bluuebunny/crossref_metadata_2025 huggingface dataset:
Thermodynamics of Vaporization of Lithium Oxide, Boric Oxide, and Lithium Metaborate
Authors: Hildenbrand D. L. , Hall W. F. , Potter N. D.
Published: January 2005

The vapor pressures of lithium oxide, boric oxide, and lithium metaborate have been measured by the torsion—effusion method. For lithium oxide, the magnitude of the observed pressure indicates vaporization largely to lithium oxide molecules. The boric oxide measurements yield an entropy for B2O3(g) that is consistent with calculated entropies based on recent matrix-isolation spectral data, and, therefore, support the assigned molecular constants. Lithium metaborate, the one-to-one mixture of the two oxides, vaporizes congruently to mixed-oxide molecules. Third-law treatment of the vapor pressure data gives heats of sublimation at 298°K of 103.6±3, 103.1±2, and 86.3±3 kcal/mole for Li2O(g), B2O3(g), and LiBO2(g), respectively. When combined with data for the condensed phases, the results yield ΔH298=—75 kcal for the reaction Li2O(g)+B2O3(g)=2LiBO2(g).
Frequency Distribution and the Specific Heat of NaCl
Authors: Arase Elizabeth M. , Hatcher Robert D. , Neuberger Jacob
Published: January 2005

Using the Kellermann model of the NaCl crystal, the eigenfrequencies of NaCl have been found for a sub-division of 12, 16, 18, 24, 36, and 48 of the wave vector along each axis of the reciprocal cell. From these frequencies the frequency distribution has been found, using the usual sampling technique. A comparison of these distribution functions is given. Assuming the results of the 48 division to be correct, the percentage errors of the other distribution functions based on fewer frequencies have been found as a function of the number of frequencies per frequency interval. From these results, the accuracy of the 48-division calculation has been estimated. The calculated heat capacity at constant volume changes by about 3% at 10°K due to the various frequency distributions, but above 20°K the values agree within four significant figures.
Pure Nuclear Quadrupole Resonances of Several Chlorinated Cyclopropanes
Authors: Todd J. E. , Whitehead M. A. , Weber K. E.
Published: January 2005

The nuclear quadrupole resonances of five chlorinated cyclopropanes are given, and the chlorine frequencies are correlated with the effective orbital electronegativity of the carbon to which the chlorine is bonded. The concept of molecular inequivalence of the chlorine atoms is introduced in the interpretation of the temperature dependence of the frequencies in 2, 2, 2′, 2′-tetrachlorobicyclopropyl.
Vapor-Phase Equilibrium of NO, NO2, H2O, and HNO2
Authors: Waldorf D. M. , Babb A. L.
Published: January 2005

The thermodynamic equilibrium constant for the vapor-phase reaction NO+NO2+H2O⇌2HNO2 has been determined at reduced pressures by evaluating the equilibrium distribution of known quantities of the reactant gases by measurements of light absorption by nitrogen dioxide. The value of the equilibrium constant at 25°C is K1=2.38 atm—1, which corresponds to ΔF°=—0.512 kcal/mole. The free energy of formation of HNO2 vapor at 25°C and at isomeric equilibrium is ΔFf°=—11.019 kcal/mole, based on the equilibrium measurements and the free energies of formation of NO, NO2, and H2O.
Interactions in Polar Media. II. Continua
Authors: Marcus R. A.
Published: January 2005

It is shown that the electronically polarizable continuum model of a particle satisfies the equations of part I, after suitable choice of operator Ai appearing there. The proof is given for the case where the system is regarded as composed of particles and treated statistically mechanically. It is also given for the case where several particles receive special attention and the remainder of the system (the ``medium'') is treated as an orientationally and electronically polarizable continuum. For the second case it was necessary to extend the results of Part I, so as to include several particles in the presence of the above ``medium'' and to compute the free energy of such systems. Calculations are given for media possessing equilibrium and nonequilibrium dielectric polarization.

It follows from the foregoing proofs that a wide variety of models assumed in the literature for treating polar interactions are special cases of the model in Part I and of the extension to particle-medium systems in this paper. Electrode systems, for example, are included, even when the electrode is treated in the usual dielectric continuum manner.

The relation and relative merits of the two models for the induced charge distribution that are standard in the literature, both special cases of Part I, are discussed. These models are the induced dipole and the electronically polarizable continuum. Possible direct experimental investigation of the second of these by scattering experiments is examined.
Ion—Molecule Reactions Leading to NO+ Formation
Authors: Galli A. , Giardini-Guidoni A. , Volpi G. G.
Published: January 2005

Possible ion—molecule reactions leading to NO+ formation have been investigated. It has been found that O++N2→NO++N,k1≈2.2×10−11 cm3 sec−1,N2++O2→NO++NO,k2≤2.1×10−13cm3sec−1,O2++N2→NO++NO,k5≤2.1×10−13cm3sec−1.Evidence has also been found for the following reaction of N+ ions N++O2→NO++O,k6≈1×10−10cm3sec−1,N++CO2→NO++CO,k7≈3×10−11cm3sec−1.
Photochemical Formation of Phenanthrene from cis-Stilbene in the Vapor Phase
Authors: Srinivasan R. , Powers John C.
Published: January 2005

Photolysis of cis-stilbene in the vapor phase at 170° leads to the formation of trans-stilbene, phenanthrene, and hydrogen. The formation of phenanthrene is not eliminated by the addition of oxygen (35 mm) or nitric oxide (6 mm), nor is the rate affected by large excesses of ether or cyclohexane. It is believed that phenanthrene and hydrogen are formed from cis-stilbene by an intramolecular process which probably proceeds in a single step—the elimination of hydrogen occurring at the same time as the closure of the third ring. The reaction is also observed to occur in the pyrolysis of cis-stilbene at 550°. Qualitative results on the photolysis and pyrolysis of 1,4-diphenyl-1,3-butadiene in the vapor phase are reported. Quantum yields for the formation of phenanthrene in the photolysis of cis-stilbene in cyclohexane solution have been obtained. An earlier report that phenanthrene is a product in solution only in the presence of oxygen has been confirmed. The dissimilarities between the mechanisms of the formation of phenanthrene in the vapor phase and in solution are discussed.
Analysis of the Electron Spin Resonance Spectra of Aromatic Nitrosubstituted Anion Radicals
Authors: Rieger Philip H. , Fraenkel George K.
Published: January 2005

Molecular orbital calculations using the Hückel LCAO theory and the approximate configuration interaction treatment suggested by McLachlan have been performed on a large series of nitrosubstituted aromatic anion radicals. By properly adjusting the Coulomb and resonance integrals for the nitro group, a good quantitative correlation is obtained between the calculated spin densities and the experimental proton hyperfine splittings for most of the compounds studied. Procedures are developed to account for the variations in hyperfine splittings with different solvents, and an equation is formulated which gives excellent predictions of the splitting from N14 nuclei in the nitro groups. In addition, the calculations provide a basis for the qualitative discussion of the effects of sterically hindered nitro groups on the hyperfine splittings, and of the apparently anomalous spin densities and linewidth variations in some of the meta-dinitrobenzene anions. Polarographic half-wave potentials are also correlated with the calculated pi-electron energies. Experimental data are given for the ESR spectra of several substituted nitrobenzene anions not previously reported.
Excitation of π Electrons in Polystyrene and Similar Polymers by 20-keV Electrons
Authors: Swanson N. , Powell C. J.
Published: January 2005

Excitation of the π electrons in thin films of polystyrene and some similar polymers has been observed in the characteristic energy loss spectra of 20-keV electrons scattered at zero angle. The observed energy loss of approximately 7 eV corresponds to the strong uv absorption near 1800 Å in benzene and its derivatives. An energy loss of 6.97±0.10 eV was measured in films of atactic and isotactic polystyrene, styrene ethylene copolymer, and poly 2,3,4,5,6-pentadeuterostyrene, and an energy loss of 7.25±0.15 eV was measured in poly 2,3,4,5,6-pentafluorostyrene. These energy losses appeared as sharp peaks superimposed on a very broad and more intense loss peak with a maximum at 21.3±0.3 eV in all the electron energy loss spectra obtained. The results for the energy loss attributed to the π electrons are correlated with relevant uv absorption data. A discernible decrease in the measured ∼7-eV loss occurred during electron bombardment of the specimens, and is attributed to film contamination and breakdown. The angular distribution of the intensity of each loss in isotactic polystyrene about zero scattering angle was also measured.
External Heavy-Atom Spin—Orbital Coupling Effect. IV. Intersystem Crossing
Authors: McGlynn S. P. , Daigre J. , Smith F. J.
Published: January 2005

The relative phosphorescence to fluorescence quantum yields and phosphorescence lifetimes of naphthalene have been measured in a number of glassy media, some of which contain perturbing atoms of large atomic number. The intersystem crossing process S′→T is very sensitive to external heavy-atom perturbation. It is shown that the order of decreasing sensitivity to this perturbation is: intersystem crossing process (S′→T)>phosphorescence quenching process (T→S)>phosphorescence emission process (T→S). It is strongly suggested by the data contained herein that heavy atom quenching of fluorescence can indeed be attributed primarily, if not entirely, to increase in the probability of the intersystem crossing process. A number of possible uses for the heavy-atom technique are suggested.
Some Analytic Solutions of the Hartree—Fock Equations by an Iterative Least-Squares Method
Authors: Merts A. L. , Torrey M. D.
Published: January 2005

Approximate ground-state solutions of the Hartree—Fock equations are given in analytic form for all atoms having 3≤Z≤13, and the ions of Mg+, Na+, Al+. The solutions are obtained by an iterative least-squares procedure for determining the optimum nonlinear parameters occurring in the trial wavefunctions. The accuracy is equal to or better than that obtained by standard numerical methods.
NMR in Hydrate Crystals: Structural Information from Second Moments
Authors: Pedersen Bjo/rn
Published: January 2005

The effects of fast 180° flip motion of the water molecules in hydrate crystals on the first and second moment of the proton magnetic resonance spectrum are explored theoretically. When the spectrum consists of two well-separated line components, it is proved that the first moment of the spectrum about the midpoint is the correct measure of the interaction responsible for the main splitting. Earlier this has been proved for a system of water molecules rigidly bound in the lattice.

A formula for the second moment, consisting of an intramolecular term, an intermolecular term, and a term due to unlike spins, is derived. The first and the last of these terms are shown to be independent of the shape of the spectrum. The intermolecular term, however, is proportional to a factor which is 5/6 when the spectrum consists of two well-separated line components and 1 when the spectrum shows no sign of a fine structure. This shape dependence of the intermolecular term is due to the fact that some of the intermolecular spin exchange transitions are forbidden to first order when the spectrum consists of two well-split lines. It is pointed out that the partial quenching of some transitions when the spectrum shows signs of a fine structure will in general lead to an uncertainty in the theoretical second moment. It is concluded that to get accurate structural information from second moments, the fine structure has to be completely resolved or the spectrum should show no signs of a fine structure.

The obtained formula for the second moment has been used to calculate the second moments for a particular set of orientations of a single crystal of gypsum. The experimentally measured second moments show fair agreement with the calculated values.
Reaction Kinetics of a Long Chain Molecule
Authors: Lazare Leon
Published: January 2005

A derivation based on combinatorial analysis is presented for the equations of the kinetics of reactions of sites on a long chain molecule, wherein the first-order kinetics depend on the states of the nearest neighbors. The derivation results in a set of differential equations practically identical to those recently developed by J. B. Keller; however, a more fundamental hypothesis has replaced Keller's hypothesis concerning the distribution of reacted sites. The analysis admits a greater choice of initial conditions, and also yields directly the distribution of sequences of k unreacted sites.
Polarization Effects in the Ionic Conductivity of Alkali Halide Crystals. I. AC Capacity
Authors: Jacobs P. W. M. , Maycock J. N.
Published: January 2005

The three principal theories which have been advanced to explain ac polarization effects in ionic conductors are examined and the approximations inherent in them are discussed. Explicit formulas for the polarization capacity are extracted and used to predict the values of the frequency-dependent component of the capacity of potassium chloride crystals between platinum electrodes. The experimental results for pure KCl are in good agreement with these predictions, but for KCl crystals doped with SrCl2, the agreement is less satisfactory. It is concluded that the polarization observed at high temperatures is due to the blocking of the charge carriers at the electrodes and that the linearized theory gives, in general, a good account of this effect.
Intramolecular Electron Transfer in Bis(p-Nitrophenyl) Anions and Its Effect on Electron Spin Resonance Hyperfine Structure
Authors: Harriman John E. , Maki August H.
Published: January 2005

The hyperfine structure of electrochemically generated mononegative ion radicals of the type[Complex chemical formula]has been observed, where X=CH2, S, O, CH2CH2, and where X is absent. The hyperfine structure is found to be especially sensitive to the intramolecular electron transfer rate when the latter is the same order of magnitude as the hyperfine intervals when expressed as frequencies. The transfer rate is found to be sensitive to the solvent, and a model is presented that expresses the trapping of the electronic charge by the orientation of solvent dipoles. The mechanism for electron transfer then proceeds through the random motions of the solvent molecules.

Hyperfine structures are calculated for a series of transfer rates on the basis of the Anderson—Weiss model for motional narrowing. Good agreement is found between the unusual hyperfine structure observed experimetally and the calculated spectra for certain values of the transfer rate.

The shape of the composite two-electron polarographic reduction wave is related to the equilibrium constant for the reaction, S+S==2S—, assuming reversibility of all electron-transfer reactions at the electrodes. Equilibrium constants are reported.
Ultraviolet Spectra of the Nitrogen Pink Afterglow
Authors: Fairchild C. E. , Prag A. B. , Clark K. C.
Published: January 2005

Ultraviolet spectra from 4200 to 1150 Å of the recurrent, brilliant afterglow in fast-flowing pure nitrogen are obtained using a vacuum spectrometer at 0.5-Å resolution with photographic and photoelectric detection. Molecular emission features generally resemble those of a direct discharge. Atomic lines from the 10.7-eV 3s 2P level are present, but there are none from the 10.4-eV 3s 4P level. Electrical quenching by a 60-kc/sec field reduces the N2+ bands more sharply than the N2 bands or the N lines. Optical absorption and other measurements show that the concentrations of ground-state and low-lying metastable atoms are little affected by this afterglow or by its quenching.
Absolute Infrared Intensities in Some Crystalline Hydrogen Halides
Authors: Friedrich H. Bruce , Person Willis B.
Published: January 2005

Absolute intensities of the fundamental vibrational bands of HCl and HBr have been measured in the absorption spectrum of crystalline films. The path length has been determined from the interference fringes of the transmitted light as the film is deposited on a window, following the technique of Hollenberg and Dows. The measured integrated molar absorption coefficients B are 24 000±3000 and 17 600±1200 darks (cm—1cm2/mM), respectively, for HCl and HBr. These values are larger than the gas phase intensities by factors of 6 and 13, respectively. Such large intensification of an X—H stretching vibration is consistent with the large frequency shift and is characteristic of hydrogen-bonded crystals. The results are compared with those from other hydrogen-bonded systems. Furthermore, the high intensities are consistent with those required by Hornig and Hiebert using the transition dipole—transition dipole model to explain the observed intermolecular force constants. However, it is likely that other terms contribute as much to these constants. Finally, the formalism used by Hexter to express the frequencies in molecular crystals is modified slightly so that hydrogen-bonded crystals can be treated.
Polarization of the Triplet—Triplet Absorption Spectrum of Some Polyacenes by the Method of Photoselection
Authors: El-Sayed M. A. , Pavlopoulos T.
Published: January 2005

The method of photoselection is modified to measure the polarization of the triplet—triplet absorption of naphthalene-d8, phenanthrene, and chrysene. The three main bands of a given molecule are found to be similarly polarized. This fact, together with other spectroscopic arguments, excludes the previously proposed assignment that the absorption belongs to more than one electronic transition. While the absorption in naphthalene-d8 is found to be perpendicular to the 1La band (Platt's notation), that in phenanthrene is found to be parallel. Since the 1La band results from a transition which is polarized along the short axis in naphthalene-d8 but is polarized along the long axis in phenanthrene, the triplet—triplet absorption must then be polarized along the long axis in both molecules. Because the lowest triplet level of each molecule belongs to the 3La level, the excited triplet is assigned to the 3Ka level which corresponds to 3B3g— in naphthalene and 3B2— in phenanthrene (the y and z axes are taken as the long and short molecular axes respectively). Therefore, the 3Ag— level in naphthalene must have an energy which is either higher than 6.6 eV or lower than 4.2 eV. In either case, it shows that theoretical predictions of Pariser are good for the 3B3g— level but off by more than 1 eV for the 3Ag— level.
Microwave Spectrum, Structure, and Dipole Moment of ``Cis''-N2F2
Authors: Kuczkowski Robert L. , Wilson E. Bright
Published: January 2005

The microwave spectra of the F14N14NF and F15N14NF isotopic forms of the ``active'' isomer of N2F2 are reported and from this the structure is derived as planar and cis with the following structural parameters: d(NN)=1.214±0.005 Å, d(NF)=1.384±0.01 Å, ∠FNN=114.5±0.5°. A dipole moment of 0.16±0.01 D has been evaluated from the rotational Stark effect. Transitions of the molecule in an excited vibrational state are reported. From relative intensity measurements of this state, a vibrational frequency of 300±35 cm-1 is estimated. A method is demonstrated enabling the ratio of nuclear spin statistical weights of two transitions to be determined from the growth rate of their intensities with increasing Stark modulation voltage.
Open-Shell SCF Triplet-State Energies of Polyacenes
Authors: Goodman Lionel , Hoyland James R.
Published: January 2005

Using Roothaan's open-shell procedure lowest triplet-state excitation energies are computed for several polyacenes. The results indicate that single determinant wavefunctions constructed from ground-state (closed-shell) SCF orbitals give poor descriptions of the triplet states, leading to errors of up to ½ eV in the energy. The triplet-state orbitals are given. Comparison of these calculations with Pariser's CI computations suggests that significant correlation has been introduced into the CI excited state description, but not into the ground state.
Chemiluminescent Reactions Involving Atomic Oxygen and Nitrogen
Authors: Young Robert A. , Sharpless Robert L.
Published: January 2005

The emission excited in the association of atomic oxygen and nitrogen has been studied in a fast-flow low-pressure system by photoelectric and spectroscopic methods. The absolute rates of excitation of the products of these associative processes have been measured, and the effects of added quenching gases have been investigated. Specific excitation processes consistent with the present observations are discussed.
Ionization on Tungsten Single-Crystal Surfaces
Authors: Reynolds F. L.
Published: January 2005

Surface ionization of atomic beams of strontium or calcium from the [110] and the [111] directions of tungsten was studied mass-spectrometrically. Results consistent with the Saha—Langmuir relation indicate that the method is applicable for the determination of first ionization potentials or work functions. A value for the work function of the [110] direction is 5.41±0.04 eV. A value for the [111] direction of tungsten is 4.49±0.04 eV.
On the Nature of the Crystal Field Approximation. II. Numerical Results
Authors: Berger R. T. , Herzfeld C. M.
Published: January 2005

Herzfeld and Goldberg developed a modified molecular orbital technique to show the effect of the neglect of wavefunction overlap and electron exchange on the results of crystal field theory. They gave formal results for the interaction of a hydrogen atom in a 2p state and a hydrogen molecule in the ground state for two different nuclear configurations. In one case, the atom nucleus lies on the perpendicular bisector of the molecule axis, and in the other all three nuclei lie on a line. These results have been evaluated analytically and numerically for a wide range of internuclear distances. Values for crystal field splitting parameters obtained by the new MO method cross over those obtained by crystal field theory at a distance between the atom and perturbing molecule of about 4-bohr radii (2A). At this distance, the result of the modified MO calculation is primarily determined by overlap and exchange contributions. At larger distances, where exchange and overlap go to zero, both methods give the classical expression for the interaction of two quadrupoles.
Absorption Coefficients of Nitrogen in the 1000–580 Å Wavelength Region
Authors: Huffman R. E. , Tanaka Y. , Larrabee J. C.
Published: January 2005

Absorption coefficients of molecular nitrogen have been measured with a photoelectric scanning technique using an intense, stabilized Hopfield helium-continuum light source as background. These measurements differ from previous investigations where line sources were used as background. The measurements have been done with an instrumental bandwidth of 0.5 Å over a pressure range of 0.040 to 0.17 mm Hg using an absorption cell placed behind the exit slit of a vacuum monochromator. Corrections were made for the pressure gradient in the flow-absorption cell, for the scattered light, and for fluorescence. From 1000 to 796 Å, the first ionization threshold (N2+, X 2Σg+), a number of sharp, intense bands are present with no evidence of a dissociation continuum. Below 796 Å, the ionization continuum appears to rise slowly to 400 cm—1 at 742 Å (N2+, A 2IIu), but this region is also crowded with many intense bands. Most of these appear to be strongly preionized. Between 742 Å and the threshold of the B 2Σu+ state at 661 Å, the ionization continuum increases from roughly 400 to 780 cm—1, and the pre-ionized Hopfield Rydberg series is the main feature. At 661 Å, the absorption coefficient rises abruptly to 980 cm—1 and continues at approximately this constant value to 580 Å. The present results are compared whenever possible with previous measurements and discussed in relation to photo-ionization measurements. Application of this data to calculation of absorption processes in the upper atmosphere is discussed.
Deuteron Magnetic Resonance Study of Barium Chlorate Monohydrate
Authors: Chiba Takehiko
Published: January 2005

Quadrupole splitting of deuteron magnetic resonance was measured for a single crystal of Ba(ClO3)2·D2O. Quadrupole coupling, asymmetry parameter, and principal axis directions of the field gradient tensor were determined at 20° and at —130°C. eqQ/h=121.5±0.4 kc/sec, η=0.976±0.007 at 20°C, and eqQ/h=243.5±1.5 kc/sec, η=0.074±0.002 at —130°C. The field gradient at room temperature shows a rapid reorientation of the water molecule in a crystal. At room temperature, the spectral line exhibits fine structure due to coupling of two spins, which was utilized to determine the sign of eqQ in the present case.

The line broadening effect in the intermediate temperature region (—45°∼—121°C) was measured and was used to obtain the reorientation rate at various temperatures. The barrier to reorientation of 6.6 kcal/mole was obtained from the comparison of the experimentally determined reorientation rate with that calculated from a tunneling process through a hindering barrier, or that of 6.5 kcal/mole from classical process. The temperature dependence of quadrupole splitting was also measured and the oscillation frequencies were derived for the torsional motion of D2O. It was found that the quadrupole coupling for a vibrationless molecule is about 12% less than that of a free molecule.

The observed eqQ, principal axis directions of field-gradient tensor are discussed in connection with the disposition of atoms in the crystal. A qualitative explanation is given for the change of eqQ from a free molecule to that in the crystal as due to the effect of the hydrogen-bonded oxygen atom.
Photo-Ionization Efficiency Curves. Measurement of Ionization Potentials and Interpretation of Fine Structure
Authors: Nicholson A. J. C.
Published: January 2005

A method is described for measuring photo-ionization efficiency (PE) curves over the energy range 9–14 eV. The method is experimentally easier than measuring the photo-ionization cross section and gives essentially the same result. PE curves are given for Xe, O2, and NO and first ionization potentials are determined; Xe, 12.129±0.002 eV; O2, 12.065±0.003 eV; and NO, 9.250±0.005 eV. It has been established that steps in the PE curve of NO give a quantitative measure of the energies of the vibrational levels in the NO+ ion and that peaks in the curves of all three gases correspond to neutral levels that auto-ionize. The probability laws for ionization and auto-ionization are discussed.
Electrophilic Character of the Hg 6(3P1) Atom and the Mechanism of Electronic Energy Transfer in Mercury Photosensitization
Authors: Rousseau Yves , Strausz O. P. , Gunning H. E.
Published: January 2005

It is shown that in mercury-6(3P1)-photosensitized reactions the Hg 6(3P1) atom behaves as a distinctly electrophilic reactant in most of its reactions and that the H/D isotope effect exhibited by some paraffin molecules with respect to the quenching reaction can be satisfactorily estimated from transition-state theory. This interpretation of the data, taken in conjunction with the results of some recent primary process studies, point up the chemical nature of electronic energy-transfer processes in these systems in that the transfer reaction proceeds through the formation of a well-defined transition complex involving both substrate molecule and sensitizer atom.
Formation of Negative Ions in SbCl3
Authors: Grob Victor E.
Published: January 2005

The formation of negative ions in SbCl3 by low-energy electrons has been investigated using a modification of a total ionization tube which allows the ion species to be determined and prevents contact potentials from affecting the electron energy in the collision region. The identification of the specific reaction taking place was obtained by modifying the total ionization tube to operate as a magnetron beyond cutoff. The mass of the ion species was then determined from an analysis of the ion current to the collector as a function of the applied axial magnetic field and the ion collector bias. The electron-energy distribution had an effective width at half-height of approximately 0.07 eV which was obtained using the retarding potential difference method. With the apparatus the most probable initial ion reaction was SbCl3+e→SbCl2+Cl—. The value of the dissociative capture cross section at the point of ion apparance was (1.8±0.3) × 10—16 cm2, and the minimum energy of the electron for the appearance of ions was approximately 0.01 eV at a gas temperature range 25°—50°C. The dissociation energy for the reaction SbCl3→SbCl2+Cl was 3.69±0.15 eV.
Yield of ``Free Ions'' in Gamma-Irradiated Liquid Saturated Hydrocarbons
Authors: Freeman G. R.
Published: January 2005

When a hydrocarbon is subjected to ionizing radiation, some of the electrons that are ejected from the molecules escape the electric field of their parent ions. An ``escaped electron'' and its parent ion can diffuse independently of each other, so they may be considered as free ions. The number of electrons that escape their parents per hundred electron volts of energy absorbed by the system, G(esc e—), is approximately 0.2. This value was determined by conductance measurements and is probably accurate to within a factor of 50%.

From numerical analysis of delta-ray energy spectra, it appears that secondary electrons with energy greater than 30 or 40 eV can escape from their parent ions.
Fluoride Interference Films on Uranium Dioxide. I. The Kinetically Derived Optical Equation
Authors: Ellis W. P.
Published: January 2005

At the interfaces of absorbing dielectrics reflected light undergoes an abrupt phase change other than zero or π. For a transparent interference film on an absorbing dielectric substrate this change has the effect of shifting the wavelength of maximum interference toward a higher value. From the spectrophotometrically determined rates of film formation an extrapolation to zero time (zero thickness) gives the fractional wavelength shifts directly. Values are obtained experimentally for the hydrofluorination reaction of uranium dioxide and are compared with values calculated from optical theory.
Application of Configuration Interaction to the 23S State of Helium. II
Authors: Davis H. L.
Published: January 2005

The configuration interaction method is applied to the nonrelativistic 23S state of the helium atom. It is shown, by variationally adjusting the effective charges of the angular configurations, that no radial readjustment occurs for this state. The final set of 80 configurations then gives an energy of —2.1752259 a.u., recovering 27% of the energy difference between our best previous configuration-interaction value and the extrapolated value of Pekeris. A discussion is then given concerning the relative merit of the configuration interaction method and suggestions given for its future application to the 23S state of the two-electron system.
Delayed Fluorescence of Solid Solutions of Polyacenes. II. Kinetic Considerations
Authors: Azumi Tohru , McGlynn Seán P.
Published: January 2005

Delayed fluorescence has been observed at 77°K from rigid-glass solutions of some aromatic hydrocarbons and their halo derivatives. The intensity of the delayed fluorescence is proportional to the square of the phosphorescence intensity. The decay of delayed fluorescence in all cases may be represented as the sum of two first-order processes; the lifetime of the longer-lived component varies between 1/2↔1/5 that of the phosphorescence while the lifetime of the shorter-lived component varies between 1/10↔1/50 that of phosphorescence. The intensity of delayed fluorescence observed from a solution of a given compound varies as the ratio φfφp2/k3*2, where φf and φp are fluorescence and phosphorescence quantum yields, respectively, and where k3* is the emissive phosphorescence rate constant. Phosphorescence decay exhibits a slight nonexponentiality only in the case of those solutions where the delayed fluorescence is especially strong. Delayed fluorescence is spectrally identical, within the limits of spectrograph resolution available to us, with ordinary fluorescence. The above facts may only be interpreted by a kinetic mechanism which involves a triplet—triplet annihilation process, this mutual annihilation resulting in the eventual production of the singlet excited state of one of the partners. Some ancillary hypotheses are required to interpret the shorter-lived component of the delayed fluorescence, and a kinetic flowsheet representative of the energy-transfer processes involved in the production of delayed fluorescence is proposed.
Polymer NMR Spectroscopy. X. The Use of H1–H1 Spin Decoupling in the Elucidation of Polymer Structure
Authors: Bovey F. A. , Anderson E. W. , Douglass D. C. , Manson J. A.
Published: January 2005

High-resolution NMR spectroscopy of vinyl polymers in solution is an effective means of determination of the stereochemical configuration of their chains. In polymers having only a single α substituent, however, spin coupling of α and β protons complicates the interpretation of the spectrum considerably and also makes it difficult to observe those stereoisomeric sequences which are present as minor components. Decoupling of the α- and β-proton spins has been found to be helpful in the interpretation of the spectra of polyvinyl chloride, polyvinyl fluoride, and polyvinyl methyl ether. It is not helpful for polyvinyl acetate in carbon tetrachloride, since here the chemical shift of the α and β protons is not sensitive to stereochemical configuration.
Spectroscopic Evidence for Complex Formation between Carbon Tetrachloride and Aromatic Hydrocarbons
Authors: Anderson Ralph , Prausnitz J. M.
Published: January 2005

Spectrophotometric data in the ultraviolet range at 25°C indicate that carbon tetrachloride forms a weak charge-transfer complex with benzene and with mesitylene. For 1:1 complexes the equilibrium constants are, respectively, 0.009±0.004 and 0.113±0.044 liter/g·mole.
Molecular Rotation and Ortho—Para Nuclear Spin Conversion of Water Suspended in Solid Ar, Kr, and Xe
Authors: Redington Richard L. , Milligan Dolphus E.
Published: January 2005

Additional data supporting the nearly free rotation of the water molecule trapped in a rare-gas lattice are presented. Ortho—para spin conversion is strongly induced by adding O2 to the matrix. A simple model is suggested which correlates the intensities observed for H2O, HDO, and D2O suspended in Ar, and which estimates the rate of nuclear spin conversion to within a factor of 5 or 10. The majority of the water molecules occupy substitutional sites in the lattice obtained by removing a single rare-gas atom.

Several sharp, intense lines are tentatively assigned to the H bonded OD stretch of HDO and D2O dimers in Ar. They contrast markedly with the corresponding broad band of the OH stretch.
Chemistry of Positive Ions. III. The Radiation Chemistry of Solid n-Hexane at 77°K
Authors: Kevan Larry , Libby W. F.
Published: January 2005

The mechanism of the chemical effects of ionizing radiation on solid straight-chain saturated aliphatic hydrocarbons such as polyethylene was studied by use of n-hexane. This hydrocarbon was short enough to allow analysis of the cross-link C12 products and of the hexenes formed. It was thought to be long enough to serve as a legitimate substitute for polyethylene. In any case, the yields of H2, olefines, and cross linkages were very similar in the two systems and we believe the mechanistic implications found here for solid n-hexane at 77°K should apply even to polyethylene.

The results indicate: (a) the active species is the original ion radical produced by the ionizing radiation (Co60 gammas); (b) the ion radical reacts before relaxing to redistribute the positive charge or to isomerize in any way, and the products show that there are three primary ions formed corresponding to the first, second, and third carbon atoms in the chain; (c) the ion radical reacts with nearest neighboring groups to bond and release H2, thus forming olefines by reaction with neighboring C atoms in the same molecule four times out of five, but reacting with neighboring chains to form C12 dimers one time out of five; the dimers being only the five hydrocarbons possible by close-neighbor interaction: the 1,1 interaction being n-dodecane; the 1,2 being 5-methylundecane; the 2,2 being 5,6-dimethyldecane; the 2,3 being 4-ethyl-5-methylnonane; the 3,3 being 4,5-diethyloctane and no others; (d) the principal mechanism of the fast interaction of the primary ion is the direct elimination of H2 and formation of a bond due to charge exchange attraction between the primary ion and the neutral group with which it interacts; (e) the second most important mechanism is the abstraction of H to form the electronically saturated analog of CH5+ which when neutralized eliminates H2 and leaves a free radical to combine with the neighboring free radical left by the H abstraction; (f) free radicals seem to play a minor role in the solid hydrocarbon, n-hexane.
Theory of the Thermal Accommodation Coefficients of a Diatomic Gas
Authors: Feuer P.
Published: January 2005

A quantum-mechanical theory of the thermal accommodation coefficient is discussed for a diatomic gas whose molecules can possess internal energy of rotation as well as translational energy. Expressions are obtained, in terms of transition probabilities, for αt, the accommodation coefficient associated with the change in translational energy of a beam of gas molecules reflected from a solid surface, and αi, the accommodation coefficient associated with the change in internal energy of the gas molecules. The gas molecules are considered as rigid plane rotators; and, on striking the surface, a gas molecule experiences a change in rotational and translational energy, while an atom of the solid loses or gains vibrational energy. Some general conclusions are drawn concerning αt and αi and their relation to each other, and a special case is considered.
On the Effect of the Bond Angle in the Electron Spin—Spin Interaction. Methylene Derivatives
Authors: Higuchi Jiro
Published: January 2005

The effect of the bond angle on the electron spin—spin interaction has been investigated for methylene derivatives, especially methylene and phenylmethylene, in which a bent methylene bond is possible.
An Extended Hückel Theory. I. Hydrocarbons
Authors: Hoffmann Roald
Published: January 2005

The Hückel theory, with an extended basis set consisting of 2s and 2p carbon and 1s hydrogen orbitals, with inclusion of overlap and all interactions, yields a good qualitative solution of most hydrocarbon conformational problems. Calculations have been performed within the same parametrization for nearly all simple saturated and unsaturated compounds, testing a variety of geometries for each. Barriers to internal rotation, ring conformations, and geometrical isomerism are among the topics treated. Consistent σ and π charge distributions and overlap populations are obtained for aromatics and their relative roles discussed. For alkanes and alkenes charge distributions are also presented. Failures include overemphasis on steric factors, which leads to some incorrect isomerization energies; also the failure to predict strain energies. It is stressed that the geometry of a molecule appears to be its most predictable quality.
Effects of Isotopic Labeling and Molecular Structure on Probability of Ionization by Electron Impact
Authors: Meyerson Seymour , Grubb H. M. , Haar R. W. Vander
Published: January 2005

Isotope effects have been reported on probability of ionization of molecules by photons, by excited rare-gas atoms, and by beta rays. Such effects furnish evidence that ionization occurs largely as a secondary process in competition with nonionizing processes following primary excitation to an energy level above the ionization potential. Measurements of total ion current produced in a mass-spectrometer source show similar effects for the case of ionization by 70-V electrons. Experimental support has been obtained also for the corollary that probability of ionization depends upon molecular structure and is not simply, as has been postulated, a constitutive property of the atoms.
Ion—Solvent Interaction. II. Partial Molar Volume and Electrostriction: a Thermodynamic Approach
Authors: Padova J.
Published: January 2005

The thermodynamic treatment of a fluid in an electrostatic field is applied to the calculation of the partial molar volume of electrolytes in aqueous solutions at infinite dilution. The electrostriction may be interpreted in terms of a general solvation number that accounts for the total solvent—solute interaction. This treatment is further extended to the free energy and entropy of solvation in terms of the same intrinsic radii, giving reasonable agreement with literature data.
Pi Electronic Structure of the Benzene Molecule
Authors: Moskowitz J. W. , Barnett M. P.
Published: January 2005

A configuration-interaction calculation in a molecular orbital basis has been performed for the benzene molecule. The Goeppert-Mayer and Sklar core approximation has been assumed. All three- and four-center integrals have been accurately computed.
Improved Calculation of Quasiequilibrium Reaction Rate Constants
Authors: Lin S. H. , Eyring Henry
Published: January 2005

The method of steepest descents has been applied to the calculation of the total number of quantum states of a system of harmonic oscillators. The corresponding rate expressions of unimolecular reactions have also been derived.
Lattice Work Performed by Excited Molecules
Authors: Bhaumik M. L. , Hardwick R.
Published: January 2005

The noncoincidence of the 0–0′ and 0′—0 absorption and fluorescence bands in many complex organic molecules in solution has been attributed to work of reorientation of solvent dipoles under the influence of the changed dipole of the excited solute. It has been found experimentally that the effect usually diminishes in low-temperature rigid glasses, but whether this is due to the prohibition of molecular reorientation or actually represents a temperature-induced spectral change is not uniquely established in this type of experiment. We have separated the effects of viscosity and temperature by studying solutions of fluor molecules in polymers. As might be expected, the viscosity effect far outweighs that of temperature.
ESR Study of Polyazine Anions
Authors: Stone Ellery W. , Maki August H.
Published: January 2005

Electron spin resonance measurements have been made on dimethyl sulfoxide solutions of the anion radicals of s-tetrazine, pyridazine, phthalazine, and phenazine, as well as the diprotopyrazine cation radical. The radicals were generated by constant potential electroreduction of the parent compound at a mercury pool cathode within the microwave cavity. Complete assignment of the hyperfine coupling constants to positions of phthalazine anion was made by selective deuteration and the help of a spectral synthesis program. Satellites due to the C13 hyperfine interaction of pyrazine anion have been observed, and the coupling constant measured. The mechanism of N14 hyperfine interactions in polyazine anion radicals is discussed in terms of earlier theories of C13 interaction. We find that π-electron spin density on nearest-neighbor N atoms affects aN strongly, whereas on nearest-neighbor C atoms it does not. Values for several empirically determined spin-polarization parameters are reported.
Cyclotron Resonance in Slightly Ionized Gases
Authors: Fehsenfeld Fred C.
Published: January 2005

The conductivity of a slightly ionized gas in a uniform magnetic field has been obtained from the solution of the Boltzmann equation for cases in which the collision frequency between electrons and neutral particles are dependent on the electron velocity. The line shapes of the cyclotron resonance absorption of energy from a high-frequency electric field and the derivative with respect to the magnetic field of the resonance absorption have been computed. Also the relationship between the linewidth of the above curves and the collision frequency was obtained.

The absorption of 9 kMc/sec microwave energy by the weakly ionized thermalized afterglows of helium, argon, oxygen, and carbon dioxide near cyclotron resonance has been measured experimentally. From these measurements the collision frequencies for thermal electrons with He, Ar, O2, and CO2 have been obtained. These collision frequencies are 2.0+0.2×108, 1.6±0.5×108, 1.7±0.2×108, and 24+2×108, respectively, for the above gases at 300°K and 1 mm Hg pressure.
Energy of the Lithium Atom by the Least-Squares Local Energy Method
Authors: Gimarc B. M. , Frost A. A.
Published: January 2005

The least-squares local energy method is applied to the lithium atom ground state. For a correlated wavefunction of 51 terms the calculated energy is —7.4653 hartrees compared with the exact nonrelativistic value of —7.4781 hartrees. Important limitations of the method are discussed and possibilities for avoiding them are proposed.
Diffraction Studies of Photochemical Decomposition of Azides. I. X-Ray and uv-Induced Lattice Constant Changes in TlN3
Authors: Krause Brigitte H.
Published: January 2005

Diffraction methods were applied to study irradiation and annealing effects on TlN3. Crystallographic lattice constant and cell volume changes upon x-ray irradiation were determined as function of irradiation time and radiation intensity. From the character of these curves some conclusions were drawn about the physical processes causing the effects. The reversibility of these processes was studied by annealing experiments at various temperatures and in both air and helium atmospheres.

Preliminary studies of radiation damage on uv-irradiated samples were carried out in order to relate the diffraction results to the TlN3 absorption spectrum and photoconductivity data.
Proton Chemical Shifts in Polysubstituted Benzenes
Authors: Martin John S. , Dailey B. P.
Published: January 2005

The ring proton chemical shifts of an extensive series of polysubstituted benzenes may be represented, with an accuracy of about 0.1 part per million, as simple sums of substituent shielding constants, except in the case of ring protons next to substituents which are ortho to one another.

The small, uniform deviations from additivity of the 46 shifts measured in a series of para disubstituted benzenes are well represented by a linear variation, so that the chemical shift of proton 2 in a 1,4-substituted benzene may be expressed as δ2=d0(R1)+γ(R1)dm(R4).The polarizability γ decreases as d0 increases.

The values of the shielding parameters d are consistent with a mechanism dominated by the pi-electron charge distribution, although other effects are present, especially at the meta position, which cannot be accounted for in a consistent manner. It can be shown that the molecular-orbital theory of substituent interaction with the pi-electron system can yield a variation of polarizability with charge density of the order of magnitude of that observed; however, the symmetry of this variation is inconsistent with a single-parameter interaction mechanism.