bluuebunny/crossref_metadata_2025_split huggingface dataset:
One-Center Basis Set SCF MO's. I. HF, CH4, and SiH4
Authors: Moccia Roberto 
Published: January 2005

One-center SCF MO ground-state wavefunctions are reported for HF, CH4, and SiH4. The molecular orbitals are expressed in terms of Slater-like functions all centered at a common origin. The basis sets employed contain more than 25 functions including, for the spherical harmonics, values of l up to 3. The results of the calculations here reported, performed by the use of a large electronic computer, refer to the geometrical configurations which, among many others considered, gave the minimum of the total energy.
The equilibrium bond length thus determined for HF is 1.728 a.u. with a corresponding value of the energy of — 100.0053 a.u. and of the electric dipole moment of 2.104 D. For CH4 and SiH4 the equilibrium configurations were found to possess tetrahedral symmetry with bond lengths of 2.08 and 2.787 a.u. and energies of — 39.86597 and — 290.1024 a.u., respectively.
The general features and capabilities of the one-center expansion approach to molecular systems are discussed.
Raman Spectral Studies of Oleums
Authors: Walrafen George E. 
Published: January 2005

Relative integrated Raman intensities of oleums reported earlier [G. E. Walrafen and T. F. Young, Trans. Faraday Soc. 56, 1419 (1960)] have been redetermined, and the measurements have been extended to other Raman bands. The new intensity data indicate low degrees of dissociation of H2S2O7, and they constitute evidence for the presence of small amounts of H2O3O10.
When X(SO3), the stoichiometric mole fraction of a mixture of sulfur trioxide and sulfuric acid, is increased from zero to 0.3, relative integrated intensities of Raman bands of H2SO4 and of H2S2O7 are observed to decrease or to increase, respectively, in nearly perfect agreement with corresponding variations of Σ[H2SO4] and Σ[H2S2O7], the stoichiometric sulfuric or disulfuric acid molarities. These agreements indicate that [HS2O7—] is small, and they provide an explanation for the observed low electrical conductivities. When X(SO3) is increased above 0.3, however, SO3 and H2S3O10 appear and increase in concentration, while [H2S2O7] attains a maximum value of 9.8 mole·liter—1 at X(SO3)≈0.5, and [H2SO4] approaches zero at X(SO3)=0.6. Above X(SO3)=0.6, S3O9 makes its appearance and increases in concentration as [H2S3O10] attains a maximum value of ∼1.4 mole liter—1 at X(SO3)≈0.74. [SO3] and [S3O9] continue to increase until X(SO3)=1.0, at which composition [SO3]≈17.4 mole·liter—1 and [S3O9]≈2.1 mole·liter—1.
Vibrational frequencies of S2O72—, HS2O7—, and H2S2O7 obtained from studies of molten K2S2O7 and (NO2++HS2O7—), and from studies of oleums, have been compared, and the vibrations have been assigned and correlated with the aid of polarization data. The intensity data obtained from studies of molten (NO2++HS2O7—) provide additional evidence that HS2O7— concentrations are generally low in oleum solutions. Vibrations of SO3, H2S3O10, and S3O9 are also considered briefly.
Electron Spin Resonance of Ultraviolet-Irradiated Compounds. II. Peroxide-Initiated Radicals in Straight Chain Alkenes
Authors: Beasley Edward E. , Anderson Roy S. 
Published: January 2005

Selected low molecular weight hydrocarbon glasses at approximately 77°K were irradiated with ultraviolet light, producing trapped radicals which were studied by ESR. Straight chain alkenes exhibited spectra which were demonstrated, through tests with 1-hexene, to be the result of free radical reactions initiated by the photolysis of peroxide impurities. Other experiments with 1-hexene are reported.
Symmetric alkene spectra were interpreted in terms of the following model: (A) Primary (peroxide) radicals, formed by uv photolysis, react with molecular end groups by abstraction or terminal addition to produce the observed spectra. (B) In the π-electron radicals assumed to be formed, the isotropic proton hyperfine coupling constants (which determine the observed approximate component separations) are taken to have the fixed values: α protons, 22 G; methylene protons, 22 G (β1) and 44 G (β2); methyl protons, 22 G. (The α-proton anisotropic splitting is manifested only as a broadening of the components.) In terms of this model, interpretations of the spectra obtained from 2-pentene, 1- and 2-hexene, 1-, 2-, and 3-heptene, 1- and 2-octene, and 1-decene are presented.
Electronic Distribution in Some Conjugated Ketones. Molecular Orbital Calculations Including Overlap
Authors: Payette Gisele , Sandorfy C. 
Published: January 2005

Electronic charge distributions in 8 conjugated ketones were computed by the semiempirical molecular orbital method in Wheland's approximation, including overlap between adjacent atoms. It is found that inclusion of overlap leads to a clearer picture of charge distribution. It is shown that covalent and ionic contributions to bond energies may decrease or increase at the same time upon excitation, or a structural change in the π system.
A new ``Coulombic bond order'' is defined, giving a measure of bond energies in terms of Coulombic interactions between local charges.
Limitations of the Reflected Shock Technique for Studying Fast Chemical Reactions and Its Application to the Observation of Relaxation in Nitrogen and Oxygen
Authors: Strehlow Roger A. , Cohen Arthur 
Published: January 2005

Strip film and multiple spark schlieren pictures of reflected shocks were taken in the gases He, A, N2, O2, H2, NO, CO2, N2O, CH4, and C3H8. Interaction of the reflected shock with the boundary layer behind the incident shock was observed in all gases except He and A. The bifurcation and acceleration associated with the interaction limits the use of the reflected shock region for high-temperature kinetic and equilibrium studies. It was possible to minimize the effects of this interaction by using gases with high γ and confining measurements to a region near the back wall. Reflected shock observations agreed with Mark's theory of the development of bifurcation but disagreed with his predicted deceleration of the reflected shock.
From comparison of incident and reflected shock velocities, measured at the backwall, with ideal one-dimensional theory, it was concluded that calculations of the temperature behind the reflected shock from incident shock velocities would yield high results.
Decelerations of the reflected shock in N2 and O2 have been observed in the strip films and were related to the vibrational relaxation behind the reflected shock. Measurements of relaxation times from the film yielded values which are in good agreement with Blackman's data. These experiments indicate that changes in reflected shock velocity can be used to observe the overall reaction rates of fast chemical reactions.
Generalization of the One-Dimensional Ising Model Applicable to Helix Transitions in Nucleic Acids and Proteins
Authors: Hill Terrell L. 
Published: January 2005

The exact treatment of the Ising model for an infinite, one-dimensional system has been generalized to make it applicable to the helix transition in synthetic polynucleotides, DNA, synthetic polypeptides, and proteins. The particular advantages of the present treatment are flexibility and generality: the free energies of sequences of similar units of any size can be assigned arbitrary values in the final equations; also ``mismatching'' between the two strands in a double helix is allowed for.
Anderson's general theory of collision line broadening has been applied to H2O–N2 encounters. The only attractive force was assumed to be that between the H2O dipole, μ=1.87×10—18 esu, and the N2 quadrupole, qN2, an adjustable parameter. A second adjustable parameter, bm, the distance of closest approach, includes the effects of all other forces. The IBM 704 was used in the calculation. Effects of varying the parameters were noted for a number of lines, and in the final calculation, which yielded the widths of all significant type B transitions up to J″=13, parameters qN2=2.62×10—26 esu and bm=3.2 A which give an exact fit of the observed width of the microwave line 6—5—5—1, were adopted. The temperature dependence of the line width over the range 220–2400°K, and the effects of vibration-rotation interactions were also calculated. At 300°K widths vary from 0.11115 cm—1 atmos for 11—1—1 to 0.03200 cm—1 atoms—1 for 14—13—13—13, there being a general decrease in width with increasing J, and at a given J, decreasing width with increasing τ.
Theoretical Pre-Exponential Rate Factors for Abstraction Reactions
Authors: Sinanoglu Oktay , Pitzer Kenneth S. 
Published: January 2005

Equations have been derived for the pre-exponential rate factors of abstraction reactions. The activated complex is considered as made up of three rigid groups. Classical partition functions are used and it is shown that the use of classical methods gives a simple expression which requires only a knowledge of several force-constants and bond lengths; thus the need for detailed structural information on reactants and complex and for calculations of moments of inertia and vibrational frequencies is eliminated. It is shown that quantum corrections need not be considered in many cases, although if desired, they may be estimated from a graph provided.
The method is applied to four hydrogen abstraction reactions and to the reaction, CCl3Br+Br=CCl3+Br2. Satisfactory agreement is obtained.
Interaction of Rare Gases with Metal Surfaces. I. A, Kr, and Xe on Tungsten
Authors: Ehrlich Gert , Hudda F. G. 
Published: January 2005

The interactions of argon, krypton, and xenon with a tungsten surface have been examined in the field emission microscope. Bombardment by rare gas ions results in a penetration of the lattice and an apparent diminution of the work function; bombardment damage is partly annealed between 79° and 300°K. Adsorption lowers the work function by 1.38 ev for Xe, on saturation at 79°K, 1.18 ev for Kr at 20°K, and 0.87 ev for A at the same temperature. The work function diminishes monotonically with Xe coverage even after more than a single layer is formed.
Binding to the surface is structure sensitive—it is strongest around the 100 pole, in the vicinity of the 116 and 130 planes, and weakest at the 111. This sequence of binding energies corresponds to that calculated for different lattice sites on the assumption of dispersion forces. The lowering of the work function caused by adsorption is interpreted as a polarization of the gas atoms by the dipole layer of the metal surface; formally, the interactions at a metal resemble those of the rare gases adsorbed on ionic crystals. Interaction of polarized adatoms and the anti-parallel field applied for electron emission increases the free energy of the adlayer, bringing about rearrangements particularly important for adsorbed argon.
Observations of changes in emission with temperature yield a heat of desorption of 8 kcal/mole for Xe, as well as the following values for the activation energy for surface diffusion: Xe over the (310), toward the (100), ED=3.8 kcal/mole, over the (111), 1.5*lt;ED&lt;3.4 kcal/mole; for the diffusion of Kr and A over the (310) toward the (100), ED&gt;1.1 kcal/mole and ED&lt;0.9 kcal/mole, respectively.
Kinetics of the Thermal Decomposition of Dimethylmercury. I. Cyclopentane Inhibition
Authors: Russell Morley E. , Bernstein Richard B. 
Published: January 2005

The kinetics of the pyrolysis of gaseous dimethylmercury have been studied in the presence and absence of cyclopentane inhibitor from 290–375°C for the inhibited and 265–350°C for the uninhibited reactions. The decomposition in excess cyclopentane is first order, with methane the major product (accounting for &gt;95% of the carbon). Rate constants are dependent upon the ratio of dimethylmercury (DMM) to cyclopentane and upon total pressure. The constant for DMM loss is: kD=1.1×1015 exp(—55 900/RT) sec—1. The rate constant (from combined data on DMM loss and CH4 formation) extrapolated to the fully inhibited, high-pressure limit is: k1=5.0×1015 exp(—57 900/RT) sec—1.
The data for the uninhibited decomposition agree with the literature; a partial mechanism is suggested which predicts the transition from chain to nonchain behavior with increasing temperature.
For the inhibited reaction the following mechanism is proposed: (1) Hg(CH3)2→HgCH3+CH3, (2) HgCH3→Hg+CH3, (3) CH3+Hg(CH3)2→CH4+CH3HgCH2, (4) CH3+C5H10→CH4+C5H9, (5) CH3+Hg(CH3)2→C2H6+HgCH3, (6) 2 CH3→C2H6, (7) CH3HgCH2→HgCH3+CH2.
Using the present value of E1=57.9±1.4 kcal/mole in conjunction with known thermochemical data, E2=0±3 kcal/mole. From the inhibition data, k3/k4=0.7±0.2 at 300°C, with a very small temperature coefficient. The inert gas pressure effect is evidence for the unimolecular nature of step (1).
Molecular Configurations of Vinyl Polymers with Strictly Regular Structures and Their Mean Dimensions and Electric Moments in Dilute Solutions
Authors: Nagai Kazuo 
Published: January 2005

Neglecting the long-range interaction between segments, general expressions for the mean dimensions and the electric moments of isotactic and syndyotactic vinyl polymers in dilute solutions are derived. For the comparison with experimental results, the following expression is employed for the potential energy of the hindered rotation around C–C links of a skeletal chain: E=(E0/2)[1−cos(θ−θ0)],where θ is a twisted angle from the trans position with θ0 as the most probable one, and E0 is the maximum height of the potential energy. For simplicity numerical calculations of the electric moments are restricted to vinyl polymers in which the direction of the electric moment vector of each substituted group coincides with one of four symmetry axes of tetrahedral model of carbon atom.
For isotactic polymers three cases are examined. The first: all C–C links are twisted in the same manner. The second: consecutive two C–C links are twisted to inverse directions to each other. The third: potential energies of the hindered rotation around C–C links have their minima at the same angles as in crystalline state. From consideration of the minimum distance between two adjacent substituted groups, it is concluded that, if the molecular dimension of isotactic polystyrene is not far apart from that of atactic polystyrene, the deformation of the second type would be less probable. When taken into account the collisions between different parts of the polymer molecule, the deformation of the third type or the other similar to it may be most probable. In this case when 〈R2〉/nb2 is taken to be 12∼13, then 〈u2〉/Nu02 should become 1.5∼1.7, N=n/2 being degree of polymerization. For syndyotactic polymers, two unknown parameters involved in the theory may be uniquely determined by measuring 〈R2〉/nb2 and 〈u2〉/Nu02.
Diffusion and Viscosity in a Spherical Cavity
Authors: Broersma S. 
Published: January 2005

A system consisting of two, in principle concentric, spherical surfaces separated by a fluid, is considered. The torque and force required to rotate and translate the inner sphere is calculated, as well as the work necessary to maintain fluid flow around it, the flow pattern at the outer sphere being specified. Using this, general expressions for the diffusion constants for rotation and translation for the inner sphere and for the effective viscosity of the bulk liquid are obtained. The inner sphere (a) can be viscous, its surface may slip or adsorb fluid. The effect of a perturbation in the flow pattern at the outer surface (R) is examined. For a small value of a/R, the expressions become those given by Stokes and Einstein for dilute solutions.
For the ratio a/R≈1, the expressions apply to liquids flowing through membranes or porous media. Rotational diffusion of paramagnetic hydrates in diamagnetic environment, translational diffusion of ions through membranes, the viscosity of concentrated suspensions and fluid flow through porous media are discussed.
Temperature Dependence of Proton Relaxation Times in Aqueous Solutions of Paramagnetic Ions
Authors: Bernheim Robert A. , Brown Thomas H. , Gutowsky H. S. , Woessner D. E. 
Published: January 2005

The nuclear magnetic relaxation times of protons in aqueous solutions of paramagnetic ions have been measured as a function of temperature. For Mn++ ions, the proton T1 and T2 were measured at 10, 20, and 28 Mc/sec, and for Co++, Cu++, and Gd+++ ions, 20 Mc/sec. The temperature effects observed can be explained by incorporating the proper temperature dependences of the several correlation times into the general Bloembergen-Solomon relaxation expressions.
In the case of Mn++ solutions, which have a T1/T2 ratio of about 5.5 at room temperature and 20 Mc/sec, chemical as well as electron exchange and dipolar interactions are found to be important. Analysis of the data by means of the equations developed provides information concerning the chemical exchange of solvent protons with those in the hydrated Mn++ ion. An activation energy of 8.4 kcal/mole and other parameters for this process are evaluated.
The temperature dependence of T1 and T2 in the Co++, Cu++, and Gd+++ solutions can be explained by the temperature dependence of the dipolar interaction alone. Varying the anion in Cu++ solutions had little effect on T1 or its temperature dependence; also, T1 for Cu++ solutions was found to vary inversely with concentration over the whole temperature range studied.
Vibrational Spectra of Primary and Secondary Aliphatic Amines
Authors: Stewart James E. 
Published: January 2005

The infrared absorption spectra of twenty primary and thirteen secondary amines have been studied. A strong band, assigned to the asymmetric C–N stretching mode of secondary amines, is found at 1139±7 cm—1 in compounds having a primary alpha carbon and at 1181±10 cm—1 in compounds having a secondary alpha carbon. The primary amines have a corresponding C–N band at 1079±11, 1040±3, and 1030±8 cm—1 for compounds with primary, secondary, and tertiary alpha carbons, respectively. A strong broad band is found at 739±11 and 718±18 cm—1 in the spectra of secondary amines having primary and secondary alpha carbons. This absorption is assigned to the N–H bending mode. In liquid primary amines, pairs of strong bands at 778±15 and 825±15, 794±16 and 840±11, and 776±8 and 833±18 cm—1 are assigned to the symmetric and asymmetric NH2 bending modes in compounds having primary, secondary and tertiary alpha carbon atoms, respectively. Shifts in frequency of some of these bands are noted in the gas phase or in solution. A very strong, broad band centered at less than 290 cm—1 is observed in the spectra of the primary amines, but not the secondary amines. This band disappears in the gas phase and is assigned to the torsional oscillation of the —NH2 group.
A simplified normal coordinate treatment of the R—NH2 and R2—NH vibrations is given in support of the assignments.
LCAO-MO SCF Study of B2
Authors: Padgett Alice A. , Griffing Virginia 
Published: January 2005

An LCAO molecular orbital study of B2 was made for three distances of the internuclear parameter. SCF molecular orbitals were obtained for the 3Σg— state, which is the reported ground state of the molecule. Total molecular energies of other low-lying states were calculated using the 3Σg— SCF molecular orbitals. These results indicate that the 5Σu— state is the ground state of B2; however, the 3Σg— and 3Πu states lie only about 1.5 ev above the 5Σu— state and may become lower in a more refined calculation.
A Mulliken electronic population analysis was applied to B2. For comparative purposes a summary of overlap and atomic populations of Li2, C2, N2, and O2 is included.
Microwave Spectrum, Barrier to Internal Rotation, and Structure of Methyl Formate
Authors: Curl R. F. 
Published: January 2005

Rotational constants have been assigned to the following isotopic species of methyl formate by investigation of their microwave spectra: HCOOCH3, DCOOCH3, HCOOCH2D, HCOOCD3, HC13OOCH3, HCOOC13H3, HCO18OCH3, and HCOO18CH3. The following structural parameters were obtained from these rotational constants: r (C=O) = 1.200±0.01 A, r (C–O carboxyl) = 1.334±0.01 A, r (C–O methoxyl) = 1.437±0.01 A, r (C–H carboxyl) = 1.101±0.01 A, r (C–H methyl) = 1.086±0.015 A, ∠O=C–O=125°52′±1°, ∠H–C–O (carboxyl) = 109°18′±1°, ∠C–O–C = 114°47′±1°, and ∠H–C–H = 110°40′±1.5°. The carbon-oxygen skeleton is planar with the methyl group cis to the carboxyl oxygen. The methyl group axis has been assumed to be along the C–O (methoxyl) bond, although some evidence suggests that it may be tilted.
The barrier to internal rotation of the methyl group was calculated from the splittings observed in the rotational transitions of the ground torsional state for several isotopic species and found to be 1190±40 cal/mole.
The dipole moment was calculated from the observed Stark effect and found to be 1.77±0.03D. The dipole moment lies at an angle of 39.4±2° from the C=O bond and roughly on the line between the ester oxygen and the carboxyl oxygen.
NMR Study in Rochelle Salt
Authors: Blinc R. , Prelesnik A. 
Published: January 2005

The angular dependence of the proton magnetic resonance absorption of a Rochelle salt single crystal has been measured. The experimental second moments are compared with the theoretical curves, as calculated for the structures proposed so far. Lösche's model was found to reproduce the qualitative form of the angular dependence, whereas the other structures gave no agreement at all.
The occurrence of transitions in the proton magnetic absorption line widths at +24°C and below —20°C demonstrates that the assumption of protonic motion, upon which the dynamic theories of ferroelectricity in Rochelle salt are based, is essentially correct.
Some Effects of Vapors on Electret Behavior
Authors: Beeler J. R. , Stranathan J. D. , Wiseman G. G. 
Published: January 2005

The effects of various vapors on the growth and decay of electret polarization have been studied. Particular emphasis was given to the effect of water vapor on polyvinyl acetate. The observed effects appear to arise from two causes: (1) a decrease in the relaxation time and an increase in the magnitude of the volume polarization following infusion of vapor into the dielectric; (2) an increase in the transfer of charge by means of interfacial discharge at the dielectric-electrode gap. The infusion of a polar vapor into a nonpolar solid dielectric gave anomalously large values of volume polarization.
The dielectrics studied were polyvinyl acetate, polyethylene, two acrylic resins, and carnauba wax. The vapors used successfully were water and chlorobenzene; unsuccessful attempts were made to use benzene and isopropyl ether.
Ultraviolet Resonance Spectrum of the Iodine Molecule
Authors: Verma R. D. 
Published: January 2005

The ultraviolet resonance spectrum of I2 observed in electric discharges in the region 1830–2370 A has been photographed at high resolution with a 21-ft vacuum grating spectrograph, and a thorough and complete analysis of the data in this region is given. The five doublet resonance series are shown to be excited from five rotational levels of vibrational level v″=0 of the ground state of I2 to three vibrational levels (vn′,vn+0′,vn+4′) of an upper electronic state by a single iodine atomic line 1830.4 A. The rotational constants for the ground state of I2 may be represented: (1)v=0.03734−0.0001208 (v+12)+0.444×10−6(v+12)2−1.839×10−8(v+12)3−0.057×10−10(v+12)4(2)v=1.99×10−9+1.236×10−10(v+12).The ground-state ΔG(v+12) values have been obtained from v″=0 up to the dissociation limit. A precise value of the dissociation energy of I2, has been found to be 12 452.5±1.5 cm—1 as against the previous value of 12439±8 cm—1.
The potential energy curve of X 1Σg+ has been computed by using the Rydberg-Klein-Rees method after modifying its final expressions, right up to the dissociation limit, and certain curious features in the neighbourhood of the dissociation limit are pointed out. The curve follows the van der Waals force law c/r6 between r=4.6 A and r=6.4 A with c=3.7×106. Various possibilities for the nature of the upper electronic state are discussed.