for CH2Cl2, CHCl3, and CCl4.
Photolysis of Dimethyl Peroxide
Authors: Takezaki Yoshimasa , Miyazaki Teruhisa , Nakahara Noriko 
Published: January 2005

Dimethyl peroxide has been photolyzed in vapor phase by 2537 A-light under various peroxide pressures at temperatures from 21 to 60°C, and for various light intensities at 30°C. The over-all rate was measured manometrically.
The reaction is self-inhibiting and is also greatly inhibited by a small amount of formaldehyde. The initial rate is expressed by AI+BI½[CH3OOCH3]½ (A≪B and I is absorbed light intensity), and it tends to 3I when formaldehyde is added sufficiently. Carbon monoxide, methanol, and formaldehyde were found in the reaction product. The amount of hydrogen was quite small in the normal run and also in the run where much formaldehyde was added. Based on these results the following mechanism has been proposed: CH3OOCH3+hν→2(H+HCHO),H+CH3OOCH3→CH3OH+CH3O,{CH3O+CH3OOCH3→CH3OH+CH3OOCH2,CH3OOCH2→CH3O+HCHO,CH3OOCH2+CH3O→CH3OH+2HCHO.
From the temperature coefficient of the rate, Ea+Eb—Ec= 5.8 kcal, the difference of activation heats, has been obtained; the numerical value is supposed to be the upper limit of Eb.
Scattering of High Velocity Neutral Particles. VIII. H–He
Authors: Amdur I. , Mason E. A. 
Published: January 2005

Total collision cross sections have been measured for hydrogen atoms with energies between 700 and 2100 ev, scattered in room temperature helium. The results have been analyzed to obtain potential energy information for the interaction between a hydrogen atom and a helium atom. The potential function, which may be represented by V(r)=3.75×10−12/r3.29 ergfor r between 1.16 A and 1.71 A, gives values which agree with those calculated quantum mechanically by Mason, Ross, and Schatz.
The H–He potential has been combined with a potential previously obtained for He–He to obtain a function which, it is suggested, represents the repulsive interaction between two hydrogen atoms. The derived function is in fair agreement with theoretical calculations of Hirschfelder and Linnett for the repulsive 3Σ state of the hydrogen molecule.
Intensity and Line-Width of the 15-Micron CO2 Band, Determined by a Curve-of-Growth Method
Authors: Kaplan Lewis D. , Eggers David F. 
Published: January 2005

The intensity of the 15 μ band of CO2 has been redetermined by a curve-of-growth method, utilizing simple formulas derived for the absorption coefficient of the Q branch. The value obtained is 240 cm—1 per cm at S.T.P., some 25 to 30% higher than the results of the Wilson-Wells method. Extrapolation methods in general can lead to considerable underestimation of intensity, especially when applied to bands containing narrow Q branches.
The nitrogen-broadened half-width at one atmosphere and 298K is 0.064 cm—1.
Color Centers and Luminescence in Single Crystals of Lanthanum Trichloride Containing Dipositive Europium
Authors: Gruen Dieter M. , Conway John G. , McLaughlin Ralph D. 
Published: January 2005

The edge of the fundamental absorption band in pure LaCl3 is at about 2250 A. There is no change in the absorption spectrum of pure LaCl3 in the range 2250 to 25 000 A on exposure at room temperature to 107r of gamma rays from a Co60 source. The crystals do not luminesce after such treatment.
In contradistinction, LaCl3 containing small amounts of europium exhibits a blue luminescence and thermoluminescence when exposed to ultraviolet or gamma radiation. The luminescent properties are profoundly influenced by long continued gamma irradiation. In addition, color centers are formed which absorb visible radiation.
Chemical as well as paramagnetic resonance experiments show that all of these effects are due to the presence in the LaCl3 lattice of dispositive europium. There are at least three different color centers giving rise to three overlapping absorption bands which decay thermally with different rates. The maxima of the absorption bands are at 8000, 6500, and 5500 A. Studies with polarized light show that the color center transitions are all electric dipole in nature and are highly anisotropic. The most intense band has been tentatively identified with an F-center-like s→p transition.
Experiments on the thermal decay of the color bands and the glow curve of the crystal indicate that an intimate relationship exists between the color center and the luminescence phenomena.
It is suggested that when these crystals are irradiated, dipositive europium loses an electron to become tripositive, the electron being captured by an anion vacancy to form a color center. On thermal freeing of the electron, return to the ground state is accompanied by the emission of visible radiation.
Electronic Spectrum and Structure of Azulene
Authors: Pariser Rudolph 
Published: January 2005

A previously given theoretical method is applied to the azulene molecule. π-electron energies, transtion moments, dipole moments, charge distributions, and bond orders are calculated for the ground state and for the lower singlet and triplet excited states.
The same detailed procedure which had previously given good results for the polyacenes is used here. Configuration interaction is included for all singly excited configurations. Two parallel calculations, one starting with conventional Hückel MOs and the other with perimeter MOs, are carried through.
Hückel MOs lead to numerical results in good agreement with available experimental spectral data. In this connection some previous assignments are confirmed and some new ones are proposed. For the π-electron dipole moment for the ground state, one calculates 1.88 D with Hückel MOs and 3.36 D with perimeter MOs; the experimental value is 1 D.
One may conclude that the present procedure gives results in substantial agreement with experiment provided that good MOs, e.g., Hückel MOs, are employed. For computation of excited state energies it is essential to include interaction among nearly degenerate configurations. More extensive configuration interaction, however, appears to improve the transition energies and especially the transition moments and dipole moments.
Application of Probability Theory to Explosive-Ignition Phenomena
Authors: Parlin Ransom B. , Giddings J. Calvin 
Published: January 2005

The problem of explosive ignition concerns itself both with the probability of occurrence of local energy fluctuations and with the transition of these disturbances into a combustion or detonation wave. The former concept does not appear to have been comprehensively discussed; a treatment of this process is presented here for the case of fluctuations due to frictional forces.
The theory is applied to several cases of impact ignition, both with and without grit particles and it is found to be in good agreement with experiment. Information is obtained through application of the theory concerning the nature and location of the local disturbances responsible for ignition.
Infrared Absorption of Lanthanum, Scandium, and Indium Borate and the Force Constants of Borate Ion
Authors: Steele W. C. , Decius J. C. 
Published: January 2005

The infrared absorption spectra of LaBO3, InBO3, and ScBO3 have been observed as crystalline powders in the wavelength range from 7 to 20 microns. The borates had a B10/B11 ratio varying from the natural abundance (18/82) up to about 96/4. The four fundamental frequencies for B10 fell within the ranges, ω1 = 939, ω2 = 740–790, ω3 = 1265–1330, ω4 = 606–675, all in cm—1. The totally symmetric frequency, ω1 is observed only in LaBO3, which has less than threefold site symmetry, unlike the other two salts.
The GVF force constants have been calculated and are compared with those of BF3. A very strong specific coupling of the out-of-plane bending mode (ω2) is observed in LaBO3, but the fine structure is not well resolved, and only a rough estimate of the coupling constant and dipole derivative can be made.
Effect of Pressure on Dielectric Properties and Volume of 1-Propanol and Glycerol
Authors: Gilchrist A. , Earley J. E. , Cole R. H. 
Published: January 2005

Dielectric constants and loss have been measured to pressures of 1000 kg/cm2 at audio- and radio-frequencies from 212 to 240°K for glycerol and 124 to 210°K for 1-propanol. Compressions to 1000 kg/cm2 have been measured to room temperature.
The increases in static dielectric constant are less than predicted from density increase alone, and the differences are discussed in terms of molecular compression and liquid structure effects. Larger increases of relaxation time with pressure are found at lower temperatures. Constant volume relaxation times do not conform to a simple rate law, and cannot be explained by activation energies depending only on volume. Glycerol shows small, temperature independent, percentage volume decrease with pressure over the whole range; 1-propanol becomes much less compressible at low temperatures.
Equations for a Lattice Gas. I. One-Component Systems
Authors: Levine Howard B. , Mayer Joseph E. , Aroeste Henry 
Published: January 2005

An expression is developed for P/kT for a lattice gas with an arbitrary lattice as a power series in the nearest neighbor interaction parameter, λ, with the coefficients functions of the activity, z. This result is applied in some detail to the cubic close packed lattice, for which expressions for the number density, ρ, and the probability of finding a cell adjacent to a filled cell also filled, ρv, are also given. These results are also transformed so as to give P/kT, lnz, and v as power series in λ with the coefficients functions of ρ.
A development for P/kT for an arbitrary lattice with different interactions for different distances between lattice sites is also given. The equation permits numerical evaluation without too great difficulty.
Spectroscopic Studies of Rotational Isomerism in Fluorinated Ethanes. III. CF2Cl–CF2Cl and CF2Br–CF2Cl
Authors: Kagarise R. E. 
Published: January 2005

The phenomenon of rotational isomerism has been studied in CF2Cl–CF2Cl and CF2Br–CF2Cl by observing the temperature and state dependence of their infrared absorption spectra in the 2–18 μ region. In CF2Cl–CF2Cl, the trans-isomer persists in the crystalline solid, and is also the more stable form in the liquid and vapor states. The energy difference between the trans (C2h) and gauche (C2) forms in the vapor was observed to be 500±200 calories/mole.
In CF2Br–CF2Cl, the selection rules for the two probable isomeric species (Cs and C1) are not sufficiently different to facilitate a direct determination of the symmetry of the form which persists in the solid state. However, a comparison of the infrared spectrum of CF2Br–CF2Cl with those of CF2Cl–CF2Cl and CF2Br–CF2Br indicates that the persistent isomer is the pseudo-trans-form (Cs symmetry). This trans-form is also the more stable isomer in both the liquid and vapor phases, the energy difference being 520±200 and 600±200 calories/mole, respectively.
New Approach to the Quantum-Mechanical Analysis of the Electronic Structures of Molecules. The Method of Deformed Atoms in Molecules
Authors: Arai Tadashi 
Published: January 2005

A modification of Moffit's method of atoms in molecules is here proposed. In this treatment, the modified atomic functions X are introduced, which are made up from the exact eigenfunctions of atoms modified by correction factors so as to take account of the deformation of atoms in molecules. The advantage of these basic functions X is as follows. Firstly, the difficulty caused by the correlation energy in atoms can be removed by the use of the experimental atomic term values just as in Moffitt's method. Secondly, the common effective charges for neutral and ionic structures can be applied for the convenience of calculating the interaction operators, which sometimes produces serious errors in Moffitt's method. Moreover the improvement on the original Heitler-London treatment—corresponding to Wang's or Weinbaum's work for the hydrogen molecule—can be expected. Then, it is discussed how to determine these modified atomic functions in order that the results appertain to the good range in spite of the rather simple calculation.
The energy loss of atoms in molecules, induced by the deformation, is corrected, and the interatomic interaction energy is calculated by the use of the approximate functions composed of the orbital functions, where the molecular orbital method can be utilized for saving the difficulty of the higher order permutations. Then the unsatisfactory results, obtained in the calculation of Li2 by utilizing the common effective charges in Moffitt's method, are improved.
Experimental Determinations of Charge Transfer Cross Sections and Secondary Electron Emission by Ion Bombardment
Authors: Ghosh S. N. , Sheridan W. F. 
Published: January 2005

The method utilized by the authors for determining charge transfer cross sections has been improved and applied to symmetric and unsymmetric reactions involving the inert gases, N2, H2, CH4, C2H4, C2H6, and C3H8. The cross sections were found to be about 20% higher than the values previously reported. The discrepancy can be explained by the fact that in previous experiments cross sections were determined from net charge measurements without taking full account of the secondary electrons impinging on the plate where the charge transfer ions were collected.
As expected from adiabatic hypothesis, the reactions involving mixtures of gases having nearly equal ionization potentials were found to have maximum cross sections for low-energy ions. The interaction distances were calculated from the observed ion energy for which the cross sections are a maximum.
The method described here can be utilized to determine the secondary electron emission from a metal surface due to ion bombardment. Such determination has been made for a brass surface. Relating the variation of emission with the ion mass and energy, it is found that the emission varies inversely as the square root of the ion mass.