bluuebunny/crossref_metadata_2025 huggingface dataset:
Deuteron Magnetic Resonance of Polycrystalline Deuteroammonia
Authors: Rabideau Sherman W. , Waldstein Peter
Published: January 2005

Deuterium magnetic resonance spectra of polycrystalline ND3 have been observed at 75°, 159°, and 185°K. The measured values of e2qQ/h were 156±7 kc/sec at 75°K, and 72.5±0.9 kc/sec at 159° and 185°K. The decrease at the higher temperatures has been attributed to rotational averaging. Single-crystal growth in the polycrystalline matrix was noted at the higher temperatures; it did not seriously interfere with the measurement of e2qQ/h. Proton second-moment measurements were made on a polycrystalline sample of NH3 at 75°K. The moment obtained was intermediate between the moments expected for the cases of fast and slow C3 reorientation. The rotational-transition temperature has been estimated to be 72°±2°K. A lower limit of 1.75 kcal/mole for the reorientational activation energy was estimated. An anomalous absorption peak was recorded in the center of the ND3 spectrum at 75°K. It may possibly be ascribed to a double-quantum transition.
Low-Frequency Region of the Infrared Spectrum of Matrix Isolated Vapors from Li2O(s)
Authors: Seshadri K. S. , White David , Mann D. E.
Published: January 2005

The infrared spectrum of matrix-isolated vapors from solid Li2O has been investigated in the region 60–350 cm−1. At 1640°K, where the polyatomic species Li2O(g) predominates, a single feature is found at 118 cm−1 for 7Li2O(g) and 112 cm−1 for 6Li2O(g). This is assigned to the bending mode v2. At higher temperatures, 1740°K, where the concentration of Li2O2(g) becomes significant, two additional bands are found. On the basis of 6Li–7Li isotopic shifts and relative intensities, it is possible to identify the bands in the region 240–260 cm−1 with the B1u out-of-plane mode of Li2O2(g) and those at 231–243 cm−1 to v2 of a new molecular species LiO2(g). A force constant analysis is given. On the basis of the present work it has been concluded that Li2O is most probably linear and LiO2 symmetric and nearly linear.
Franck—Condon Factors in Ionization: Experimental Measurement Using Molecular Photoelectron Spectroscopy
Authors: Turner D. W. , May D. P.
Published: January 2005

The photoelectron spectra excited by 21.21-eV photons in argon, krypton, xenon, hydrogen, nitrogen, carbon monoxide, oxygen, and nitric oxide have been re-examined using a 180° magnetic-field electron velocity analyzer. In favorable cases peaks corresponding to vibrational levels in the resulting positive ion are completely resolved giving directly the Franck—Condon factors. Where the vibrational peaks are not fully resolved, the relative order of intensities is apparent and comparison is made with calculations of the Franck—Condon factors. Vibrational structure associated with the second level of nitric oxide is observed for the first time, and this allows an accurate value (15.65 eV) to be attached to the adiabatic ionization potential of this level.
Delayed Luminescence of Organic Mixed Crystals. III. Decay Characteristics
Authors: Kinoshita M. , Misra T. N. , McGlynn S. P.
Published: January 2005

Decays of delayed luminescence in the following mixed crystals were investigated over a wide temperature range above 77°K: phenanthrene in biphenyl, naphthalene-h8 in biphenyl, naphthalene-d8 in biphenyl, and chrysene in biphenyl. It is shown that the kinetic model proposed by Sternlicht et al. explains results satisfactorily. The relationship τP=2τDF was found in the vicinity of the characteristic temperature, which is determined essentially by the energy difference between host triplet and guest triplet states and by the first-order phosphorescence decay rate. The activation energies for the annihilation process were obtained from the second-order analysis of decays observed above the characteristic temperature; this analyzing procedure differs from that used by Hirota and Hutchison.
Negative Temperature Coefficients of Electrical Conductance in Molten Salts
Authors: Grantham L. F. , Yosim S. J.
Published: January 2005

The electrical conductivities of molten CuCl, HgCl2, HgBr2, SnCl2, InI3, ZnI2, ZnCl2, TlCl, TlBr, TlI, and HgI2 were measured to temperatures as high as 1200°C. Maxima in conductivity as the temperature was increased were found in the first six salts. Since molten BiCl3, BiBr3, BiI3, CdI2, GaI3, pure water, and aqueous solutions containing weak and strong electrolytes also exhibit a conductivity maximum at elevated temperatures, it is concluded that this behavior is general to all fluids at sufficiently high temperature and sufficiently reduced density. These maxima in fused salts are attributed to increasing covalency or ionic association as the density decreases.
Diffusion of Triplet Excitons in Crystalline Anthracene
Authors: Levine Menahem , Jortner Joshua , Szöke Abraham
Published: January 2005

In this work we present an experimental study of triplet-exciton diffusion in crystalline anthracene. Triplet-exciton lifetime was determined by the time intermittency method, while the diffusion coefficients and the components of the diffusion tensor were determined by the space intermittency technique. From the comparison of the experimental data with the results of the theoretical analysis we conclude that:

(a) The magnitude of the diffusion coefficient for triplet excitons [D=(2.0±0.5)×10−4cm2/sec] yields a strong support for the strong scattering random-walk model for triplet-exciton migration in crystalline anthracene.

(b) The diffusion tensor of triplet excitons in crystalline anthracene was found to be isotropic.

(c) The isotropy of the diffusion tensor in the ab plane can be properly accounted for in terms of the calculated intermolecular electron exchange and charge-transfer interactions.
Adsorption of Potassium on Tungsten: Measurements on Single-Crystal Planes
Authors: Schmidt L. D. , Gomer R.
Published: January 2005

Work functions of the (110), (211), (100), and (111) regions of a thermally annealed tungsten field emitter were measured as a function of potassium coverage. Immobilely adsorbed layers yielded absolute dipole moments, permitting estimates of adsorbate charge. The results at low coverage are μ110=15.7 D, μ211=13.6 D, μ100=11.5 D, μ111=9.5 D, with μ defined as 2qd0=Δφ/2πn. At coverages θ≳0.6 there is evidence of higher layer formation and field enhancement. Work functions after thermal equilibration in combination with φ-vs-n data for immobilely adsorbed deposits yielded coverage anisotropies under equilibrium conditions. At θ̄≈0 n110/n̄=40,n211/n̄=0.35,n111/n̄<0.04,n100/n̄<0.01. As θ increases the anisotropies decrease, and for θ̄≳0.5 the ratios n̄→1 for all regions except 100. The corresponding differences in heats of adsorption at θ̄≈0 are less than 0.4 eV for all regions except possibly 100, with binding strongest on 110. A quantum-mechanical model is briefly sketched, and a quasistatistical treatment of alkali adsorption is outlined. It is shown that the small differences in H for substrate regions of considerably different work function and structure can result from the near cancellation of variations in explicitly electrostatic effects and exchange effects.

The φ-vs-n curves on single planes can be fitted by a simple depolarization model leading to values of the ad-complex polarizability of 26 Å on (110), 46 Å on (211), 35 Å on (100), and 29 Å on (111). It is shown that the concept of ad-complex polarizability follows naturally from the statistical model.
Possible Experimental Equivalence of the Gibbs—DiMarzio and Free-Volume Theories of the Glass Transition
Authors: Eisenberg Adi , Saito Shogo
Published: January 2005

The observation is made that a straight line with a slope of 1 is obtained when the two parameters of the Gibbs—DiMarzio theory are plotted against each other. The two parameters are Δε/k, the energy difference between the trans and gauche conformations of a hydrocarbon-type polymer chain, and 2α/k, the ``hole formation energy.'' The identity (practically within experimental error) of these two parameters implies that the free volume V0 at Tg is apparently constant since both 2α/k and Δε/k are functions of V0 alone. Furthermore, the product TgΔα (where Δα is the difference in the cubic expansion coefficients above and below Tg) is also a constant, since that, too, is a function only of V0. The ``universal'' value of V0 is 0.037, and that of TgΔα is 0.116, extremely close to the value found by Simha and Boyer. Thus, it seems that, within experimental error, the Gibbs—DiMarzio theory and the classical free-volume theory are practically equivalent, at least for the homopolymers examined here.
On the Hyperfine Structure of InH and the Theory of the Hyperfine Structure of Molecules in Hund's Case (C)
Authors: Freed Karl F.
Published: January 2005

The hyperfine structure in the 3Π1 state of InH, which deviates strongly from the magnetic hyperfine interval rule, is explained by the electric quadrupole interaction of the In nucleus. The quadrupole coupling constant for the 3Π1 (v=0) state eQqπ is +0.1 cm−1±100%. The off-diagonal quadrupolar interaction, namely the eQ sin2θ exp (±2iφ)/r3 part, gives an F-dependent contribution to the Λ-type doubling of the 3Π1 (v=0) state, eQq′ = +0.066 cm−1(2000 Mc/sec)±50%. An upper limit to the quadrupole coupling constant of the X 1Σ+ (v=0) state is ∼|eQqx|≳0.07 cm−1±100%.

The theory of hyperfine structure in Hund's Case (c) is discussed, and the matrix elements of the hyperfine interactions are evaluated for two Case (c) coupling schemes for a diatomic molecule with two nuclear spins. The matrix elements are evaluated by the generalization of Van Vleck's method of reversed angular momenta to spherical tensor form.
ESR of Free Radicals Trapped in Inert Matrices at Low Temperature: P, PH2, and As
Authors: Morehouse Roger L. , Christiansen Jørn J. , Gordy Walter
Published: January 2005

Free radicals produced by γ irradiation of PH3 and of AsH3 in dilute solution in a krypton matrix at 4.2°K have been studied with electron spin resonance. For the PH3 solution, PH2 radicals as well as H and P atoms were observed. For the AsH3solutions, only H and As atoms were observed. For the PH2 radicals, the observed ESR constants are: Af(31P) = 80 G, Af(H) = 18 G, and g = 2.0087. For the P atoms, Af(31P) = 30.5 G and g = 2.0027. For the As atoms, Af(75As) = 11.2 G and g= 1.9975. From the P and H couplings it is concluded that the P bonding orbitals of PH2 are sp2 hybrids with 27% scharacter. From the line shapes it is concluded that the PH2 radical rotates in the krypton matrix.
Normal-Coordinate Treatment and Computation of Coriolis Coefficients and Ground-State Centrifugal-Distortion Constants of Digermane, Disilane, Methylgermane, and Methylsilane
Authors: Clark Edward A. , Weber Alfons
Published: January 2005

A normal-coordinate calculation was performed for digermane, disilane, methylgermane, and methylsilane as well as for their deuterated analogs which are of the symmetric-top type. Vibrational frequencies, Coriolis-coupling coefficients, and ground-state centrifugal-distortion constants were computed using the best set of force constants obtained.
Flash Desorption and Isotopic Mixing of Hydrogen and Deuterium Adsorbed on Tungsten, Iridium, and Rhodium
Authors: Mimeault V. J. , Hansen Robert S.
Published: January 2005

Flash desorption of hydrogen from tungsten, iridium, and rhodium dosed at 100° and 300°K was investigated together with isotope mixing in coadsorbed mixtures of hydrogen and deuterium.

The desorption of hydrogen from tungsten, iridium, and rhodium dosed at 300°K proceeds by a second-order process with an activation energy of desorption well represented by ΔH=ΔH0—αn. At low surface coverages, values of 35, 24, and 18 kcal/mole, respectively, were obtained for ΔH0; the parameter α was determined from desorption curves at higher initial coverages and was found to be 28±2, 14±1, and 24±2 kcal/mole (1015 molecules/cm2)−1, respectively.

The desorption spectrum of hydrogen from these metals dosed at 100°K contains two peaks, α and β. The distribution of the isotopes in the desorbed phase formed from coadsorbing H2 and D2 indicates that the α peak is due to an atomic species in the case of iridium and rhodium and a molecular species in the case of tungsten.
Extension of Electron Affinities and Ionization Potentials of Aromatic Hydrocarbons
Authors: Becker Ralph S. , Chen Edward
Published: January 2005

The absolute molecular electronegativities for 14 aromatic hydrocarbons are reported. For the hydrocarbons considered, a linear relationship exists between the electron affinity and the energy of the 1La transition. The molecular electronegativity for some eight aromatic hydrocarbons is approximately constant. On this basis, it is possible to predict some ionization potentials which are in excellent agreement with recent experimental values. It does not appear reasonable to relate the intercept resulting from extrapolation of the aforementioned plot to hν=0 to the work function of graphite. Based on the measured electron affinities, it is possible to deduce a relationship with methyl affinities and calculate ΔEsol between neutral hydrocarbons and their mononegative ions. Certain theoretical approaches can be successfully employed to estimate electron affinities of aromatic hydrocarbons.
Barrier to Internal Rotation in Ethane
Authors: Clementi E. , Davis D. R.
Published: January 2005

A series of SCF LCAO MO computations for the ethane molecule are reported for both the staggered and eclipsed form. The obtained wavefunctions are better than those previously reported in literature. From this work the following conclusions can be derived. (1) The height of the internal rotation barrier is rather insensitive to the choice of the basis set. This explains the good agreement between computed and experimental barrier height found by Pitzer and Lipscomb. These authors obtained a total energy of −78.99115 a.u. for the staggered form and −78.98593 a.u. for the eclipsed form. Our best computation gives a total energy of −79.10824 a.u. for the staggered form and −79.10247 a.u. for the eclipsed form. The experimental barrier height is 0.0048±0.0005 a.u. (3.03±0.3 kcal). (2) The SCF LCAO MO functions are adequate in reproducing the barrier; therefore correlation effects are rather unimportant. As a consequence, these computations support indirectly the simple electrostatic model advanced, for example, by Karplus and Parr.
``Multiple-Scattering'' Model for Polyatomic Molecules
Authors: Johnson Keith H.
Published: January 2005

The ``multiple-scattering'' technique of determining energy bands in solids is modified for the problem of calculating bound one-electron eigenstates of polyatomic molecules. The computational simplicity and applicability of this method to molecules of arbitrary complexity are dependent on the adoption of a model Hartree—Fock Hamiltonian based on the Slater approximation to the exchange potential and on the assumption of truncated spherically averaged potentials. The composite wavefunctions are expanded in rapidly convergent partial-wave series around each atomic site. For molecules of moderate size, the calculations can easily be carried to self-consistency within the spherical approximation, and first-order perturbation theory can be applied to correct for the nonspherical components of the potential. Emphasis is placed on the advantages of this technique as a first step in calculating the theoretical electronic spectra of complex polyatomic systems.
Vibrational Intensities. XV. Error Treatment and Its Application to the Methyl Halides
Authors: Russell Joel W. , Needham C. D. , Overend John
Published: January 2005

The estimation of statistical errors in the dipole-moment derivatives, ∂p/∂Si, is described. Account is taken of contributions from random errors in the experimental intensity data, the intramolecular force constants, the molecular geometry, and the harmonic frequencies. It appears that generally the first two contributions are of similar importance and the second two negligible. As a detailed example of this treatment we have reworked the vibrational intensities of methyl fluoride, chloride, bromide, and iodide and their deuterium derivatives using new estimates of the normal coordinates. The calculated rotational contributions to the dipole-moment derivatives with respect to symmetry coordinates have been corrected.
Temperature Dependence of the High-Frequency Moduli of Vitreous B2O3
Authors: Capps W. , Macedo P. B. , O'Meara B. , Litovitz T. A.
Published: January 2005

Measurements of ultrasonic velocity allowed the calculation of the high-frequency shear and bulk moduli of B2O3 from 80° below to 300°C above the glass transition. The temperature dependences of these moduli were found to be consistent with a semiempirical extension of the theory of Zwanzig and Mountain.
Interpretation of the Electron-Spin Resonance Spectrum of the Methyl Radical
Authors: Karplus Martin
Published: January 2005

A valence-bond calculation of the proton hyperfine splitting in the electron-spin resonance spectrum of the methyl radical has been performed. The splitting was computed as a function of the angular configuration of the molecule. For the planar radical a splitting of 27±5 gauss was found, in agreement with experimental measurements on irradiated solids. However, the functional dependence of the splitting on angular configuration and the uncertainty in certain of the molecular integrals are such that deviations from planarity of 10–15° cannot be definitely excluded.
Structures of Dimethyl Ether and Methyl Alcohol
Authors: Kimura Katsumi , Kubo Masaji
Published: January 2005

The molecular structures of dimethyl ether and methyl alcohol were determined in gaseous state by means of the sector-microphotometer method in electron diffraction. The structural information was derived from the resolution of radial distribution curves. It was confirmed that a dimethyl ether molecule exerts hindered internal rotation with a potential minimum at the C2v configuration. The most probable values for the bond distances and the bond angles are for dimethyl ether: C–O = 1.416±0.003 A, C–H = 1.094±0.006 A, ∠COC = 111.5°±1.5°; and for methyl alcohol: C–O = 1.428±0.003 A, C–H = 1.095±0.010 A, O–H = 0.960±0.015 A, ∠COH = 109°±3°. The results on methyl alcohol agree with those of microwave determinations. The observed values of vibrational amplitudes are in good agreement with those computed theoretically.
Viscosities of Some Undercooled Liquid Alkyl Halides
Authors: Denney Donald J.
Published: January 2005

The viscosities of i-butyl bromide, i-amyl bromide, and i-butyl chloride have been measured over a temperature range in which η changes from 102 poise to about 108 poise. The temperature dependence of η is very close to that of the dielectric relaxation time τ indicating the similarity of the molecular processes involved. This similarity thus appears to apply to ``nonassociated'' polar liquids as well as to hydrogen bonded liquids.
Chemisorption of Nitrogen on Tungsten
Authors: Kisliuk P.
Published: January 2005

The amount of nitrogen chemisorbed on a polycrystalline tungsten ribbon has been measured as a function of the temperature of the ribbon and the pressure in the region of less than one monolayer. By assuming the condensation coefficient to be insensitive to the temperature of the gas, values of the thermodynamic functions are determined. It is found that N2 is adsorbed on tungsten as atoms with a heat of adsorption of 5.0 ev per molecule (±10%) independent of coverage over the experimental range of coverage. In the temperature range 1150–1670°K the differential entropy of adsorption is of the order expected for adsorption on localized sites, with a moderate contribution from the vibrational degrees of freedom.
Mass Spectrometric Study of Heats of Sublimation of Dysprosium, Samarium, Thulium, and Ytterbium
Authors: Savage William R. , Hudson Donald E. , Spedding Frank H.
Published: January 2005

The flux of atoms from a Knudsen-type effusion cell has been studied by means of a mass spectrometer. The heat of sublimation was obtained from the dependence of the ion current upon the cell temperature by means of the Clausius-Clapeyron equation. The method was used to obtain heat of sublimation values for dysprosium, samarium, thulium, and ytterbium. The results were: Dy, 69.3±0.6 kcal/mole for vaporization at 1215°K; Sm, 48.7±0.4 kcal/mole for vaporization at 811°K; Tm, 56.2±0.4 kcal/mole for vaporization at 937°K; and Yb, 39.5±0.5 kcal/mole for vaporization at 667°K.
Reversible Variations of Sensitivity in Certain Cadmium Sulfide and Selenide Photoconductors
Authors: Bube Richard H.
Published: January 2005

Measurements of photoconductivity in certain CdS and CdSe crystals show the existence of relatively shallow acceptor levels with ionization energy in the 0.1 to 0.3 ev range. The photosensitivity normally associated with holes captured by centers with an ionization energy of 1.0 ev in CdS, and 0.6 ev in CdSe, is markedly decreased at room temperature when these shallow acceptor levels effectively replace the normal deeper levels. Such a photosensitivity decrease can be caused by illumination at room temperature for a period of time, or by heating to above 100°C, but less than about 150°C, followed by cooling to room temperature. The photosensitivity at room temperature can be increased again by heating the crystals to over about 150°C, and quenching. The process is completely reversible. In CdSe there appears to be a single level with ionization energy of 0.3 ev, whereas in CdS there appears to be a distribution of levels with ionization energies varying from about 0.15 ev to the normal 1.0 ev. The presence of the shallow levels makes possible a much faster decay of photocurrent at liquid nitrogen temperature than is usually found in sensitive crystals.
Low-Temperature Phase Transition of Crystalline Hexamethylbenzene. II
Authors: Schnepp O.
Published: January 2005

The absorption spectrum of the ab plane of crystalline hexamethylbenzene in polarized light has been studied. This spectrum is forbidden and isotropic below the λ-point transition at 110°K and allowed and very anisotropic above this temperature. It is proposed that these results support the conclusions presented in an earlier paper based on the spectrum of the bc plane. A crystal field calculation of the intensity expected to be induced by this perturbation is shown to support also the conclusion that the molecule is slightly distorted in the high temperature crystal modification. A mechanism for the phase transition is proposed and is based on the assumption that the methyl groups begin to rotate about the C–C bond at 110°K.
Temperature-Pressure-Structure Effects on the Viscosity of Several Higher Hydrocarbons
Authors: Lowitz D. A. , Spencer J. W. , Webb W. , Schiessler R. W.
Published: January 2005

The viscosity of fourteen very pure high molecular weight hydrocarbon liquids has been determined at six temperatures, ranging from 37.78°C to 135°C, and at pressures ranging from atmospheric to 3400 bar, by use of a rolling-ball viscometer. For nine of the liquids whose PVT data were not available, a flexible bellows piezometer was used to determine the density between the same limits of temperature and pressure as employed for the viscosity measurements. The hydrocarbons selected vary in molecular weight from 268.5 to 535.0 and comprise several structural symmetry families involving progressive cyclization to cyclohexyl, phenyl, and decalyl groups. Also included are an alkylnaphthalene, an alkyldecahydronaphthalene, two hydrochrysenes, an homologous series of branched paraffins, and a series of 1,1-diphenylalkanes. Correlations are made of structure with viscosity, rate of change of viscosity with pressure, and enthalpy of activation for viscous flow. The effects of molecular weight and of molecular structure on viscosity are discussed.
Absorption of Acyclic Oxygen Compounds in the Vacuum Ultraviolet. I. Alcohols
Authors: Harrison Anna J. , Cederholm Betty J. , Terwilliger Margery A.
Published: January 2005

A fluorite prism vacuum spectrograph and a hydrogen lamp have been used to determine the 50 000- to 65 000-cm—1 absorption spectra of water, methanol, ethanol, 1-propanol, and 2-propanol in the vapor phase at 22°C.
Electron Spin Resonance Studies of Irradiated Teflon: Effects of Various Gases
Authors: Rexroad Harvey N. , Gordy Walter
Published: January 2005

The radical produced by x- or γ-irradiation of polyfluoroethylene (Teflon) in a high vacuum is shown to have five F atoms with nuclear coupling to the electron spin, four with equivalent coupling of 33 gauss each and a fifth with coupling of 92 gauss. The radical is probably of the form XCF2CFCF2Y, where X and Y represent the continuing Teflon chains with no significant electron spin density. Molecular oxygen was found to combine with undetectable radicals or ions in the irradiated Teflon to produce a new resonance. Carbon monoxide alters the latter resonance to a different one while H2, NO, and ionized air destroy it. The resonance of the fluorocarbon radical is also nullified by H2 and NO. When Teflon is irradiated under an atmosphere of NO gas, a triplet resonance structure apparently arising from N14 nuclear interaction is produced. The triplet can also be produced by admission of NO to a sample of Teflon previously irradiated in a vacuum.
Absorption Spectrum of Fluorine in the Vacuum Ultraviolet
Authors: Iczkowski Raymond P. , Margrave John L.
Published: January 2005

The absorption spectrum of F2 has been observed in the vacuum ultraviolet region. A special windowless absorption apparatus and a Lyman discharge light source were used in combination with a one-meter normal incidence spectrograph.

A Rydberg series establishes the ionization potential of F2 as 15.7 ev. From a progression of bands at 874 A, one can deduce the dissociation energy of fluorine as 37.5±2 kcal/mole. The binding energy of F2+ is 3.3 ev. The low value of the ionization potential is consistent with the observed low value of the dissociation energy.
Low-Temperature Fluorescence Spectra and Crystal Field Splittings of Rare-Earth Activated SrS Phosphors
Authors: Keller S. P. , Pettit G. D.
Published: January 2005

As a continuation of an earlier work, SrS phosphors, singly activated with rare-earth ions have been excited with uv irradiation, at 77°K. The resultant visible fluorescent emissions have been measured and correlated with crystal field splittings of energy levels. Energy level diagrams are presented with possible term assignments. Where possible, comments are made about the symmetry of the activator sites.
Paramagnetic Resonance of Bis-Cyclopentadienyl Vanadium
Authors: McConnell H. M. , Porterfield W. W. , Robertson R. E.
Published: January 2005

The paramagnetic resonance spectrum of a benzene solution of bis-cyclopentadienyl vanadium shows a g factor equal to 2.00 and a V51 isotropic hyperfine splitting equal to 77 Mc. The small V51 hyperfine splitting demonstrates that none of the three odd electrons in this sandwich compound spends an appreciable part of its time in a 4s atomic orbital of the vanadium atom. The observed spectroscopic splitting factor shows that the orbital ground state is a singlet. This result signifies that one of the three unpaired electrons in this substance must be in an orbital of a1g symmetry, and that the other two electrons must be in orbitals of eg symmetry. This latter conclusion is in good agreement with theoretical orbital energy levels derived by a number of investigators.

The paramagnetic resonance spectrum of an air oxidation product of bis-cyclopentadienyl vanadium has been observed. The spectroscopic splitting factor is g=1.99 and the hyperfine splittings are 210 Mc. It is suggested that the oxidation product may be the neutral vanadyl sandwich, VO (C5H5)2.
Thermoluminescent Properties of Calcite
Authors: Medlin W. L.
Published: January 2005

The effects on thermoluminescent properties of adding certain impurities to calcite have been investigated. The impurities were added as coprecipitants and their concentrations in the solid were determined by colorimetric techniques. Each of the ions which ordinarily function as activators was added but only Mn++ and Pb++ were found to be activators in calcite. Mn++ is responsible for two prominent peaks in the glow curve at 350 and 470°K which coincide with two of the three prominent peaks commonly found in natural samples. Pb++ produces two peaks of lower intensity at 300 and 410°K. Fe+++, Co++, and Ni++ quench the Mn++ and Pb++ luminescence and Co++ or Ni++ in the presence of Mn++ results in a 600°K peak in the glow curve which coincides with the third peak generally found in natural samples. The results for efficiency of luminescence as a function of activator concentration for the Mn++, Pb++, and Mn–Co and Mn–Ni glow peaks are presented and discussed.
Charge-Exchange Cross Sections of Argon Ions in Hydrogen Molecules
Authors: Karmohapatro S. B.
Published: January 2005

Charge-exchange cross sections of low-energy argon ions in hydrogen are calculated by the semi-quantum-mechanical impact parameter method, improved with a better approximation of the wave functions. Cross-section curves for the reactions in the different states are compared with the experimental curve so that the part of each of the different reactions in the experiment may be evaluated approximately.
High-Temperature Gas Viscosities. II. Nitrogen, Nitric Oxide, Boron Trifluoride, Silicon Tetrafluoride, and Sulfur Hexafluoride
Authors: Ellis C. P. , Raw C. J. G.
Published: January 2005

The viscosities of nitrogen (from 700° to 1000°), nitric oxide (from 100° to 1000°), boron trifluoride (from 180° to 500°), silicon tetrafluoride (from 200° to 330°C), and sulfur hexafluoride (from 200° to 850°C) have been measured using a specially constructed silica apparatus described in Part I of this series. In addition, our previous results for SiF4 have been recalculated in the low-temperature range down to room temperature. These results are discussed from the point of view of the intermolecular forces, and the molecular interaction parameters are compared with those calculated from data on gas viscosities in the lower temperature ranges. The results show the temperatures at which thermal dissociation of the compounds becomes important, and the viscosity measurements are not carried very far beyond these temperatures.
Statistical Computation of Radii of Gyration and Mean Internal Dimensions of Polymer Molecules
Authors: Wall F. T. , Erpenbeck J. J.
Published: January 2005

A Monte Carlo numerical method has been employed for the computation of the mean-square separation between pairs of elements i and j, 〈Rij2〉, and the mean-square radius of gyration, 〈Sn2〉, for an n-segment coiling type polymer molecule. A restricted random walk was used as a model for the polymer, and the average dimensions in question were calculated for random samples of nonintersecting walks generated by means of a high-speed digital computer. 〈Rij2〉 has been found to be a rather complicated function of i/n and j/n, depending upon the position in the chain as well as upon the contour length of the segment between i and j. The mean-square radius of gyration was found to be proportional to the average square end-to-end distance, as for simple unrestricted random walks, but the constant of proportionality differs from the value of ⅙ which is applicable in the absence of the excluded volume effect. The exact value of the ratio of the two quantities depends upon whether the molecule is constrained to 2 or 3 dimensions.
Effect of Paramagnetic Ions on the Nuclear Magnetic Resonance of O17 in Water and the Rate of Elimination of Water Molecules from the First Coordination Sphere of Cations
Authors: Connick Robert E. , Poulson Richard E.
Published: January 2005

Observations have been made on the relative effectiveness of various paramagnetic ions in broadening the nuclear magnetic resonance of O17 in water and it is inferred that the relaxation occurs almost entirely in the first coordination sphere of all of the cations studied except chromic ion. Accepting this hypothesis, it is possible to calculate lower limits for the rates of exchange of bulk water molecules with those in the first coordination sphere of the cations. For ferric ion the lifetime of a coordinated water molecule is equal to or less than 10—6 second at room temperature.
Heat Capacities and Thermodynamic Properties of the Iron Tellurides Fe1.11Te and FeTe2 from 5 to 350°K
Authors: Westrum E. F. , Chou Chien , Grl/nvold F.
Published: January 2005

Heat capacities of the two iron telluride phases, Fe1.11 Te and FeTe2, were measured in the range 5 to 350°K. In Fe1.11Te a cooperative type of transformation was observed at about 63°K involving an entropy increment of 0.57 cal/mole °K. The thermodynamic functions were evaluated and the values of Cp, S°—S0°, and (H°—H0°)/T at 298.15°K are 13.15, 21.272, and 9.575 cal/mole °K, respectively, for Fe1.11Te, and the values of Cp, S°—S0°, H°—H0°, and — (F°—H0°)/T for FeTe2 are 17.60 and 23.940 cal/mole °K, 3567.4 cal/mole, and 11.975 cal/mole °K, respectively.
Formation of Ozone from Atomic Oxygen at Low Temperatures
Authors: Ruehrwein R. A. , Hashman J. S.
Published: January 2005

Oxygen was passed through an electrodeless discharge and was condensed, either alone or mixed with diluent gases, at liquid helium temperature. On warming through a temperature range of 13–30°K the blue solid deposits became more deeply colored. The amount of ozone formed was determined. It was concluded that ozone was formed upon condensation by the predominant reactions (1) and (2) O+O=O2,O+O2=O3.The experimentally observed conversion to ozone of 58% agreed well with that calculated from a rate law with k1/k2=1.3. The activation energy of these reactions was estimated to be less than 1.5 kcal.
Statistical Mechanical Theory of Thermal Diffusion in Binary Liquid Solutions
Authors: Bearman Richard J.
Published: January 2005

The statistical mechanical theory of thermal diffusion in binary solutions is developed from the point of view of the pair space linear relations which have been used previously to derive theories of the heat of transport and thermal conductivity. The thermal diffusion factor is obtained in terms of statistical mechanical averages over the equilibrium radial distribution functions, and when assumptions of the theory of regular solutions are introduced into the general expression, we find that it is related to the molar volumes, thermal expansion coefficients and compressibility coefficients of the pure components and to the self-diffusion coefficients in the mixture.
Proton Magnetic Resonance Study of the Structure of Potassium Pentaborate
Authors: Silvidi A. A. , McGrath J. W.
Published: January 2005

The proton magnetic resonance absorption spectrum of monocrystalline potassium pentaborate has been obtained experimentally at room temperature using a Pound-Watkins spectrometer. The results indicate that there are two waters of hydration per molecule. The interproton distance is 1.60±0.02 A. The p—p axes lie in the b—c plane of the crystal and make an angle of 93°±4° with each other. Using experimental data together with consideration of interatomic distances and hydrogen bonding the remaining hydrogens are tentatively located in the molecule.
NMR Study of Ferrocene, Ruthenocene, and Titanocene Dichloride
Authors: Holm C. H. , Ibers James A.
Published: January 2005

The line widths of the proton magnetic resonance absorption spectra and the spin-lattice relaxation times for polycrystalline samples of ferrocene, ruthenocene, and titanocene dichloride were measured as functions of temperature, and are interpreted in terms of reorientation of the cyclopentadienyl rings about their fivefold axes. At low temperatures such reorientation is interpretable in terms of an activated process governed by a single correlation time, and the barrier restricting reorientation is obtained. At higher temperatures for these substances, as well as for benzene, such an interpretation is not suitable, and a hypothesis involving the coupling and uncoupling of adjacent rings taking part in reorientation is proposed to account for the data.
Structure and Adsorption Characteristics of Clean Surfaces of Germanium and Silicon
Authors: Schlier R. E. , Farnsworth H. E.
Published: January 2005

Diffraction patterns obtained from atomically clean germanium surfaces contained half-integral order beams in (110) azimuths for both (100) and (110) surfaces and in all azimuths for the (111) surface. These results are considered to be due to displacements of surface atoms from their normal bulk lattice positions in the surface plane. Adsorption of oxygen on all of these surfaces extinguished all of the diffraction beams which were not integral order.

In addition to the normal surface lattice spacings of clean (111) and (100) surfaces of silicon, there were surface structures with larger spacings, most of which depended on the conditions of ion bombardment and/or subsequent heat treatment. Two such structures have been observed for the (100) surface of silicon; one is a double-spaced lattice in the (110) azimuth, similar to that for germanium, and the other has a spacing about 8% greater than that of normal silicon and was obtained only after radiation quenching of the crystal from 1000°C. Two large-spaced structures were observed for the (111) surface. All of these structures were extinguished by exposure to oxygen. Evidence is presented which indicates that these structures were not due to contamination but to the silicon itself.

The method of determining the kinetics of gas adsorption from the low-energy electron diffraction beams is outlined and the calculations of the fractional coverage and sticking probability are presented for oxygen. For silicon crystals, the calculations of surface coverages and sticking coefficients for oxygen were found to depend on the preceding treatments of the crystals. The rate of adsorption of oxygen was proportional to the pressure, at least for pressures below 10-6 mm Hg, and depended on the preceding treatments of the crystals. After oxygen adsorption, the clean germanium surface could be regenerated by heating at 500°C for 30 min and for silicon it was regenerated by heating at 900°C for a few minutes. A comparison with results of other observers is given.
Conjugation and Polar Effects in Butadiene
Authors: Berry R. Stephen
Published: January 2005

Various valence bond structure functions are projected onto approximate ground-state wave functions of butadiene. The most important structure, C=C–C=C, contributes approximately 70% of the total. The next most important structure corresponds to two attractive dipoles and contributes over 40% to the ground state, while structures with double bonds between the central carbons contribute relatively little. It appears that ionic contributions may be important to the central carbon-carbon bond length, with the dipole-dipole interaction behaving like an effective repulsion because of the variation of the electronic wave function. The problem of the nonorthogonal valence bond representation is examined: it is found that conjugation is strongly inherent even in a ``nonconjugated'' structure C=C–C=C, and that conjugation and dipolar interaction are nearly separable.
Experimental Test of the Volmer Theory of Heterogeneous Nucleation
Authors: Twomey S.
Published: January 2005

The prediction of the Volmer theory that the critical supersaturation for nucleation from the vapor phase on a flat surface depends upon (1−cosφ2)(2+cosφ), where φ is the contact angle of the condensate on the surface, has been tested experimentally. Critical supersaturations for visible fogging on test surfaces coated with various transparent plastics were found to agree within observational error with the theoretical values computed for the observed contact angles.
Strong Coupling in Nuclear Resonance Spectra. I. The Five-Spin System of trans-Propenylbenzene
Authors: Fessenden R. W. , Waugh J. S.
Published: January 2005

Energy levels and allowed transitions are calculated for a system of five spin-½ particles of the type ABX3. An extension to the more general system ABC3 is made by perturbation theory. The results are applied to an analysis of the proton resonance spectrum of trans-propenylbenzene, and it is found that at least one spin-spin coupling constant is negative. An ``anomalous'' spectrum previously reported, which shows superficial resemblances to the one studied here, is explained by assuming the presence of an impurity.
Pure Quadrupole Resonance Determinations of Molecular Charge Distributions. II. Substituted Pyrimidines
Authors: Hooper H. O. , Bray P. J.
Published: January 2005

The amount of double-bond character of the carbon-chlorine bond at the 2, 4, and 6 positions in twelve substituted chloropyrimidines has been estimated from the chlorine pure quadrupole resonance frequencies. If it is assumed that the nitrogens have a weak inductive effect upon adjacent ring positions, then the calculated values for the amount of double-bond character agree quite well with data obtained from experiments employing Zeeman splitting techniques applied to pure quadrupole resonance spectra.
Structure of K2CuF4. New Kind of Distortion for Octahedral Copper(II)
Authors: Knox Kerro
Published: January 2005

Potassium tetrafluorocuprate(II) has been shown by single-crystal x-ray data to be isostructural with K2NiF4. The tetragonal unit cell, with a=4.155±0.005 and c=12.74±0.01 A, contains two formula units. The ions are in the following positions of space group D4h(17)−I4/mmm:2Cu in (a),4FI in (c),4K and 4FII in (e) with zK=0.356 and zFII=0.153. In this structure the Cu(II) ions are surrounded by a distorted octahedron of F— ions with two nearest neighbors at 1.95 A and 4 next nearest at 2.08.

This is the first time that copper(II) in essentially octahedral coordination has been proved to have a tetragonal distortion such that c/a for the distorted octahedron is less than one. This experiental result is contrary to the theoretical calculations of Öpik and Pryce but in accord with the refined computations of Liehr and Ballhausen.
Trapped NH2 Radicals at 4.2°K
Authors: Robinson G. Wilse , McCarty Maclyn
Published: January 2005

A study has been made of the electronic absorption spectrum of the NH2 radical trapped in an argon matrix on a liquid helium cooled surface. The radical is produced in a microwave discharge of argon mixed with a small amount of parent molecule, ammonia or hydrazine. The long effective absorbing path is illustrated by the presence of new bands of NH2, too weak to have yet been observed in the flash photolysis spectrum. That the radicals have also been found in moderate concentration from low-pressure discharges containing hydrogen and nitrogen in many forms indicates that they are easily built up from smaller fragments, a fact which may be important in the explanation of the origin of these radicals in comets. The radical is positively identified by the excellent correlation between the low temperature spectrum and the gas-phase spectrum recently analyzed by Ramsay, and in agreement with this analysis only alternate bands appear strongly at 4.2°K. The observed features, which represent rotational lines of the electronic transition, surprisingly enough, are less than 3 cm—1 wide, the lack of broadening indicating that the radicals are situated in equivalent matrix sites, possibly in an ordered argon crystal lattice, and evidence is presented which shows that NH2 experiences nearly free end-over-end rotation in the matrix. The experimentally observed small population of the lowest state of para-NH2 shows a breakdown of the usual s↮a selection rule for exchange of identical nuclei. A determination from relative intensity measurements of interaction constants for Fermi resonance between certain 0ν2′0 and 1(ν2′−4)0 levels shows that the intensity of the latter is caused primarily by the resonance and not by the Franck-Condon effect.
Interpretation of the Infrared Spectra of the Solid Hydroxylammonium Halides
Authors: Frasco D. L. , Wagner E. L.
Published: January 2005

Infrared spectra of sublimed films of hydroxylammonium and deuterohydroxylammonium chlorides, bromides, and iodides have been obtained at 25°, —78°, and —180°C from 4000 to 400 cm—1. Satisfactory vibrational assignments for the hydroxylammonium ion can be made on the basis of an ionic model in which one end of the ion (H3NO) is axially summetric (C3v) and the other end (OH) is of Cs symmetry. A normal coordinate treatment based on a simplified valence force potential with ten constants reproduces 13 of the 18 frequencies of the hydroxylammonium and deuterohydroxylammonium ions to better than 2% and all 18 frequencies to better than 5%. The low NH and OH frequencies are believed to be due to the formal positive charge being distributed over all the atoms in the ion thereby weakening the covalently bonded H atoms and increasing the strengths of the electrostatic hydrogen bonds.
Separation of Boron Isotopes. III. The n-Butyl Sulfide-BF3 System
Authors: Palko A. A.
Published: January 2005

The gas-liquid isotopic exchange between BF3 and the n-butyl sulfide-BF3 complex was studied as a possible system for enriching boron isotopes. The single stage separation factor varied from 1.054 at —20°C to 1.033 at 26°C. B10 concentrated in the liquid phase. The heat of association of the n-butyl sulfide-boron trifluoride complex was determined to be —12.76±0.06 kcal/mole from a series of vapor pressure measurements of the complex made at several mole ratios of BF3 to sulfide.
Infrared Spectra of Alkoxyboranes. IV. Di- and Triisopropoxyboranes
Authors: Lehmann W. J. , Weiss H. G. , Shapiro I.
Published: January 2005

Frequency assignments are made, based on the infrared spectra of gaseous di- and triisopropoxyboranes. Correlation with spectra of other alkoxyboranes shows that the BO3 asymmetric stretching frequency is higher than the value previously assigned in the literature. Identification of the C–O stretching frequency in the 1050-1150 cm—1 range supports the interpretation that this region (rather than ca 1300 cm—1) represents the C–O vibration in alcohols.
Oxygen Isotope Fractionation in the System Calcium Carbonate-Water
Authors: Clayton Robert N.
Published: January 2005

The oxygen isotope exchange reaction between water and calcium carbonate has been studied over the temperature range 190°C to 750°C. Equilibrium constants for the reaction have been measured and fit the equation: lnK=2725T−2for all temperatures above 0°C. The implications to geological thermometry are discussed.
United Atom Treatment of the Behavior of Potential Energy Surfaces of Polyatomic Molecules at Small Internuclear Distances
Authors: Bingel Werner A.
Published: January 2005

It is shown that the potential energy function of any state of a polyatomic molecule can be expanded for small internuclear distances in the form V= ∑ ∑ α>βZαZβ/Rαβ+Wu+ ∑ α(E2α·Rα2+E3α·Rα3+···),where Wu is the energy of the particular state u of the united atom (UA) to which the molecular state in question connects, and Rα is the distance of the αth nucleus from the UA. Explicit expressions for the coefficients E2α, E3α are given in terms of the electronic charge density of the UA. The derived energy expansion is applied to the molecules CH4, NH3, H2O, and HF which all correspond to the united atom Ne.
Relationship of the Contact Angle to Interfacial Energies
Authors: McNutt James E. , Andes George M.
Published: January 2005

The commonly used relation between the contact angle and the specific free energies of three surfaces meeting at a line is correct, although it has been criticized in recent years. A rigorous derivation of the kind applicable to systems which can be analytically described is presented in detail. The completely general derivation of Gibbs is also reviewed. The kinds of errors in the derivations found in many texts are discussed.
Approximate Natural Spin Orbitals for the Hydrogen Molecule
Authors: Eliason Morton A. , Hirschfelder Joseph O.
Published: January 2005

Approximate natural spin orbitals and the corresponding occupation numbers are obtained over a wide range of internuclear separations for the Σg+1 ground state and the Σu+3 excited state of the hydrogen molecule, using the Hirschfelder-Linnett wave functions. The resulting natural expansions and their variation with internuclear separation are then discussed in terms of electronic configurations.