bluuebunny/crossref_metadata_2025 huggingface dataset:
Kinetics of Unimolecular Decomposition of Excited Alkylamine Ions
Authors: Chupka William A. , Berkowitz Joseph
Published: January 2005

The unimolecular reaction RCH2NH2+→R+CH2NH2+ has been studied for the n-alkylamines from ethyl- to n-heptylamine inclusive by a mass spectrometric technique. The intensity of the metastable ion produced in the above reaction was measured and used to determine the variation of the specific rate constant with the internal energy of the molecular ion. The results are compared with those predicted by various theories. The agreement of the data with the theories of Kassel and of Rosenstock is bad for the smallest molecules but improves with increasing number of oscillators in the molecule. Earlier evidence for intramolecular vibrational relaxation in the parent molecular ions is discussed in relation to the assumptions of Slater's theory. A simplified application of Slater's theory seems unable to explain all the data.
Potential Energy Constants, Rotational Distortion Constants, and Thermodynamic Properties of H2C=C=O and D2C=C=O
Authors: Sundaram S. , Cleveland Forrest F.
Published: January 2005

As a check on the assignments of the fundamentals of ketene (H2C=C=O), a normal coordinate analysis has been carried out and the constants for the general quadratic potential energy function for this molecule have been obtained. Using these constants, the fundamental vibrational wave numbers for the deuteroketene have been calculated, and compared with the observed bands reported for this molecule. The moments of inertia tensor derivatives for the general X2YXW molecule have been obtained. The rotational distortion constants for H2C=C=O and D2C=C=O have been determined. The molar thermodynamic properties—heat content, free energy, entropy, and heat capacity—have been calculated for both molecules for various temperatures from 100° to 1000°K at atmospheric pressure for the rigid-rotor, harmonic-oscillator approximation.
Enrichment of Nitrogen-15 by Chemical Exchange of NO with Liquid N2O3
Authors: Monse E. U. , Spindel W. , Kauder Lois Nash , Taylor T. I.
Published: January 2005

The characteristics of the two-phase exchange system: N214O3(liq)+N15O(gas)⇄N14N15 O3(liq)+N14O(gas) have been studied in laboratory exchange columns to evaluate its usefulness for concentrating nitrogen-15. The effective single stage separation factor α has been determined both by direct equilibration of liquid and gas phases, and by measuring the over-all separation in an exchange column as a function of the rate of product with-drawal. The factor α varies from 1.035±0.005 at —14°C to 1.016±0.004 at +14°C. The system is complicated by the presence of additional oxides of nitrogen in both phases, and it is not yet possible to evaluate the contributions of each of the individual molecular species to the effective separation factor. The over-all separations achieved at total reflux in a 40-stage bubble plate column corresponded to a maximum plate efficiency of ∼60% at an interstage flow of ∼50 mM N/min cm2. Similarly, the separations obtained in a 95-cm column packed with stainless steel wire helices corresponded to stage heights of 1.1 and 1.2 cm for interstage flows of 23 and 31 mM N/min cm2, respectively. A comparison of the present system with the nitric acid-nitric oxide exchange system indicates that approximately equal volumes of column would be required for the same isotope separation task in spite of a considerably lower α for the N2O3 system. This is due to the higher rate of exchange as evidenced by lower stage height. The favorable stage height for this process makes it possible to prepare highly concentrated nitrogen-15 in shorter columns than those used for the nitric acid exchange.
Thermodynamic Inequalities for Elastic Solids
Authors: Li James C. M. , Kiang Hsiao S.
Published: January 2005

A table of all the positive quantities among measurable coefficients is given for anisotropic elastic solids under the variation of only temperature and stress. Examples of inequality formulation are presented. Upper or lower limits containing only the Grüneisen's parameter and heat capacities are derived for adiabatic and isothermal compressibilities, thermal expansion, and thermal stress.
Theory of Electronic Excitation and Reorganization in the Formaldehyde Molecule
Authors: Parks Joe M. , Parr Robert G.
Published: January 2005

The use of a previously described iterative method of separated electron pairs is demonstrated by calculations on the formaldehyde molecule. Investigation is made, for example, of detailed changes in the polarity of sigma bonding electron wave functions in this molecule when a pi or lone-pair electron is excited or ionized. The molecule is treated as a six-electron problem (four electrons in the C=O bond plus two lone-pair electrons on O); matrix elements involving the ``core'' are obtained by fitting experimental data. The use of Pariser-type one-center repulsion integrals is tested in conjunction with various sets of two-center repulsion integrals. Although one combination gives reasonable results, none of the combinations is found to be entirely satisfactory, and a procedure is outlined from which could be obtained one-center integrals approximately incorporating Arai-Hurley type corrections. It is demonstrated (with reservations) that the constant sigma structure assumption, usually made in calculations of pi electron excitations and ionizations, is not always good with regard to wave functions, but that it may lead to only small errors in calculated energies.
Photolysis of Ammonia in a Solid Matrix at Low Temperatures
Authors: Schnepp O. , Dressler K.
Published: January 2005

Solid deposits of argon containing 0.3 mole % ammonia were irradiated at 4.2°K with light of wavelengths shorter than 2000 A. The emission of a hydrogen discharge with a LiF window and of a thin-walled quartz mercury arc were used. The production of the unstable species NH and NH2 was observed by means of electronic absorption spectroscopy. Experiments using filters led to the conclusion that NH is produced by irradiation with light of wavelengths shorter than 1550 A. NH2 is produced by radiation above 1700 A and below 1550 A with comparable quantum efficiency. Warmup experiments show that NH2 disappears close to 20°K whereas NH is stable up to at least 36°K. Photolysis at 20°K is approximately five times less efficient than at 4.2°K. On certain assumptions a molar absorption coefficient of 40 000 is estimated for both NH and NH2 and the f values of the observed transitions of these molecules are estimated to be of the order of 10—3.
Inter- and Intramolecular Potentials and the Spectrum of Ice
Authors: Haas C. , Hornig D. F.
Published: January 2005

Whereas the spectra of H2O and D2O ice cannot yet be explained unambiguously, the spectra of HDO in dilute solution in either H2O or D2O may be interpreted readily. In particular, since vOH occurs at 3275 cm—1 and 2 vOH at 6300 cm—1, nearly the harmonic value, the barrier to proton transfer lies well above the latter level and must exceed 23 kcal/mole. The width of vOD at 2416 cm—1 is only 20 cm—1, whereas that of vOH is about 80 cm—1 and 2 vOH about 600 cm—1. These widths can be explained by proton tunneling if the barrier height is near 32 kcal, in which case the second minimum must lie below the level vOH. It must therefore be less than 14 kcal/mole above the primary minimum. A doubling of vOD from OD···OD pairs was also observed and the magnitude of the splitting is consistent with an effective charge of 0.6e on the protons. It is clear from these results that the usual width of hydrogen bonded OH lines is not an intrinsic characteristic of the O–H···O bond but results largely from intramolecular coupling of the O–H motions.
Approximate Isotopic Frequency Rule and Its Application to the Spectra of Complex Molecules
Authors: Krimm S.
Published: January 2005

An isotopic frequency rule is derived which is valid to a good approximation for individual modes of fully substituted hydrogen-containing groups in a complex molecule. It is given by λi/λ = 1 — (ΣjΔTj/ρT), where λ = 4π2ν2, ρ = mi/m = ratio of the isotopic to the normal mass, T = total kinetic energy associated with the vibration, and ΣjΔTj = differential kinetic energy associated with the substituted atoms. When applied to H2O and NH3 this rule reproduces frequency ratios to better than 0.5%. The rule is used to predict the frequency ratios for the various modes of the CH2 group, and with illustrations from the infrared spectra of high polymers it is shown how this rule can be of assistance in making assignments and in providing information on the separability of group vibrations.
Pyroelectric Effect in the Cubic ZnS Structure
Authors: Landauer Rolf
Published: January 2005

The classical theory of pyroelectricity, which uses only the symmetry of the crystal class, is shown to be incorrect. The surface structure is also relevant. The case of cubic ZnS is discussed in detail.
Infrared Spectra of Alkyldiboranes. II. Monoethyldiboranes
Authors: Lehmann Walter J. , Wilson Charles O. , Shaprio I.
Published: January 2005

The infrared spectra of five isotopic variants of monoethyldiborane, C2H5B210H5, C2H5B2H5, C2H5B2D5, C2D5B2H5, and C2D5B2D5, are analyzed and frequency assignments are made. The frequencies and intensities of the various bands are compared with those in the corresponding monomethyldiboranes and the related terminally substituted B2H5D and B2D5H, as well as with triethylboranes. In addition, vapor-pressure data in the — 58° to — 110°C range for isotopically normal ethyldiborane are reported.
Effect of Chemical Etches on the Fast Germanium Surface States
Authors: Margoninski Y.
Published: January 2005

Simultaneous measurements of surface recombination velocity and added trapped charge density in the fast states as a function of surface potential were carried out on one and the same n-type filament which was subjected to three different etches: CP—4A, concentrated HNO3 and HF. Most measurements were performed at various temperatures. It was found that (a) the reproducibility of surface state parameters after successive treatments with CP—4A was excellent; (b) the influence of the different etches was surprisingly small, with one exception: the average capture probability cp for holes was found to undergo a more than threefold increase after treatment with HF; (c) the energy of the recombination center did not always decrease with increasing temperature, contrary to all previously reported measurements.
Isotope Effect in the Hydrogen Atom-Formaldehyde Reaction
Authors: McNesby James R. , Scheer Milton D. , Klein Ralph
Published: January 2005

The isotope effect in the hydrogen abstraction from formaldehyde by hydrogen atoms has been measured. The activation energy difference derived from relative rate measurements of the pair of reactionsH+H2CO→H2+HCOH+D2CO→HD+DCOis E5 — E2 = 1.0 kcal. The value for the corresponding pair D+H2CO→HD+HCOD+D2CO→D2+DCOE7 — E6 = 0.9 kcal, is calculated from (5), (2), and the variation of the hydrogen-deuterium equilibrium constant with temperature. Application of the Bigeleisen theory of the isotope effect to these reactions suggests a loosely bound activated complex.
Approximate Analytical Wave Functions for the 1sns 1S States of He and He-Like Ions
Authors: Ritter Z. , Pauncz R.
Published: January 2005

Calculations have been made for the 1s2s, 1s3s, and 1s4s 1S states of He and He-like ions, assuming wave functions of the symmetrized product form, u(1) v(2)+u(2) v(1). The results are the best obtained till now using such a functional form, and are even better than some recent calculations which, in addition, use angular correlations.

The energy values obtained for He are: 2.14307, 2.06036, and 2.03320 for the 1s2s, 1s3s, and 1s4s 1S states, respectively. The wave functions obtained were checked by other criteria besides the energy criterion.
Composition Limits of Stability of PbTe
Authors: Brebrick R. F. , Allgaier R. S.
Published: January 2005

Single crystals of PbTe have been heat-treated in evacuated silica tubes in the presence of Pb- or Te-rich ingots. At the heat-treatment temperatures, which ranged between 404° and 885°C, the ingot compositions were such that solid PbTe, liquid, and vapor phases coexisted. At a given temperature, the PbTe crystals were therefore as rich in Pb or Te as possible at equilibrium. After quenching the crystals, the resistivity and Hall constant were measured at room temperature and 77°K. Below about 860°C, crystals heated with Pb-rich ingots were n type. Those heated with Te-rich ingots were p type at all heat-treatment temperatures. The difference in the concentrations of electrons and holes at room temperature was taken as equal to the difference in concentration of lead and tellurium atoms at the heat-treatment temperature and was used to construct the PbTe solidus lines. The range of stability of PbTe is a maximum near 775°C and is between 49.994 and 50.013 at.% Te, corresponding to carrier concentrations of 3.3×1018 electron/cm3 and 7.6×1018 holes/cm3, respectively.
Nonstoichiometry and Ferroelectric Properties of PbNb2O6-Type Compounds
Authors: Subbarao E. C. , Shirane G.
Published: January 2005

The crystal structure of PbNb2O6 consists of a framework of NbO6 octahedra linked through corners. The Pb2+ ions occupy 5 out of the 6 available interstitial sites in this framework. Single-phase compositions have been prepared by solid-state reactions to yield nonstoichiometric compounds of the form A1+xB2O6 where A and B may consist of two ions of different valency and x has values between —0.08 and 0.15. In these materials, the number of unfilled interstitial sites inherently present in PbNb2O6 lattice has been varied. Lattice parameter and x-ray intensity data confirm that the additional ions introduced occupy the same sites as Pb2+ ions.

The ferroelectric Curie temperature has been studied as a function of the composition of these dielectric solids. For compositions with x>0, the Curie temperature is not very sensitive to composition. As the number of unfilled interstitial sites increases (x<0), the Curie temperature decreases sharply.
Anomalous Relaxation of Hyperfine Components in Electron Spin Resonance
Authors: Schreurs Jan W. H. , Blomgren George E. , Fraenkel George K.
Published: January 2005

It is shown that the different hyperfine components in the electron-resonance spectra of free radicals exhibiting proton hyperfine splitting saturate at different rates, and different sets of relaxation times must be used to describe the behavior of each component. The variations in the relaxation times (T1 and T2) were found to be approximately symmetric about the center of the spectrum, and the central component is the narrowest and saturates more readily than the outer components. A qualitative discussion is given of the relaxation and line-broadening mechanisms which may be responsible for the variations in T1 and T2. In solutions of the p-benzosemiquinone ion at room temperature, the values of T1 and T2 were found to be approximately 10—6 sec. An analysis is given of the experimental parameters which affect saturation measurements, including the effect of a nonuniform rf field in a rectangular cavity, and a study is made of the type of spectra to be expected when the individual hyperfine components have different values of T1 and T2. An appendix is included on the work of Jen et al. on deuterium atoms trapped at liquid helium temperature, which shows that the anomalous intensities obtained in these low-temperature experiments as a function of rf power is not the same as the phenomenon observed for free radicals in solution and cannot be adequately interpreted in terms of any currently proposed mechanisms.
Madelung Constants of the Cubic Perovskite Structures
Authors: Fumi F. G. , Tosi M. P.
Published: January 2005

A proof is given of a simple linear relation between the Madelung constant, referred to the lattice parameter a, of a cubic perovskite structure ABX3 with the ionic charges in the ratio +z:+(3—z):—1 and the corresponding Madelung constants for the NaCl, CsCl, and Cu2O structures.
Chemiluminescence of Ethylene Formed Probably from Methylene in an Inert Matrix
Authors: Goldfarb Theodore D. , Pimentel George C.
Published: January 2005

An orange-red luminescence occurs when diazomethane suspended in solid nitrogen or solid argon is photolyzed and then warmed to permit diffusion. Spectrographic and visual studies of this thermoluminescence are reported here. Conditions favorable for the production of the luminescence also result in relatively high yields of ethylene as a final product. Furthermore, a deuteration effect is observed. For CH2N2 the recorded spectrum consists of a distinct feature at 6030 A and an extremely weak feature near 6530 A. Deuterated diazomethane produces a spectrum with two distinct features at 6055 and 6405 A, and one or more weaker absorptions between 6700 and 6800 A. The emission is assigned to chemiluminescence of ethylene and a tentative interpretation is given in terms of two excited states of ethylene (Z→V).
Compression and Phase Transitions of Solid NH3, SiF4, H2S, and CF4
Authors: Stewart John W.
Published: January 2005

Isothermal PV curves of solid NH3, SiF4, H2S, and CF4 have been observed by the direct piston displacement method up to pressures of 20 000 kg/cm2 at various temperatures between 100° and 200°K. Relative volume changes and compressibilities are given for each substance except CF4. Phase transitions have been observed as discontinuities in the piston motion. NH3 exhibits no phase transitions. Phase diagrams are given for the other three substances. Comparison with previous work in the case of H2S shows only partial agreement. In some instances the approximate volume changes accompanying the phase transitions have been determined.
Theoretical Dielectric Behavior of an Ethyl Stearate-Heneicosane Mixture
Authors: Broadhurst Martin G.
Published: January 2005

The variation in potential energy with position for an ethyl stearate molecule rotating rigidly about its chain axis in a heneicosane lattice has been found by evaluating the potential energy of the component atoms at 18 angular positions of the molecule. The potential energy function considered involves attractive van der Waals terms in the inverse sixth, eighth, and tenth powers of the distance and an exponential repulsive term. The resulting potential energy curve was used to find possible molecular motions, and calculations of the predicted dielectric relaxation dispersion were made. The model predicts only two positions available to the ethyl stearate molecule and hence only one dielectric relaxation time. Exact calculations of the dielectric properties of a mixture of ethyl stearate in heneicosane were found to be difficult because of the extreme sensitivity of the results to slight errors in the assumed energy function.
Simple Configuration Interaction Wave Functions. III. Three-Electron Atomic System: An Analytic Study
Authors: Machacek Milos , Scherr Charles W.
Published: January 2005

An analytical study of the 2S ground state of lithium like ions employing Slater-type orbitals to form the open-shell function (1s1s′2s) and the angularly correlated configuration-interaction functions (1s1s′2s)+λ1s(2p)2 and (1s1s′2s)+λ2s(2p)2 has been made. Expressions for the wave function parameters and energy values in terms of the nuclear charge Z have been obtained. These are asymptotic expansions for large Z, but they reproduce numerically obtained results for small Z with sufficient accuracy to be useful for many purposes. An unusual result is that, for large Z, the computed energy values are lowest if the orbitals 1s and 1s′ are allowed to have complex orbital exponents.
Some Neglected Subcases of Predissociation in Diatomic Molecules
Authors: Mulliken R. S.
Published: January 2005

The theoretically to be expected effects of the Franck-Condon factor in predissociation in diatomic molecules are examined qualitatively for cases in which the potential-energy curve of the predissociating electronic state crosses that of the predissociated state at an internuclear distance rc near or less than the equilibrium distance re of the latter state. It is shown that the incidence of predissociation as a function of the vibrational and rotational quantum numbers v and J should be quite different in such cases than in the more familiar cases where rc>re. Various subcases of Herzberg's cases a, b, c depending on the relation of rc to re are specified and designated. Some probable examples of known predissociations where rc<re are discussed. The need for further quantitative studies is emphasized.
Antiferromagnetic Coupling and Covalent Bonding in Almost Totally Ionic Salts
Authors: Waite Thomas R.
Published: January 2005

Anderson has recently presented an analysis of antiferromagnetic coupling in salts. His results are derived and extended by an alternate, more physical method. The problem of antiferromagnetism in salts is the problem of spin-spin coupling between two magnetic cations separated by an intervening anion. A linear three-ion array (in the presence of the rest of the crystal) is considered from the viewpoint of molecular orbital theory. In anticipation of electron-electron correlation, and in order to associate each electron spin with only one cation, the molecular orbitals are relocalized. Configuration interaction is small and may be treated by perturbation theory. The perturbation matrix is defined in terms of this representation rather than as a real physical part of the Hamiltonian. The cation-cation spin coupling terms appear as isolated, additive perturbing terms. The expansion parameter is the percent covalent character of the anion-cation bond. Coupling is antiferromagnetic for cations with from five to eight d electrons. Parameters may be estimated from (1) crystal field splittings and/or (2) hyperfine interaction between magnetic electrons and anion nuclei. The perturbed ground state wave function is reduced to a single Slater determinate involving nonorthogonal one electron wave functions, thereby revealing the physical cause of the coupling. Since no cation-cation coupling occurs in zero order with localized orbitals, the spin functions can be constructed from eigenfunctions of the individual cation spin operators using Clebsch-Gordon series. The coupling energy is of the form KijSi·Sj where Si is the total vector spin of cation i in the zero-order representation.
Absorption Spectra of Solid Methane, Ammonia, and Ice in the Vacuum Ultraviolet
Authors: Dressler K. , Schnepp O.
Published: January 2005

The vacuum ultraviolet spectra of solid ammonia and ice are found to be shifted to higher frequencies relative to the corresponding vapor spectra by 7000 cm-1. The effects of hydrogen bonding in the ground states of these solids, and the nature of repulsive interactions possible in the excited states are discussed. In methane, which forms a pure van der Waals solid, the spectra of gas and solid are found to be very similar.
Perturbation of Molecular Rotation-Vibration Energy Levels by Rare Gases
Authors: Rank D. H. , Eastman D. P. , Birtley W. B. , Wiggins T. A.
Published: January 2005

The shift in frequency of lines of the 2–0 band of HCl and of the ν1+ν3 band of C2H2 due to the presence of krypton and xenon as foreign gases has been measured. A marked J dependence was observed. The relative shifts in the upper and lower states of the transitions were calculated from the shifts in the Δ2F″(J) and Δ2F′(J) values obtained from the measured line shifts. In the case of HCl the shifts in the rotational levels were markedly different in the upper and lower states, the upper state shift being proportional to J, while the lower-state energy-level shifts approach an asymptotic value for high J. For C2H2 the shifts in both levels resembled the shift in the lower state of HCl.
Nuclear Magnetic Resonance Spectrum of B11 in Inderite
Authors: Pennington K. S. , Petch H. E.
Published: January 2005

The quadrupolar splitting of the B11 nuclear magnetic resonance signal in a single crystal of inderite Mg2B6O11·15H2O at room temperature has been investigated in a magnetic field of 7187 gauss. The spectra obtained as the crystal was rotated in turn about three mutually perpendicular axes held normal to the magnetic field were interpreted on the basis that the six B11 sites per unit cell belong to three distinct types with the two sites of each type related by a center of symmetry. The electric quadrupole coupling constants Cz and asymmetry parameters η at the three unique B11 sites were determined to be Cz=eQφzz/h355±5 kc/sec517±7 kc/sec2546±10 kc/secη=(φxx−φyy)/φzz0.51±0.030.76±0.010.066±0.003It has been inferred from the foregoing values that two of the boron atoms in the asymmetric unit of inderite have tetrahedral coordinations whereas the third has triangular coordination. The orientations of the principal axes of the electric field gradient tensors at the B11 sites have also been determined.
Interaction of Condensable Gases with Cold Surfaces
Authors: Sears G. W. , Cahn J. W.
Published: January 2005

Deposition from a molecular beam onto a cold target surface only occurs when the beam pressure is many orders of magnitude larger than the vapor pressure of the depositing phase at the substrate temperature. The critical beam pressure for deposition has been interpreted as a critical supersaturation for heterogeneous nucleation of a condensed phase. It is shown that the critical beam pressure is much too large to be accounted for as a critical value for nucleation if the adsorbate temperature and the substrate temperature are alike. The interpretation of critical deposition phenomena as a nucleation event must include the additional assumption that the adsorbate temperature is somewhat higher than the substrate temperature.
Atomic and Molecular Hydrogen Yields from Irradiated Acids
Authors: Livingston Ralph , Weinberger A. J.
Published: January 2005

The paramagnetic-resonance method has been used to measure the yields of atomic hydrogen from many concentrations of aqueous sulfuric, phosphoric, and perchloric acids at 77°K after irradiation with gamma rays. The yields of molecular hydrogen (and oxygen) have also been measured after similarly irradiated acids were warmed and the gases collected. The correspondence between atom and molecule yields is discussed. In sulfuric and phosphoric acids the atom and molecule yields depend upon whether the acid is a glassy or crystalline solid at the time of irradiation. Prolonged irradiation of 0.129-mole-fraction sulfuric acid (glassy) gives a saturation concentration of 3.4×1018 hydrogen atoms per gram. The corresponding number for 0.125-mole-fraction perchloric acid is 2.9×1019. The scavenging effects of nitric acid and hydrogen peroxide on the atomic and molecular hydrogen yields for 0.129-mole-fraction sulfuric acid have been measured and are discussed. The corresponding effect of nitric acid on the atom yield from perchloric acid is presented.
Relative Quenching Cross Sections in the Reaction of Hg(63P1) Atoms with Isotopic N2O Molecules
Authors: Hoffman Morton Z. , Bernstein Richard B.
Published: January 2005

The N14/N15 and O16/O18 isotope effects in the Hg(63P1)-photosensitized decomposition of nitrous oxide have been measured. Observed isotopic fractionation factors, S0 (interpreted in terms of ratios of rate constants for quenching by N14N14O16 vs N15N14O16, N14N15O16, and N14N14O18), are related to the ratio of isotopic quenching cross sections by the equation Q/Q*=S0(μ/μ*)½, where μ and μ* are the collisional reduced masses for Hg and the light and heavy isotopic molecules, respectively. The quenching cross section ratio for N142O16/N142O18 was unity within the experimental uncertainty (±0.1%). The ratios for N14N14O16/N15N14O16 and N14N14O16/N14N15O16 differed from unity by +0.98 and +0.44%, respectively. The order of the quenching cross sections for the isotopic nitrous oxide molecules is thus: N15N14O16<N14N15O16<14N14O18≅N14N14O16. The implications of the present observations are briefly discussed.
Dielectric Relaxation of Isoamyl Bromide
Authors: Glarum Sivert H.
Published: January 2005

The complex dielectric constant of isoamyl bromide has been measured at 1, 3, and 9 kMc between —75° and 25°C. Complex plane plots indicate an asymmetric, skewed-arc distribution of relaxation times, with the shape of the distribution function not being appreciably temperature dependent. A defect diffusion model is proposed to explain the dielectric behavior of this system. This model implies that the relaxation of a molecule is more probable immediately after one of its neighbors has relaxed than at an arbitrary time. A distribution of relaxation times is derived which, under the appropriate conditions, closely resembles that of the empirical skewed-arc function.
Open First-Order Stochastic Processes
Authors: Gans Paul J.
Published: January 2005

The solution of the general open first-order stochastic process representing the relaxation of an open multistate system is obtained by the generalization of a method of Krieger and Gans. The result is valid for a system containing an arbitrary number of absorbing and semiabsorbing states as well as allowing the presence of any number of emitting states. The stability of the solution is discussed in terms of the matrix of the transition probabilities. This is done with the aid of a theorem of Lévy and Hadamard. The result is applied to the corresponding closed system as well as the present work.
Detection of Order in Ni3Co
Authors: Yao Y. L.
Published: January 2005

Measurements of the variation of oxidation rate of nickel-cobalt alloys with composition and of the variation of saturation magnetization and thermal emf of Ni3Co with temperature show that Ni3Co has a tendency to order at low temperatures. The critical temperature of ordering is shown to be 773±1°C.
Comments on Hypervelocity Wave Phenomena in Condensed Explosives
Authors: Chaiken R. F.
Published: January 2005

The occurrence of hypervelocity wave phenomena in condensed explosives during shock initiation to detonation is discussed in terms of an adiabatic reaction model for the chemical energy release (i.e., the detonation reaction). On the basis of the model, the chemical reaction exhibits an apparent induction time resulting in a sudden release of energy behind the initiating shock front. It is believed that this energy release leads to a propagated high-pressure reaction wave which moves in the shock compressed explosive at a ``super-velocity'' (i.e., greater than the normal steady-state velocity) to overtake the initiating shock front. The proposed explanation is consistent with the reported observations of hypervelocity wave phenomena in detonating liquid nitromethane and single crystals of PETN.
Separation of Boron Isotopes. IV. The Methyl Sulfide-BF3 System
Authors: Palko A. A. , Drury J. S.
Published: January 2005

The exchange of boron between BF3 (gas) and the dimethyl sulfide-BF3 complex (liq.) was studied from —20°C to +26°C. The single stage separation factor changed from 1.056 to 1.031 over this temperature range with B10 concentrating in the liquid phase. Vapor pressures of dimethyl sulfide and of various mixtures of BF3 and dimethyl sulfide were determined. ΔH for the reaction BF3 (gas)+Me2S (liq.)→BF3·Me2S (liq.) was estimated to be —10.1 kcal/mole over the above temperature range. The melting point of the 1:1 complex was —19.6°C.
Quantum Mechanical (Phase Shift) Analysis of Differential Elastic Scattering of Molecular Beams
Authors: Bernstein Richard B.
Published: January 2005

For a spherically symmetrical intermolecular potential V(r)=εf(r/σ) the quantum calculation of the elastic scattering cross section dσ(Θ)/dΩ in the c.m. system is carried out as follows. For a given relative velocity (or deBroglie wavelength) and an assumed V(r), the radial wave equation is integrated for successive values of the angular momentum quantum number l, yielding the phase shifts ηι. Then dσ(Θ)dΩ is computed in terms of the series of ηι's in the standard way. A general computational program (following that of K. Smith) is outlined for the evaluation of the radial wave function and the phase shifts, utilizing an IBM 704 computer. Calculations are presented for the L-J (12, 6) potential function. The results may be concisely represented using the framework provided by the semiclassical treatment of Ford and Wheeler, i.e., in terms of a set of reduced phase constants vs reduced angular momenta at various reduced relative kinetic energies K. Tables and graphs are presented from which the phases may be obtained, to a good approximation, for any given ε, σ and K. Computation of the differential and total cross sections from the phase shifts is then readily accomplished.

The results are compared with the classical and semiclassical treatments. The problem of tunneling and orbiting is discussed.
Separation of Gas Mixtures in a Supersonic Jet. II. Behavior of Helium-Argon Mixtures and Evidence of Shock Separation
Authors: Stern S. Alexander , Waterman P. C. , Sinclair T. F.
Published: January 2005

Further experimental evidence is presented for the separation of gas mixtures in the supersonic jet formed by a Laval nozzle. The results are in agreement with a separation theory based on free-molecule kinetics. In addition, anomalies are observed which can be attributed to pressure diffusion effects generated during passage through an oblique shock front located at the exit plane of the nozzle.
Thermal Expansion of Delta and Epsilon Zirconium Hydrides
Authors: Kempter Charles P. , Elliott Reed O. , Gschneidner Karl A.
Published: January 2005

The thermal expansion characteristics of polycrystalline delta (face-centered-cubic) zirconium hydride and epsilon (body-centered-tetragonal) zirconium hydride were determined between room temperature and 362°C and 300°C, respectively, by means of x-ray diffraction techniques. The average linear thermal expansion coefficient for the delta phase is 2.98×10—6/°C for the range 24° to 362°C. For the epsilon phase, the average coefficients for the range 24° to 300°C are —1.4×10—6/°C and 30.6×10—6/°C for the a and c directions, respectively, and 9.3×10—6/°C for the randomly oriented polycrystalline material.
Some Intra-Atomic Correlation Correction Studies
Authors: Krauss M. , Ransil B. J.
Published: January 2005

The applicability of the ``intra-atomic correlation correction'' (ICC) formulation of Hurley is discussed. It is shown that accurate bond energies cannot be obtained with the usual restricted basis set without employing another empirical procedure, although it may be possible to obtain accurate excitation energies.
Organic Semiconductors. II. The Electrical Resistivity of Organic Molecular Complexes
Authors: Labes Mortimer M. , Sehr Robert , Bose Monisha
Published: January 2005

Thirty molecular complexes involving quinones, halogens, polynitroaromatics, or tetracyanoethylene as electron acceptors and aromatic hydrocarbons or substituted aromatics as electron donors have been prepared and the room temperature electrical resistivities measured on compressed microcrystalline material. A lowering of electrical resistivity is generally associated with complex formation. The results are discussed in terms of crystal structure and charge transfer complex theory.
Molecular Rotation in Crystals of N2 and CO
Authors: Kohin Barbara C.
Published: January 2005

Molecular rotation in low-temperature crystals of nitrogen and carbon monoxide is investigated. The following contributions to the crystal field hindering free rotation are taken into account: (a) the interaction of the molecular quadrupoles; (b) the effect of the anisotropic molecular polarizabilities; and (c) the short-range repulsive forces. The results of a theoretical calculation of the minimum-energy configuration at 0°K support the generally accepted structure; it is shown that the crystal field in this structure is axially symmetric at each lattice site. The Schrödinger equation for a rigid rotor in the crystal field is solved for the lowest rotational states of N2 and CO. It is found that a classical treatment of the rotation is not justified for these crystals due to the large separations of the lowest eigenvalues. The zero-point energy of rotation is found to be about half as large as the zero-point vibrational energy for these crystals.
Infrared Absorption Spectra of Alkali Metal Nitrates and Nitrites above and below the Melting Point
Authors: Greenberg J. , Hallgren Leander J.
Published: January 2005

The infrared absorption spectra of LiNO3, NaNO3, KNO3, RbNO3, CsNO3, NaNO2, and KNO2 above and below the melting point have been obtained by supporting the salts in the interstices of a fine mesh platinum screen. The frequencies observed have been assigned values according to the symmetry classification. The effects of temperature and cation size have also been noted.
Theory of Dilute High Polymer Solutions. II
Authors: Krigbaum W. R. , Carpenter D. K. , Kaneko M. , Roig A.
Published: January 2005

The second virial coefficient is calculated according to the smoothed distribution method. Our treatment differs from those of Flory-Krigbaum and Isihara-Koyama through inclusion of the numerous short-range intramolecular contacts arising by virtue of the connected nature of the chain. The result is to replace the previous F(X) by F(X, ρ), where the parameter ρ depends upon the ratio of the total number of intramolecular contacts to the number of long-range contacts counted using a radial segment distribution. The number of intermolecular contacts created when two molecules overlap is estimated by the use of an additional smoothed radial segment distribution which is assumed to be uniformly expanded by intramolecular excluded volume effects.

Comparison with experiment reveals that both the temperature and molecular weight dependences of A2 in the vicinity of the theta temperature are described in a reasonably quantitative fashion by the present treatment. In this case there are no adjustable parameters. Furthermore, satisfactory agreement is observed for good solvents using values for the thermodynamic interaction parameter deduced from intrinsic viscosity. In the limit ρ=1 the present treatment yields a result equivalent to those of FK and IK. We conclude that the latter underestimate the number of intramolecular contacts through neglect of the connected nature of the chain. In the other limit, ρ=0, a result approximating that of the Casassa-Markovitz treatment is obtained. We believe that their assumption of a spherical segment distribution about the initial point of contact results in an over-estimation of the number of intermolecular contacts.
Gamma Radiolysis of Propane
Authors: Birdwell B. F. , Crawford George W.
Published: January 2005

Propane gas has been irradiated with cobalt-60 gamma rays. The primary products formed by the decomposition of 0.9–3.2% of the original propane have been identified. Based on hydrogen yield, the relative yields of the products are: hydrogen (1.00), hexanes (0.70), ethane (0.32), methane (0.27), butanes (0.17), and pentanes (0.08).
Study of Molecular Integrals. I. Two-Center Exchange Integrals
Authors: Sahni R. C. , LaBudde C. D.
Published: January 2005

The evaluation of the two-center two-electron exchange integrals using prolate spheroidal coordinates and spherical coordinates is discussed. Estimates for the convergence rates of the infinite series which arise when both coordinate systems are used to evaluate the integrals are obtained.
Study of Molecular Integrals. II. Three-Center One-Electron and Two-Electron Integrals
Authors: LaBudde C. D. , Sahni R. C.
Published: January 2005

The evaluation of the three-center one-electron and two-electron integrals using spherical coordinates is discussed. Estimates for the convergence rates of the infinite series which arise in all cases are derived.
Transfer of Excitation Energy in Solid Solutions of Anthracene-Polystyrene and 9,10-Diphenylanthracene-Polystyrene
Authors: Basile L. J. , Weinreb A.
Published: January 2005

The transfer of excitation energy from the excited solvent to the solute has been studied as a function of solute concentration for solid solutions of anthracene and 9,10-diphenylanthracene in polystyrene. Transfer efficiencies and fluorescence spectra have been obtained for both systems. The fluorescent light pulse of both systems, when excited by electrons and uv radiation, was recorded and analyzed. Results indicate that radiative transfer predominates at low solute concentration, while at higher solute concentration the transfer process is predominantly nonradiative. Differences between the two systems are probably due to anthracene being chemically bound to the polymer chain while 9,10-diphenylanthracene is not.
Method for Investigating the Order of Chemiluminescent Reactions, the Diffusion Coefficient of the Labile Reactants, and the Catalytic Efficiency of Surfaces
Authors: Young Robert A.
Published: January 2005

A method is proposed for investigating the order of chemiluminescent reactions, the diffusion coefficient, and the catalytic efficiencies of surfaces for gas phase labile species. This method utilized the change in the decay rate of the labile reactants and of the light intensity. The decay rate of the labile species is controlled through adjustment of their diffusion loss to a catalytic surface.
Kinetic Theory of the Moderately Dense Rigid-Sphere Fluid. IV. Fluxes of Matter, Momentum, and Energy in a Mixture
Authors: Harris Robert A. , Rice Stuart A.
Published: January 2005

The perturbation solution of the modified Boltzmann equation is used to obtain the fluxes of matter, momentum, and energy. The fluxes are evaluated to first order in the gradients of density, flow velocity, and temperature, and are left in terms of the Sonine polynomial expansion coefficients. As an example, the calculation of the isothermal diffusion coefficient is carried out for the general case of unequal masses and radii. In the limit of identical particles, D is proportional to (2kT/m)12(N/vσ2) {[1/g(σ)]+(const/v)+···} .
X-Ray Scattering by a Cell-Model Liquid
Authors: Lund L. H.
Published: January 2005

The x-ray scattering by a cellular model of a liquid is characterized in terms of a cell-center pair distribution function and a function descriptive of the cell model employed. Presented also are cell-center pair distribution functions for liquid argon as calculated by inverting the theoretical formula for the scattered intensity.
Theory of ESR Linewidths of Free Radicals
Authors: Kivelson Daniel
Published: January 2005

A theory of ESR linewidths for substances in which the magnetic anisotropy is small and for which the orbital magnetism has been essentially quenched is developed. Nuclear quadrupole moments, zero field splittings, anisotropic Zeeman terms, and intramolecular electron-nuclear dipolar interactions, as well as motional and exchange effects are considered in the strong field case. The theory is developed in a manner that is particularly adaptable to the study of liquids but it is also applied to crystals since the resulting equations, though only applicable for small anisotropies, are particularly simple. The theory provides an extension of previous theories on ESR spectra in liquids. Several applications of the theory are discussed with particular emphasis on V4+ chelates. The theory of exchange in liquids, a phenomenon which is complicated by the noncommutivity of the motional and exchange Hamiltonians is considered in special detail. It is shown that this theory can be used to explain Hausser's results—the existence of an optimum viscosity for the observation of hyperfine structure.
Polycrystalline Resonance Line Shape of π-Electron Radicals
Authors: Sternlicht Himan
Published: January 2005

A general expression in the form of a multiple integral involving a delta function is derived for the polycrystalline spectra of radicals. The expression is exact when the hyperfine structure is due to the interaction of one proton with the unpaired electron. The extension to a system involving the interaction of a number of protons with the unpaired electron is straightforward but was not done here.

Because of the formidable integrations encountered when the complete spin Hamiltonian is used, a simpler case is considered to illustrate the technique developed. It is shown that if one assumes that IH, the nuclear spin component along the externally applied magnetic field, is a good quantum number, then the peak to peak separation of the broad doublet that is obtained bears a simple relationship to the hyperfine interaction.

For a properly chosen Cartesian axis system, the hyperfine spin Hamiltonian can be written as Hhf=hA SzIz+hBSxIx+hCSyIy.The peak to peak separation corresponds to the middle value of | A |, | B |, | C |.

The line shape for a C–H fragment with the unpaired electron in a carbon 2px orbital is worked out in detail assuming that IH is a good quantum number. Two peaks with very slightly asymmetric shoulders are obtained, the peak to peak separation being 61 Mc.
Absorption Lines of Cr3+ in Ruby
Authors: Low W.
Published: January 2005

The line spectrum of chromium in ruby has been investigated. New lines have been found at 14 795, 14 950, and 15 178 cm—1. These lines have been identified as belonging to the 2F1 triplet. Similarly, a line at 21 352 cm—1 has been assigned to the 2F2 triplet. It is shown that these levels originate from the 2G and 2D levels, respectively, with considerable admixture from the 2H level.
Vibrational Spectrum of Crystalline Potassium Hydroxide
Authors: Snyder Robert G. , Kumamoto Junji , Ibers James A.
Published: January 2005

The infrared spectrum of KOH has been obtained in the region 4000–300 cm—1. At 23°C the spectrum shows two broad bands, one at 3600 cm—1 and the other at 643 cm—1. At —180°C the O–H stretching band near 3600 cm—1 appears as a doublet. Splitting is shown to arise from coupling between the two OH— ions in the unit cell. Evidence is presented that indicates a small difference in the strengths of the hydrogen bonds in KOH and KOD. The first overtone of the O–H stretching band is found at 6868 cm—1 and from this a value of ωexe of 110±11 cm—1 is derived for KOH at —180°C. The 643 cm—1 band of KOH at 23°C is identified as a librational fundamental. At —180°C this band appears at 709 cm—1 together with bands at 840 and 671 cm—1; these latter two bands are also identified as librational modes. These librational frequencies lead to a considerably higher barrier to rotation of the OH— ions in KOH than in Mg(OH)2 or Ca(OH)2. This higher barrier is probably the result of the weak hydrogen bonding in KOH. Spectra of KOH–KOD mixtures are interpreted in terms of relatively small coupling between the librational modes of the hydroxyl ions and between the librational and translational modes.
Three Remarks on Molecular Orbital Theory of Complex Molecules
Authors: Parr Robert G.
Published: January 2005

Three suggestions are made and discussed concerning the generalized Hückel and related methods for treating the quantum chemistry of complex unsaturated molecules: (1) Justification for the assumptions of zero overlap and zero differential overlap resides in two facts: (a) For many molecules the atomic orbitals in the LCAO molecular orbitals may be replaced by the corresponding orthogonalized atomic orbitals of Löwdin, without effect on the molecular orbitals. (b) Integrals involving charge distributions which are products of orthogonalized atomic orbitals are small. (Observations previously made by several authors.) (2) Molecules isoelectronic with benzene are conveniently handled making use of molecular orbitals appropriate to the full benzene symmetry, for then deviations from benzene symmetry can be classified and treated systematically using symmetry combinations of basic integrals. (Formulas are given.) (3) The two-center coulomb repulsion integrals, previously dealt with by rather arbitrary semiempirical procedures, may be expanded by multipole expansion methods, leaving the independent multipoles of each atomic orbital as its defining theoretical or semiempirical characteristics.