bluuebunny/crossref_metadata_2025 huggingface dataset:
Reaction of O(1D) with Nitrogen
Authors: DeMore W. , Raper O. F.
Published: January 2005

Dilute solutions of O3 in liquid N2 have been photolyzed at several wavelengths in the ultraviolet with light from a monochromator. Nitrous oxide is formed in low quantum yield by reaction of O(1D) with the N2 solvent. Addition of an inert diluent, argon, does not lower the quantum yield, showing that the reaction is not due to ``hot atoms'' and probably has zero activation energy. The effect of added O2 on the N2O quantum yield shows that O2 reacts with O(1D) 4.5 times faster than does N2.

The wavelength dependence of the N2O quantum yield suggests that the O(1D) quantum yield in the primary step of O3 photolysis is constant below about 3000 Å, but has a lower and apparently decreasing value above 3000 Å. In addition, exchange experiments with O236 show that the O(1D) yield is approximately unity at 3000 Å.

The principal reaction of O(1D) with N2 is O(1D)+N2+M→N2+O(3P)+ M, and not O(1D)+N2+M→N2O+M. The low efficiency of N2O formation is due to a feature of the N2O potential energy surfaces which allows decomposition of the excited association complex to N2+O(3P), in the course of stepwise vibrational deactivation.
Molecular and Valence Structures of Complexes of Cyclo-Octatetraene with Iron Tricarbonyl
Authors: Dickens Brian , Lipscomb William N.
Published: January 2005

Structure determinations by x-ray diffraction methods indicate that Fe(CO)3 units are bonded to a butadiene type of residue in C8H8Fe(CO)3(I), and in (OC)3FeC8H8Fe(CO)3 (II), where the two Fe(CO)3 units are on opposite sides of the C8H8 ring. The dihedral C8H8 ring in (I) and the chair C8H8 ring in (II) are previously unknown and unsuspected geometries for cyclo-octatetraene.

Crystals of (I) have symmetry Pnam, within experimental error, with four molecules in a unit cell defined by the parameters a=6.54, b=13.46, c=11.50 Å. Crystals of (II) are of symmetry P21/n, with four molecules in a unit cell which has parameters a=12.52, b=13.38, c=8.86, and β=111°. Final values of R=Σ | | F0 | — | Fc ‖/Σ | F0 | are 0.09 for (I) and 0.10 for (II) for all observed reflections.

The bonding of Fe to the butadiene-like residues is discussed.
Dispersion at Millimeter Wavelengths in Methyl and Ethyl Alcohols
Authors: Saxton J. A. , Bond R. A. , Coats G. T. , Dickinson R. M.
Published: January 2005

This paper describes measurements, made by a free-wave technique, of the dielectric properties of methyl and ethyl alcohols at wavelengths of 3.11, 4.30, and 9.04 mm. The observations are analyzed in relation to the theory of dispersion and, in conjunction with previously existing measurements at adjacent wavelengths, provide evidence of a second dispersion region at radio frequencies in each liquid in addition to the main one normally associated with Debye-type dipole-rotation phenomena.
Electronic Calculation on NH3. Harmonic Force Constants, Infrared and Ultraviolet Spectra
Authors: Bratož S. , Allavena M.
Published: January 2005

The harmonic force constants, infrared and ultraviolet spectra of NH3, are studied theoretically. The calculation is based on a single-center configuration interaction wavefunction; the corresponding energy is differentiated analytically. The calculated force constants are discussed, particularly the interaction force constants. The theoretical infrared spectra of NH3 and ND3 agree reasonably well with the observed spectra. The ultraviolet spectrum of NH3 is also studied; the lowest singlet—singlet transitions are found to be 1A1←1A1 and 1E←1A1 (in C3v notation).
Numerical Evaluation of the van der Waals Forces of Interaction between Two Macroscopic Bodies
Authors: Devereux O. F. , de Bruyn P. L.
Published: January 2005

The Lifshitz function Φ(ε10, ε20) is evaluated numerically over a wide range of static dielectric constants (ε10, ε20) of the interacting bodies. This function enables the calculation of the van der Waals interaction force between two macroscopic bodies separated by short distances under certain restrictive conditions as to distance of separation and temperature.
Use of Gaussian Functions in the Calculation of Wavefunctions for Small Molecules. II. The Ammonia Molecule
Authors: Reeves C. M. , Harrison M. C.
Published: January 2005

This paper reports further work on wavefunctions using Gaussian functions. Restricted optimization of the parameters in calculations on the nitrogen atom, using eight functions, and the ammonia molecule, using 14 functions, results in a calculated binding energy of 0.4774 a.u., although total energies are in error by about three times this. Suggestions are given for the simplification of calculations using large bases.
Kinetics of the Reaction of HI with Ethyl Iodide and the Heat of Formation of the Ethyl Radical
Authors: Hartley D. B. , Benson Sidney W.
Published: January 2005

The kinetics of the reaction between EtI and HI have been studied in the temperature range 263° to 303°C using a spectrophotometric technique for the determination of I2. The mechanism obeyed is the following: I2⇌2I,  KI2I+EtI⇌ lim 21Et+I2,Et+HI⇌ lim 43EtH+I,,which has the rate law (neglecting Step 4): d(I2)dt=k1k3KI212(EtI)(HI)(I2)12k2(I2)+k3(HI).. Decomposition of EtI by unimolecular elimination of HI is negligible.

A differential method was employed to determine the rate constants k1 and the ratio k2/k3. The Arrhenius parameters of these constants were evaluated experimentally and combined with known thermodynamic data to give the parameters of the individual constants k2, k3, k4. As with other I2 molecule systems, the A factors of Reactions (1) and (4) are high, being approximately equal to collision frequencies.

With the assumption E2=0.2 kcal and the experimental activation energy E1, the C–I bond-dissociation energy in EtI is found to be 52.9±1.0 kcal at 25°C. The heat of formation of the ethyl radical as determined here [ΔHf°(Et)=25.3±1.2 kcal] indicates the C–H bond energy in ethane to be 97.7±1.2 kcal. These values agree well with independent estimates.
Thermodynamic Properties of Silicon Tetrafluoride from 15°K to Its Triple Point. The Entropy from Molecular and Spectroscopic Data
Authors: Pace E. L. , Mosser J. S.
Published: January 2005

The heat capacity of silicon tetrafluoride has been measured from 15° to 194°K for a sample of 99.97 mole % purity. The solid—liquid—vapor triple-point temperature and pressure were, respectively, 186.35°K and 1679.3 mm. The heat of fusion and heat of vaporization at the triple point were found to be, respectively, 2242 and 3555 cal/mole. The vapor pressure of the solid has been measured from 163° to 186.35°K and the data fitted to the equation log10Pmm=−5.5025–894.93/T+5.9593log10T.Only one vapor-pressure point other than the triple point itself was taken for the liquid. The entropy of silicon tetrafluoride in the ideal gas state at a pressure of one atmosphere and a temperature equal to the triple-point temperature of 186.35°K was found to be 59.85±0.20 cal/(mole °K). This value agrees within the experimental uncertainty with the value of 60.037 cal/(mole °K) calculated theoretically from the molecular parameters and fundamental frequency assignment.
Relative Partial Wave Theory of Diatomic Molecules
Authors: Temkin A.
Published: January 2005

The method of expanding the Hamiltonian in (relative) partial waves and introducing similarly expanded but truncated series as approximate solutions is utilized in the case of (H2)+ as a prototype of diatomic molecules. Thirteen states have been examined at four internuclear separations and results compared to exact results. In particular, oscillator strengths have been computed, and various properties of the approximate solutions are exhibited which make this method potentially very useful especially for some astrophysical applications. A simple modification of the theory can be made which ensures that the oscillator strengths satisfy the sum rules.
Thermoelectric Power in Nonstoichiometric α-Nb2O5
Authors: Janninck R. F. , Whitmore D. H.
Published: January 2005

Thermoelectric power measurements have been made on nonstoichiometric α-Nb2O5 over the temperature range from 300° to 1270°K. The measurements show that, for all compositions in the single-phase, α-Nb2O5—x region (0.0012≤x≤0.1545), the majority charge carriers are electrons. These thermoelectric power data have been interpreted in terms of a simple semiconductor exhibiting conduction in a narrow d band with the conduction electrons being assigned an effective mass equal to four times that of the rest mass.
Removal of Residual Splitting in Nuclear Magnetic Double Resonance
Authors: Anderson W. A. , Nelson F. A.
Published: January 2005

Double resonance experiments have been used as an aid in simplifying complex nuclear magnetic resonance spectra. However, in all except the simplest cases there is a residual splitting due to the coupling to the irradiated group even at relatively large irradiating fields. It is shown that this residual splitting can be greatly reduced or eliminated by a modulation of the frequency of the irradiating field. The conditions necessary to minimize the residual splitting are derived and discussed. The technique is illustrated with two examples.
Dissociative Ionization of CO by Ion Impact
Authors: Giese Clayton F. , Maier William B.
Published: January 2005

Cross sections for the reactions He++CO→C++O+He, Ne++CO→C++O+Ne, and Ar++CO→C++O+Ar are studied as functions of ion kinetic energy. The first reaction exhibits the behavior expected for an exothermic reaction. The latter two prove to be endothermic and to have onsets which are surprisingly sharp. The experimental thresholds are in good agreement with values calculated from the well-accepted D(CO) = 11.11 eV. It appears that the technique used may prove to be useful for determining unknown bond-dissociation energies.
Nuclear Relaxation in Molecular Liquids Containing Free Radicals
Authors: Gutowsky H. S. , Tai Julia Chow
Published: January 2005

Radio-frequency pulse methods have been used to investigate the solvent-proton and fluorine nuclear relaxation mechanisms in solutions of the organic free radicals α,α′-diphenyl-β-picrylhydrazyl (DPPH) and of di-tertiary-butylnitroxide (DTBN) in molecular liquids. The protons 1/T1 and 1/T2 depend linearly upon DPPH concentration in benzene, as predicted for relaxation governed by nucleus—free-radical interactions. The proton T1/T2 ratio is close to unity (∼1.2), at 28 Mc/sec and 21°C, for six different solvents containing DPPH, and eight with DTBN, indicating the predominance of nucleus—electron, dipole—dipole relaxation. The fluorine T1/T2 ratio is about 1.7 for DPPH and 1.5 for DTBN solutions in 1,3,5-trifluorobenzene and in hexafluorobenzene, indicating an appreciable hyperfine interaction between solvent fluorines and the free-radical odd electron. The temperature dependences of the proton and fluorine relaxation in these solutions, and in benzene solutions of DPPH and of DTBN correspond to apparent activation energies of about 2 kcal/mole for the motions governing the relaxation. The frequency dependences, between 3.74 and 36 Mc/sec at 21°C, of the nuclear relaxation in the solutions do not agree with relaxation characterized by only one correlation time. It is proposed that the free radicals are but weakly solvated and that the relaxation results from a combination of translational and rotational motions and, for fluorine, the AI·S interaction.
Mean Dimensions of Macromolecular Coil in Laminar Flow
Authors: Peterlin A.
Published: January 2005

By combining the measurements of the amount of streaming birefringence and of extinction angle one obtains the mean coil expansion h/h0 of the unbranched linear macromolecule in laminar flow. It turns out to be less than expected for a perfectly flexible model in good agreement with other evidence. This determination is independent on the molecular model and merely requires that the average optical anisotropy is proportional to the mean square of the end-to-end distance of the macromolecule.
EPR Study of Impurity-Related Color Centers in Germanium-Doped Quartz
Authors: Mackey John H.
Published: January 2005

Since aluminum and germanium are two of the most easily incorporated impurities in crystalline quartz, the relationship of the color centers produced by x irradiation to these elements has been studied extensively. Previous work based on irradiation at 300°K has indicated that one type of electron-deficient center is produced at aluminum, two kinds of electron-excess centers are associated with germanium, and local charge neutrality is maintained by the insertion of an interstitial Na+ or Li+ ion at the germanium site. We have studied this system after irradiation at 77°K by conventional methods of EPR spectroscopy (9500 Mc/sec) and have discovered a new set of low-temperature centers associated with these impurities. By identification of nuclear hfs and modification of the interstitial content through diffusion in an electric field, it is established that the same number of species is produced under these conditions but that the interstitial is located at the aluminum site. Detailed observations on the g tensors and hfs of the germanium centers are reported while observations on the aluminum centers are limited to the field orientation H ∥ c. By warming the crystals, efficient conversion of the low-temperature centers to the high-temperature forms is produced in crystals containing Na+ and Li+ for charge compensation. All low-temperature forms are bleached completely by warming in samples in which the alkali ions have been replaced by H+, which is known to have a small mobility. While detailed models of all centers are not suggested, enough information was obtained to establish the relationship between the low- and high-temperature forms. The experiments are correlated with optical results presented in an accompanying paper.
Two-Center Integrals over Solid Spherical Harmonics
Authors: Geller Murray
Published: January 2005

One-electron, two-center integrals (and the corresponding one-center case) are evaluated for integrals of the type ∫ [N,L,M]arbN′PL′|M′|(cosθb)rbL′+1{cos|M′|φbsin|M′|φb}dτarising in electromagnetic interactions. The Fourier convolution theorem method is employed and specific results are obtained for N′=0 and N′=2 in terms of an F function and recursion formulas. All cases up to L′=3 are evaluated in terms of the F functions and in terms of elementary functions.
Vibrational Energy Exchange between N2 and CO. The Vibrational Relaxation of Nitrogen
Authors: Millikan Roger C. , White Donald R.
Published: January 2005

The vibrational energy exchange N2(v=1)+CO(v=0)=N2(v=0)+CO(v=1) should be fast, due to near resonance of the energy levels. We have studied the rate of this exchange relative to the rate of energy transfer from translational to vibrational degrees of freedom in a shock-heated mixture of 1% CO—99% N2. Vibrational relaxation of the CO is observed by its infrared emission near 2000 cm—1. The density change behind the incident shock is simultaneously observed with an interferometer and gives a measurement of the N2 relaxation time. In the 3200°—4200°K range both methods are applicable; they yield identical relaxation times within the data scatter of ±20%. In contrast, at 3600°K, the vibrational relaxation time of pure N2 is four times that of pure CO. The exchange reaction thus appears fast enough to make the vibrational temperatures of the N2 and CO equal during the vibrational relaxation of the mixture. In the 1900° to 5400°K range, our study gives vibrational relaxation times in seconds for pure N2 (p=1 atm), represented by log10 τ=102T—⅓—11.24. This agrees at high temperature with Blackman's data, but gives a somewhat different temperature dependence. Extrapolation of our data to lower temperatures indicates relaxation times an order-of-magnitude longer than given by ultrasonic experiments.
Magnetic Resonance of Mn2+-Doped LiF Crystals
Authors: Chang T. T. , Tanttila W. H. , Wells J. S.
Published: January 2005

The electron paramagnetic resonance of Mn2+ in powdered LiF was observed at X-band and room temperatures for various impurity concentrations. The highest concentration was examined at K-band and low temperatures to obtain additional information regarding the distribution of Mn2+ ions which were introduced chemically into the lattice in small amounts. In the highest concentration, the K-band spectra indicate that part of the Mn2+ goes into the powder in the form of clusters of Mn and F which are antiferromagnetic at helium temperatures. NMR linewidth measurements on the lithium nuclei at low temperatures are qualitatively explained by the antiferromagnetism.

The room-temperature data from the more dilute samples exhibit not only the expected hyperfine splitting but also a superhyperfine splitting. The hyperfine interaction of the Mn2+ ion was determined to be A55=90±2×10—4 cm—1, and the isotropic part of the superhyperfine interaction with each of the six fluorine nearest-neighbor nuclei was measured to be As=17.1±0.5×10—4 cm—1.

Comparisons between K-band spectra from chemically prepared powdered samples and single crystals grown from the melt indicate that the melt method is unsuitable for obtaining the solid solution required to examine the superhyperfine spectra.
Time-Dependent Perturbation—Variation Method
Authors: Yaris Robert
Published: January 2005

Through the use of the time-ordered perturbation expansion, an operator equation for the time-dependent perturbation problem, of the same form as occurs in the time-independent problem, is generated. Thus, a variational method can be used to study the time-dependent case as well as the time-independent case. This variational method is used to recover the Dirac expansion as an example of a solution in series form, and it is also used to develop a simple (approximate) analytic solution as an example of a solution in closed form.
Viscosity of Polymer Solutions
Authors: Peterson James M. , Fixman M.
Published: January 2005

In the expression for the viscosity of polymer solutions η=η0+[η]C+K[η]2C2+···, the Huggins constant K is calculated for hard spheres and for interpenetrable spheres of uniform segment density. For hard spheres K = 0.6909, and for soft spheres where K is larger, the dependence of K on the segment—segment interaction constant is given. Difficulties in the basic theory caused by the long range of hydrodynamic perturbations are resolved. The theory is approximate, in that the velocity field arising from Sphere 1 is assumed to vary slowly in the vicinity of 2, but within this approximation all orders of ``reflections'' are correctly summed.
Infrared Spectra of Molten Salts
Authors: Wilmshurst J. K.
Published: January 2005

An emission technique for the study of the infrared absorption spectra of high-temperature liquids is described, and absorption spectra obtained by this technique for silver chloride and sodium nitrate, using two possible sampling arrangements, are compared with those obtained from reflectivity data. Absorption spectra derived from infrared reflectivity data are presented for the systems LiF–KF, LiF–KF–ZrF4, and NaF–KF–ZrF4. Interpretation of these spectra is consistent with the assumption of a complex zirconium species in the latter systems.
Direct Determination of Intermolecular Potential Parameters from Scattering Phase Shifts
Authors: Sanders W. A. , Mueller C. R.
Published: January 2005

Numerical methods have been developed for the direct determination of the parameters of intermolecular potential functions from scattering phase shifts, using the WKB expression for the phase shifts. Four potential functions were investigated, ranging in sophistication from the simple square-well model to a function with five adjustable parameters. Although the complexity of the calculations increased as the potential function became more complicated, the availability of an IBM 7090 computer made it possible to use numerical methods with considerable success. The computing time was reduced to less than 15 sec per iterative cycle for the five-parameter potential.
Methane—Tritium System. I. Mass Spectra of Tritium-Substituted Methanes
Authors: Kandel Richard J.
Published: January 2005

The mass spectral pattern coefficients and sensitivities of the individual tritium-substituted methanes, CH3T, CH2T2, CHT3, and CT4, were computed from the mass spectra of mixtures of tritium and methane which were undergoing isotopic exchange. Isotope effects in the ionization and dissociation of the various molecules were determined and compared with those observed in deuterium-substituted compounds. The following isotope parameters were found: for CH3T, Γ=1.23, π=0.62; for CH2T2, Γ=1.53, π0.50; for CHT3, Γ=2.61, π0.57; for CT4, π=0.92.
Model for the Lattice Dynamics of Metals and Its Application to Sodium
Authors: Sharma P. K. , Joshi S. K.
Published: January 2005

A simple lattice dynamical model for metals is presented. A body-centered cubic lattice of ion cores interacting with nearest and next-nearest neighbors imbedded in a uniform background of electron gas is considered. A secular equation determining the frequencies of normal modes of vibration is derived. This equation contains three force constants which can be written in terms of elastic constants. The dispersion relations are presented for propagation vectors in the [100], [110], and [111] directions. Comparison is made in the case of sodium with the experimental curves obtained from neutron spectrometry and also with theoretical calculations of Toya. Our model is found to give a satisfactory description of the lattice dynamics of sodium.
On Induced Transitions and Line Shifts in the Rotation—Vibration Spectra of Pressurized Diatomic Gases
Authors: Sharma Ramesh D. , Turrell George C.
Published: January 2005

A simple model is developed for a collision pair consisting of a polar diatomic molecule and a perturbing inert gas atom. The effects of long-range forces arising from the dipole and quadrupole moments of the polar molecule on its rotation—vibration spectrum are considered. Detailed calculations are carried out to obtain the integrated intensities of the induced Q branches and the rotational line shifts in the spectra of HCl— and HBr—inert gas mixtures. The calculated results for both phenomena agree in magnitude with the experimental data without the use of adjustable parameters. The results are also consistent with the observed temperature dependences of the Q-branch intensities. In its present form the theory is unable to reproduce quantitatively either the fine structure of the Q branch or the J dependence of the line shifts.
Photoinduced Change of Organic Free Radicals as Studied by ESR. I. Conversion of Allyl-Type to Alkyl-Type Radicals in Irradiated Polyethylene
Authors: Ohnishi Shun-ichi , Sugimoto Shun-ichi , Nitta Isamu
Published: January 2005

The allyl-type radical –CH2–ĊH–CH=CH–CH2– in irradiated polyethylene was converted into the alkyl-type radical –CH2–ĊH–CH2– upon uv illumination (λ 2537 Å). During the conversion total concentration of the radicals remained constant. The production curve of the alkyl-type radical reached a saturation at 43% conversion. Initial rate of production of the alkyl-type radical was found proportional to the light intensity, while the saturation concentration was the same for illuminations of different intensities. The initial rate was independent of the illumination temperature and of presence of added hydrogen gas. A reaction mechanism which involves an intramolecular hydrogen atom shift was put forward: –CH2–CH2–ĊH–CH=CH–⇌ lim k2k1–CH2–ĊH–CH2–CH=CH–.The corresponding kinetic equation was solved and the rate constants k1 and k2 as well as the quantum yield were calculated from experimental results. It was found that this mechanism would explain all the features of the reaction satisfactorily. In addition to conversion to the alkyl-type radical, minor reaction of the allyl-type radical also took place simultaneously to produce polyenyl radicals of shorter length, evolving hydrogen gas. These ESR results were consistent with the evidences obtained from uv—visible spectra.
Optimized Single-Configuration Wavefunction for the Ground State of Lithium Fluoride
Authors: McLean A. D.
Published: January 2005

A single-configuration self-consistent-field molecular orbital wavefunction for the 1Σ ground state of lithium fluoride from which a total molecular energy of —106.9885 a.u. at an internuclear separation of 2.8877 a.u. can be calculated is reported. It is shown on the basis of correlation energy arguments that this energy is within 0.007 a.u. of the Hartree—Fock energy for the ground state of this molecule. Results computed with wavefunctions of slightly lower accuracy (—106.9769 a.u. at the minimum in the computed potential energy curve) are reported over a range of internuclear separations from 1.6 to 4.85 a.u. The systematic approach used in obtaining the best wavefunction is described, since it appears to be a reasonable approach from the point of view of minimizing the amount of calculation involved, and for molecular wavefunctions this is a crucial consideration. A comprehensive table of expectation values including the dipole moment, kinetic energy T, potential energy V, ∑ irLi,i2,   ∑ i1/rLi,i,   ∑ i1/rF,i,   ∑ 1<j1/rij,and ∑ i(3zLi,i2−rLi,i2) computed with wavefunctions of varying degrees of approximation is given.
Nature of the Hydrogen Bond in Sodium Acid Fluoride
Authors: McGaw Barbara L. , Ibers James A.
Published: January 2005

Neutron diffraction data, obtained from single crystals of NaHF2 and NaDF2, have been analyzed in terms of several models for the bifluoride ion geometry. In sodium acid fluoride the bifluoride ion must be linear and the two fluorine atoms equivalent. The F–H–F distance is 2.264±0.003 Å, the F—D—F distance is 2.265±0.007 Å. From the diffraction data alone it is impossible to distinguish between a symmetric model for the bifluoride ion and one in which the potential for the hydrogen (or deuterium) along the bond has two equal minima on either side of the center. However from a comparison between the differences of mean-square amplitudes of vibration of hydrogen (or deuterium) and fluorine as obtained from the analysis of the diffraction data and as calculated from the spectroscopic frequencies it is concluded that the bifluoride ion is indeed symmetric.
Nuclear Magnetic Relaxation and Diffusion in Liquid SF6
Authors: Hackleman William R. , Hubbard Paul S.
Published: January 2005

The longitudinal nuclear magnetic relaxation time T1 and the diffusion coefficient D in a sample of SF6 liquified under pressure have been measured by spin—echo techniques. The closed sample contained approximately a critical density of SF6. The measurements were made at temperatures between the freezing temperature, 221°K, and 315°K, which is 3.5°K below the critical temperature. Misch metal was used as an oxygen getter in the preparation of the sample. The measured values of T1 are compared with values calculated on the assumption that the relaxation is due to spin—rotational interactions and to intra- and intermolecular dipole—dipole interactions. The calculated and measured values of (1/T1) agree fairly well if reasonable values of the spin—rotational interaction constants are assumed. The calculation indicates that the nuclear magnetic relaxation of liquid SF6 is produced mainly by spin—rotational interactions.
Vibrational Relaxation in High-Density Methane
Authors: Madigosky Walter M.
Published: January 2005

Ultrasonic absorption measurements were made in high-density methane over a range of densities from 400 to 560 amagats at —25°C and from —30° to 30°C at 400 amagats. The absorption may be accounted for by a single relaxation time and specific heat including at least the two lowest modes. Application of the modified cell model of Madigosky and Litovitz correctly predicts the density dependence and gives a collision diameter of 3.45 Å. The temperature dependence of the transition probability per collision agrees with that found by Eucken and Aybar and is compared with the Schwartz, Slawsky, Herzfeld theory. All results are interpreted as supporting the concept that only binary collisions were responsible for the energy-transfer process.
Electrical Conductivity of Potassium Films on Potassium Chloride
Authors: Wei Ling Y.
Published: January 2005

Potassium was evaporated onto a KCl crystal at 77°K under a vacuum of 10—9 Torr. Conductivity measurements were made before and after the film was annealed at room temperature. For the stable film, Ohm's law is obeyed up to about 25 V/cm and the temperature dependence of the conductance follows G=G0exp(—ΦE/kT) with ΦE=0.05–0.063 eV. The preannealed film became very unstable in a field near 250 V/cm and the current—voltage relation is nonlinear. The experimental results strongly suggest that in the stable film, the conduction is by the mechanism of impurity conduction subject to the Schottky effect while in the unsettled film, the currents, though mainly carried by electrons, are decisively controlled by mobile ions.
Removal of Orbital Degeneracy in an Asymmetric Molecular Environment
Authors: Brith M. , Schnepp O.
Published: January 2005

The absorption spectra of metal atoms in solid rare-gas matrices have recently been described. These spectra give evidence of the removal of the orbital degeneracy of P states of the trapped atoms. An investigation is made of the covalent and the dispersion interactions between the impurity atom and the host lattice and the contributions of these interactions to the splitting energy of the atomic excited P state of magnesium in a distorted lattice site in solid argon. It is concluded that the experimentally observed multiplet structure can be explained on the basis of physically reasonable models of asymmetric impurity sites. In particular, an impurity site with more than one adjacent vacancy is the most physically reasonable configuration.
Mass-Spectrometric Investigation of the Oxidation of Molybdenum and Tungsten
Authors: Berkowitz-Mattuck Joan B. , Büchler Alfred , Engelke John L. , Goldstein Steven N.
Published: January 2005

The oxidation of molybdenum and tungsten was investigated mass spectrometrically at temperatures between 1500° and 2600°K and oxygen pressures between 10—4 and 10—2 Torr. The principal products of oxidation were found to be the gaseous dioxide and trioxide, MO2(g) and MO3(g) (M=Mo or W). The trioxide is the more important species at low temperatures; the dioxide is the dominant product at high temperatures. Small amounts of polymeric oxides, (MO3)2(g) and (MO3)3(g) were formed at the lowest temperatures and highest oxygen pressures. The gaseous oxidation products are not in equilibrium with a solid surface oxide.
Carbon 2pz Multiple-Center Dipolar Interaction Integrals in the Matrix Element over LCAO Molecular Orbitals
Authors: Chiu Ying-Nan
Published: January 2005

A method has been devised to enumerate, according to magnitude, all significant multiple-center integrals that occur in the LCAO expansion of a matrix element belonging to the dipolar interaction operator over products of molecular orbitals. The coefficient, which consists of a product of atomic vector (expansion) coefficients, pertaining to each multiple-center integral was evaluated by an IBM 7090 FORTRAN program derived from the same logical principles as the above enumeration. The multiple-center dipolar interaction integrals were computed by (1) the Mulliken—Hameka approximation and (2) the Gaussian wavefunction method. Results from both methods for the integrals of naphthalene are compared. Results for two-center integrals using the Gaussian wavefunction method for a series of interatomic distances up to R=18.413 Bohr radii are also given.
Measurement of Infrared Band Contours in Solution
Authors: Abramowitz Stanley , Bauman Robert P.
Published: January 2005

Infrared band contours have been observed for nonpolar molecules in the liquid phase and in solution in nonpolar solvents with a spectral slitwidth of about 1 cm—1. A criterion was established for measuring the relative amounts of Lorentzian and Gaussian character to a band. It was found that symmetric bands were Lorentzian and that asymmetry appeared as a consequence of intramolecular effects that could be shown to be present in the vapor-phase spectrum.
Millimeter Wave Spectroscopy of Unstable Molecular Species. I. Carbon Monosulfide
Authors: Kewley Roger , Sastry K. V. L. N. , Winnewisser Manfred , Gordy Walter
Published: January 2005

The carbon monosulfide species CS32 and CS34 are investigated with a millimeter wave spectrometer designed for the study of short-lived molecules in the frequency range from 60 000 to 300 000 Mc/sec. Spectroscopic constants obtained are:           CS32          CS34B0=24 495.592±0.006 Mc/secB0=24 103.554±0.006 Mc/secBe=24 584.367±0.006 Mc/secDe=0.03979±0.0017 Mc/secαe=117.550±0.012 Mc/secHe=0.0625±0.009 kc/secDe=0.04285±0.00166 Mc/secHe=0.0653±0.0085 kc/secThe spectrometer is described. Its sensitivity has been estimated to be the order of 10—5 to 10—6 cm—1.
Electron Spin Resonance Studies of Irradiated Glasses Containing Boron
Authors: Lee Sook , Bray P. J.
Published: January 2005

Electron spin resonance (ESR) spectra have been observed for various types of alkali borate and borosilicate glasses which were exposed to γ-ray or thermal neutron irradiations. The irradiated alkali borate glasses (Li2O–B2O3, Na2O–B2O3, K2O–B2O3, Rb2O–B2O3, and Cs2O–B2O3) containing less than 25 mole % alkali oxide exhibit spectra consisting of five peaks in the resonance absorption curve at an operating microwave frequency in the vicinity of 9.2 kMc/sec. The same five-line resonance has also been observed in the irradiated borosilicate glasses (Corning 7070, 7740, and 7720). Investigations of the irradiated glasses by means of a K-band ESR spectrometer operating at approximately 23.3 kMc/sec have yielded spectra which are partially resolved into six lines. Alkali borate glasses isotopically enriched with B10 display a 10-line resonance at the X-band frequency when irradiated with γ rays or neutrons. It is concluded that the five- and six-line resonances arise from an axially symmetric hyperfine interaction of a hole with a B11 nucleus, while the 10-line structure arises from such a hyperfine interaction with a B10 nucleus. The atom containing this B11 or B10 nucleus is believed to be in a BO4 tetrahedral configuration in the glass structure.
Elastic Constants of Ammonium Chloride near the Lambda Point
Authors: Garland Carl W. , Jones Joseph S.
Published: January 2005

The adiabatic elastic constants of single-crystal ammonium chloride have been measured as functions of sound frequency from 5 to 55 Mc/sec, and as functions of temperature from ∼150° to 300°K by an ultrasonic pulse technique. The values of the constants at 300°K are c11 = 3.70, c44 = 0.86, (c11—c12)/2 = 1.41 in units of 1011 dyn cm—2. Special emphasis was given to the region around 243°K, the critical temperature for the order—disorder transition. The results are discussed in terms of the phenomenological thermodynamic theory of Pippard.
Infrared Spectra of the Germyl Halides
Authors: Freeman D. E. , Rhee K. H. , Wilson M. K.
Published: January 2005

The infrared spectra of GeH3F, GeH3Cl, GeH3Br, GeH3I, and their fully deuterated analogs have been measured. All the fundamental vibrations have been observed and assigned. Normal coordinate treatments based on both simple valence and Urey—Bradley force fields have been performed. For germyl fluoride, unusually large frequency shifts have been observed to accompany the phase transition from gas to solid.
Approximate Expression for the Tunneling Correction
Authors: Shin H.
Published: January 2005

By using an approximate method, the tunneling-correction factor for the unsymmetrical Eckart potential function and its temperature dependence are formulated in forms which are capable of simple numerical calculations. The method is designed to evaluate the integral which includes a violently changing exponent. The result is compared with Johnston's results obtained by electronic computation; the agreement is good in chemically interesting cases.
Normal Vibrations, Potential Constants, and Vibration—Rotation Interaction Constants in Cyclobutane and Cyclobutane-d8
Authors: Lord R. C. , Nakagawa I.
Published: January 2005

From the fundamental frequencies of cyclobutane and cyclobutane-d8 as observed in infrared and Raman spectra, the potential constants and eigenvectors of the normal vibrations have been calculated for an assumed structure of D4h symmetry. When the available frequencies were too few in number to evaluate the constants of a given species in the general D4h potential system, appropriate nondiagonal constants were set equal to zero. From the potential constants the zeta constants of vibration—rotation interaction were computed for D4h species Eg and Eu. The Eg constants were found to be correct in magnitude but of opposite sign to the zetas suggested by the infrared band contours. The sign change is that to be expected if the actual structure is D2d (puckered ring), as was shown by Mills and Duncan for the D2d structure of allene. The zeta constants and frequencies were therefore recalculated for species E of D2d. The calculated zetas agree well with the values expected from the band contours, and explain the unusual shapes of the bands at 749 cm—1 in cyclobutane and 556 cm—1 in cyclobutane-d8.
Vibronic Interactions in the Exciton Theory for Molecular Crystals
Authors: McRae E. G.
Published: January 2005

The correlation between exciton motion and intramolecular vibrational motions in the electronically excited states of molecular crystals is described in terms of a zone of molecular distortion surrounding the instantaneous site of electronic excitation. It is shown for a model crystal that observable properties of fluorescence spectra and of absorption spectra near the band edge can be related exactly to the distortion zone structure.

An equation governing the distortion zone structure is derived by a variational method in which the exciton energy is minimized with respect to the simultaneous variation of a set of parameters representing the distortion of each molecule in the crystal. It is shown that this equation can be solved by a convergent iterative procedure, regardless of the strength of intermolecular interaction.

An illustrative application to a linear crystal is described. Where appropriate, the theoretical results are compared with those of perturbation theory.
Kinetic Theory of Hot-Atom Reactions. II. Evaluation of Collisional Energy Loss. Application to Reactive Mixtures
Authors: Wolfgang Richard
Published: January 2005

The kinetic theory of reactions of atoms of high translational energy undergoing moderating collisions is further developed. The nature and validity of the assumptions underlying the treatment and the range of applicability of the final expressions are discussed in detail. It is shown that experimental data on the total probability of reaction in which the hot atom is chemically bound can be used to evaluate two fundamental quantities: (1) the reactivity integral, or reaction probability integrated over energy on a logarithmic scale (I) ; (2) a measure of average energy transfer in collisions of hot atoms with the reactive species (α).

The present treatment involves no variable or arbitrary parameters. As a result sufficient data may be obtained to provide stringent internal consistency tests of the applicability of the model and its assumptions to any given system.

Two types of systems are specifically treated: (1) a single reactant moderated by inert gas; (2) competitive reactions in systems of two reactants. The relative utility of such systems for determination of the basic parameters α and I is discussed. Examples of the use of the expressions developed to calculate average logarithmic collisional energy loss (α) are given. Recent data of Colebourne on interaction of hot F with CF4, and data of Root and Rowland on hot H in mixtures of D2 and CH4 are used. The α's derived indicate that moderating collisions in these media are highly inelastic. Root and Rowland's hypothesis that CH4 is a better moderator than D2 is quantitatively confirmed. The implications of these findings for the mechanism of hot-atom processes are briefly discussed.
Time-Dependent Variation-Perturbation Method for Many-Electron Systems
Authors: Karplus M. , Kolker H. J.
Published: January 2005

The variation-perturbation method for time-dependent problems is applied to many-electron systems. Specific formulas are developed for the steady-state dipolar interaction between an oscillating electric field and an atom or molecule whose wavefunction is approximated by a Hartree—Fock determinant. The method is illustrated by a number of calculations for the helium atom. Theoretical expressions for the dynamic polarizability, refractive index, and Verdet constant (Faraday effect) are obtained. Comparison with the available measurements shows good agreement between the experimental and the theoretical values.
Entropy of Fusion of Molecular Complexes
Authors: Rastogi R. P. , Nigam R. K. , Sharma R. N. , Girdhar H. L.
Published: January 2005

Heats of fusion of p-nitrotoluene, p-toluidine, benzophenone, diphenylamine, 1:1 benzophenone—diphenylamine complex, and 1:2 urea—phenol complex have been determined with the help of a thermistor calorimeter.
Pure Quadrupole Resonance Spectra of Trialkylboranes
Authors: Love Peter
Published: January 2005

The boron-11 quadrupole coupling constants of the simple aliphatic symmetrical trialkylboranes determined at 77°K are primarily a function of the number of α-carbon—hydrogen bonds in these compounds. The average value of e2Qqzz in triethyl, tri-n-propyl, and tri-n-butylborane is 125±4 kc/sec higher than that in trimethylborane. The quadrupole coupling constant in tri-isopropylborane is increased an additional 249±4 kc/sec above the value in the α-methylene compounds. The α-secondary hydrogen isotope effect in trimethylborane is to increase e2Qqzz by 28±4 kc/sec. However, there is no β-secondary hydrogen isotope effect in tri-isopropylborane within the limits of experimental error. These results, the proton high resolution NMR spectra, and the available chemical measures of the Lewis acidity of these compounds, are in excellent agreement with classical carbon—hydrogen bond delocalization theory.
NMR Studies of Phase Transitions. I. NaSH
Authors: Coogan C. K. , Belford Geneva G. , Gutowsky H. S.
Published: January 2005

NaSH is one of a group of compounds M+(QR)— whose high-temperature crystalline form might be called pseudo-NaCl cubic, but which crystallize in less symmetrical lattices at low temperatures. Two models have been proposed to account for the obviously linear ion QR— replacing a spherical ion in the cubic phase. Pauling suggested that the QR— ion tumbles rapidly and randomly enough to have an effective spherical form to the surrounding ions. Frenkel suggested that the QR— ions are static and point along one of the eight cube body diagonals (〈111〉 directions) at random so as to give long-range cubic symmetry. Previous attempts, based on x-ray diffraction experiments, to decide between these models have been unsuccessful. We have studied the H1 and Na23 nuclear magnetic resonances in polycrystalline samples of NaSH at temperatures between —65° and 200°C. Linewidth changes at 70°C and above reveal a 10° region of transition from the rhombohedral to the cubic phase. In this transition region, diffusion of the Na+ ions causes major narrowing of the Na23 resonance and partial narrowing of the H1. The narrowing of the proton resonance is continued at temperatures above 110°C by diffusion of the SH— ions.

The second moment of the proton absorption observed at ∼90°C, when compared with values calculated for several models, is consistent with rapid, random reorientations of the SH— ion among the eight 〈111〉 directions in the cubic phase. Similar calculations and comparisons provide evidence that the SH— ion reorients also in the rhombehodral phase. Here, however, the stable orientations appear to be in the six pseudo-〈110〉 directions perpendicular to the trigonal axis. Thus, the phase transition is a cooperative process resulting from the increasing population, at higher temperatures, of the pseudo-〈111〉 directions in the rhombohedral phase.

The Na23 resonance is observed in the rhombohedral phase, even though the Na23 quadrupole splitting is generally large enough in noncubic crystals to obliterate the NMR absorption in powders. Electric-field gradient calculations, assuming point charges, indicate that the Na23 quadrupole splitting can be negligible in the dynamic structure we propose.
Paramagnetic Resonance Measurements of the Phosphorescent State of Quinoxaline
Authors: Vincent James S. , Maki August H.
Published: January 2005

Paramagnetic resonance absorption has been observed in a single-crystal solid solution of quinoxaline in durene when irradiated at 77°K with uv light from an AH-6 mercury-arc source. The fine structure of the resonance spectrum observed at 9.8 Gc/sec may be described by the spin Hamiltonian H=BH·g·S+DSz2+E(Sx2−Sy2),in which S = 1. D/hc=±0.1007±0.0003 cm−1E/hc=∓0.0182±0.0002 cm−1  gxx=2.0047±0.0005  gyy=2.0035±0.0005gzz=2.0019±0.0005.The fine structure is practically identical to that of the naphthalene triplet state observed by Hutchison and Mangum.

The observed hyperfine structure is assigned to a coupling with the 5, 8 protons, and the two N14 nuclei. The angular dependence is in qualitative agreement with the tensor for C–H proton hyperfine interaction for doublet-state aromatic radicals measured by Cole, Heller, and McConnell, as well as the tensor for aromatic N14 interaction derived from experiments by Weissman. With the assumption that hyperfine interaction in a triplet state may be described by the same tensors, normalized π-electron spin densities are approximately 0.28 for the 5, 8 carbon atoms, and 0.1 for the N14 atoms. Satellite lines which are split from the primary hyperfine lines by the proton resonance frequency are observed and interpreted as simultaneous electron-spin nuclear-spin transitions. The interactions leading to these transitions are assumed to be primarily due to hyperfine coupling with protons whose unresolved first-order interaction is much smaller than the proton-resonance frequency.
Structure and Rotational Isomerization of Free Hydrocarbon Chains
Authors: Bartell L. S. , Kohl D. A.
Published: January 2005

An electron diffraction investigation has been carried out for the molecules n-butane, n-pentane, n-hexane, and n-heptane in the gaseous phase. Mean bond lengths and bond angles were reported in earlier papers. The present paper is concerned with information derivable from the observed spectrum of nonbonded distances. A scheme is presented for determining both trans and gauche bond angles despite the fact that the 2.5-Å nonbonded C···C trans and gauche radial distribution peaks are too badly overlapped to be resolved. Formulas are given for calculating torsional ``shrinkage effect'' corrections for nonbonded distances.

It was found that a given gauche conformation has a higher free energy than its corresponding trans counterpart by about 610 cal/mole. If the source of this free-energy difference is steric, arising from repulsions between hydrogens on gauche carbons, there should be structural as well as thermodynamic manifestations. The positions of a total of 21 independent nonbonded C···C radial distribution peaks were interpreted in terms of a model of steric deformations in gauche structures. The results, including estimates of standard errors, were φ(gauche)=61.0±3° dihedral angle, α(trans)=112.65±0.3° C–C–C angle, α(gauche)—α(trans)=0.1°±1°, and the distortion from planarity of trans conformations adjacent to gauche was η=7±4°. The C–C bond length and C–C–C bond angle, averaged over all conformations, were 1.5328±0.002 Å and 112.71±0.15°, respectively.