bluuebunny/crossref_metadata_2025 huggingface dataset:
Photochemical Studies in Flash Photolysis. III. Photolysis of Acetone in Different Wavelength Regions
Authors: Shilman A. , Marcus R. A.
Published: January 2005

The flash photolysis of acetone was studied at wavelength regions centered around 260, 280, and 300 mμ, using absorbed intensities of the order of 1019 quanta/cc/sec for each wavelength region. The light source was an exploding wire, and the maximum temperature increase per flash was calculated to be not more than 5°C. The products, analyzed by gas chromatography using a sensitive electric discharge detector, consisted of C2H6, CO, biacetyl, and, in smaller amounts, CH4. A search was made for other products as well, and detection limits are given.

The C2H6/CO ratio decreased with increasing acetone pressure at all wavelength regions and was independent of light intensity in the range investigated. The RCO/pacet ratio, measured over a wide pressure range, was pressure-independent at 260 and 300 mμ but increased appreciably with pressure at 280 mμ. At low pressures, where the C2H6/CO ratio approached a limiting value, the ratio decreased with wavelength according to the order 280>260>300 mμ.

The lifetime of the excited acetone molecules at the respective wavelengths was estimated, from a steady-state treatment, to be 0.6×10—9, 1×10—9, and 4×10—9 sec at 260, 280, and 300 mμ, assuming a collision deactivation efficiency of unity. At 300 mμ there was a marked difference in value of C2H6/CO at flash and low intensities: certain second-order reactions involving excited states appear to occur completely at the relatively high concentrations prevailing under flash conditions. The transition region of intensity effects is described in subsequent papers of this series.
Paramagnetic Resonance of Nitrogen Atoms in X-Ray-Irradiated Sodium Azide
Authors: Carlson Frederick F.
Published: January 2005

Electron paramagnetic resonance studies of the fine structure of nitrogen atoms trapped in x-ray-irradiated sodium azide at low temperatures have revealed that the atoms are trapped interstitially. There are three similar sites with magnetic axes parallel to the three axes of the rhombohedral unit cell. The data are fitted to an appropriate spin Hamiltonian, and the temperature dependence of the fine-structure parameters is discussed.
Free Energy of a System with Random Elements
Authors: Mazo Robert M.
Published: January 2005

It is shown that the free energy of a system containing random elements, whose distribution is subject to some fixed probability law, is given by the expectation value of the logarithm of the partition function, considered as a random variable.
Determination of Barrier Heights from Low-Temperature Heat-Capacity Data
Authors: Wulff Claus A.
Published: January 2005

A method is presented by which barrier heights, in potential functions hindering the internal rotation of methyl groups, or spectroscopically inactive vibrational frequencies, can be obtained solely from thermal data for the solid phase. The observed heat capacities are analyzed in terms of contributions from the lattice vibrations, the internal vibrations, the expansion of the lattice, and the internal rotation. At low temperatures, the hindered rotation can be treated as torsional oscillation with a frequency related to the barrier height. It is shown that barrier heights derived by this method are in accord with those estimated from comparison of gas-phase entropies, but can be determined with greater precision than such values.
NMR Studies of Hydrated Sodium Tetraborate Minerals. II. Na23 Sites in Borax and Tincalconite
Authors: Cuthbert J. D. , Petch H. E.
Published: January 2005

The quadrupolar splitting of the Na23 nuclear magnetic resonance signal has been studied in single crystals of borax, Na2B4O7·10H2O, and tincalconite, Na2B4O7·5H2O, placed in magnetic fields of 7536 and 5645 G, respectively. The resonance spectra show that the sodium atoms in both minerals occupy special positions with two unique sites in borax and three in tincalconite. The electric quadrupole coupling constants eqQ/h and asymmetry parameters η at these sites were determined to be BoraxTincalconiteWyckoff positionaed or eca or beqQ/h (kc/sec)541±3849±4539±2785±21299±1η0.449±0.0150.143±0.0280.741±0.00500The orientations of the principal axes of the electric field gradient tensors for the above sites and their symmetry-related sites have also been determined.
Short-Duration Visible Afterglow in Helium
Authors: Schmeltekopf Arthur L. , Broida H. P.
Published: January 2005

A bright, reproducible afterglow which consists of helium atomic and molecular emissions has been observed in the flow products of an electrical discharge in a DeLaval nozzle clearly separated from the discharge. This afterglow has been observed at pressures from 0.4 to 20 mm Hg and with flows from 10 to 1000 cm3/sec NTP. At the low pressure the existence of the afterglow is extremely pressure sensitive to small changes in pressure. Metastable He-atom concentration decreases after the discharge and then increases in the region of afterglow emission. The afterglow is very sensitive to impurities greater than a few parts in 105 and emission intensity is reduced by the presence of an rf field, possibly because heating the electrons retards recombination.
Numerical Solutions of the Convolution-Hypernetted Chain Integral Equation for the Pair Correlation Function of a Fluid. II. The Hard-Sphere Potential
Authors: Klein Max
Published: January 2005

The nonlinear integral equation of the hypernetted chain (HNC) approximation is solved for a fluid of hard spheres. An inconsistency introduced by the approximation results in a disagreement between two forms of the equation of state. The resulting pair of equations of state are compared with each other, with those obtained for the Born—Green and (approximate) Kirkwood equations by Kirkwood, Maun, and Alder, and with a reference isotherm made up of a combination of the five-term virial series at low and intermediate densities and the gas-like isotherm of molecular dynamics at high densities. The HNC equations of state are found to be a considerable improvement over those of the Born—Green and Kirkwood theories. At intermediate and high densities, the two HNC isotherms bracket the reference isotherm, their mean being a very good approximation to it. The HNC equation exhibits a tendency toward a gas—solid phase transition at extremely high densities. A transition is not actually predicted, however.
Cross Sections of Ion—Permanent-Dipole Reactions by Mass Spectrometry
Authors: Moran Thomas F. , Hamill William H.
Published: January 2005

Proton transfer is the most probable type of reaction observed in a number of ion—molecule interactions involving permanent dipoles. Integrated cross sections, which are unusually large, are described in terms of an ion—dipole pair oriented near the position of minimum energy at low relative velocity. As the relative velocity is increased, this alignment becomes less likely. The energy-dependent cross section is eclipsed at high relative velocity by the ``hard'' cross section which does not vary with energy. Proton affinities are estimated for several alkyl cyanides. Some of the reported reactions appear to involve excited states of the primary ions.
Do the ``Ligand Field'' Parameters in Lanthanides Represent Weak Covalent Bonding?
Authors: Jo/rgensen Chr. Klixbüll , Pappalardo Romano , Schmidtke Hans-Herbert
Published: January 2005

Instead of explaining the seven different f-orbital energies or five different d-orbital energies by parameters Anm〈rn〉 of the electrostatic ligand field model, we propose to classify the energy levels according to the actual one-electron energies and to interpret these quantities by the weak effects of σ antibonding on the partly filled shell. Calculations of the relative angular dependence Ξ2 of such effects are made in a simple model and compared with experimental data for nine- and eight-coordinated lanthanide compounds. The agreement is judged to be much more satisfactory than when the electrostatic model is applied, and the number of freely chosen parameters is much smaller.
Nonadiabatic Effects in the High-Energy Scattering of Normal Helium Atoms
Authors: Thorson Walter R.
Published: January 2005

There is a large discrepancy (∼9 eV) between the calculated adiabatic electronic energy of the ground state (X 1Σg+) of the system He2 and the effective scattering potential deduced from experiments with high-energy (2 keV) atomic beams, at small interatomic distances (R=0.53 Å). It is shown that at least a significant part (25%) of this discrepancy arises from nonadiabatic effects of high relative angular velocity of the atoms in the collisions typical of the experiment. A perturbation-theory treatment is included to give an estimate of the over-all magnitude of the effect; but a variational calculation is employed with the nonadiabatic Hamiltonian to produce the minimum estimates of nonadiabatic energy shifts to which we refer above. The theory correctly predicts the observed approximate agreement between adiabatic energies and the experimental potentials at larger distances (R=1.06 Å). A method of extending the variational calculation to include continuum contributions is described; it employs a pseudo-Hamiltonian to simplify the calculation. Arguments connected with this formulation are advanced to suggest that when continuum contributions are taken into account it may be possible to account for all or most of the observed discrepancy.
Destruction of Acetylene in Flames with Oxygen
Authors: Fenimore C. P. , Jones G. W.
Published: January 2005

The rate of consumption of acetylene in premixed flames is compared with the simultaneous rates of disappearance of oxygen, supposed to react by H+O2⇄OH+O, and appearance of carbon dioxide, OH+CO→CO2+H. The comparisons are consistent with a consumption of acetylene by O atoms but not by H, OH, or O2. The destruction probably involves a direct attack of O on carbon in acetylene with a rate constant of 1 to 2×1013 cm3 mole—1 sec—1 and little temperature dependence.
Molecular and Crystal Structure of C2H5NH2B8H11NHC2H5
Authors: Lewin Ruth , Simpson Paul G. , Lipscomb William N.
Published: January 2005

A three-dimensional x-ray diffraction study has yielded the complete molecular structure of EtNH2B8H11NHEt, which is the first reported derivative of a B8 fragment of the icosahedral boron arrangement. The EtNH2 ligand is attached by a single bond, but the NHEt group is in a bridge position between two B atoms in an arrangement known previously only in B2H5NR2 where R is H or alkyl. There are four molecules in a monoclinic unit cell having symmetry P21/a, and having parameters a=24.35, b=5.98, c=9.00 Å, and β=94°50′.
High-Temperature Heat Content of Niobium Carbide and of Tantalum Carbide
Authors: Levinson L. S.
Published: January 2005

The heat content of niobium carbide was measured between 1289° and 2778°K and that of tantalum carbide between 1296° and 2843°K using a drop calorimeter.
Electronic Wavefunction for the Ground State of Methane
Authors: Sinai John J.
Published: January 2005

A single determinant wavefunction for the ground state of the methane molecule is constructed from molecular orbitals which are expressed as linear combinations of Slater orbitals centered on the carbon and hydrogen nuclei. The coefficients of the atomic orbitals in these expansions are determined by the LCAO—SCF procedure. The total molecular energy obtained is —39.86 a.u. The electronic charge density is plotted in a plane containing the carbon nucleus and two hydrogen nuclei.
Polarization of the π*→π and π*→n Phosphorescence Spectra of N-Heterocyclics
Authors: El-Sayed M. A. , Brewer R. G.
Published: January 2005

Phosphorescence polarization measurements have been performed by the method of photoselection. Since this technique requires a knowledge of the polarization of at least two perpendicularly polarized absorption bands, the method can be fully exploited in the case of the N-heterocyclics where the (n, π*) and (π, π*) absorptions are perpendicular to each other. The results on pyrazine (1,4-diazabenzene) show that the π*→n emission is polarized along the N···N axis, in agreement with previous work. The polarization is uniform throughout the 600-cm—1[ν6(ag)] progression and does not alternate as does the intensity and the vibrational frequency. This behavior might arise from a resonance-type interaction which produces a progression with mixed Franck—Condon characteristics. Quinoxaline (1,4-diazanaphthalene) is found to have a π*→π phosphorescence spectrum which is highly polarized out of the plane. Approximate calculations show that the (n, π*) singlet state in quinoxaline is at least as important as the (σ, π*) states in mixing with the emitting (π, π*) triplet state. The general conclusion is reached that in nitrogen heterocyclics when the phosphorescent state is of the (n, π*) type, the mixing singlet is of the (π, π*) type, or in-plane Rydberg state, whereas if the emitting triplet state is of the (π, π*) type, the mixing singlet might be of the (n, π*), (σ, π*) and/or perpendicularly polarized Rydberg state.
First-Order Phase Transition in a Gas of Long Thin Rods
Authors: Zwanzig Robert
Published: January 2005

Onsager's prediction of a first-order phase transition in a gas of long thin rods is verified by extensive calculations on a simple model. The molecules are rectangular parallelepipeds, of length l and square cross section d×d. The long molecular axes can point in only three mutually perpendicular directions. Virial coefficients, up to the seventh, are calculated exactly as functions of orientation, in the limit l→ ∞, d→0, and l2d=constant. The transition predicted by Onsager's theory, based on a second virial approximation to the potential of mean force in the space of relative orientations, is observed also when all virial coefficients up to the seventh are included. The virial expansion appears to converge well for the isotropic phase; but the properties of the anisotropic phase depend sensitively on the order of approximation.
SPO (Split-p-Orbital) Method. IV. Calculations for the (2p)2 State of Helium
Authors: Dewar Michael J. S. , Chung Alice L. H.
Published: January 2005

The energies of the three possible (2p)2 states of helium (1S, 1D, 3P) are calculated with SPO functions and with correlated Hylleraas functions. Calculations are also carried out for the nonstationary (2pz)2 state. The results indicate that vertical correlation is an important factor in systems containing p electrons.
Rotational Correlation Times for Quadrupolar Relaxation in Liquids
Authors: O'Reilly D. E. , Schacher G. E.
Published: January 2005

The nuclear spin relaxation rate via quadrupolar interaction in liquids is related to the correlation time for rotational Brownian motion. Experimentally obtained values of the Cl35 relaxation times at various temperatures in chlorine-containing molecules are used to calculate the correlation times for these molecules. The values so obtained are an order of magnitude shorter than predicted by the familiar Stokes—Einstein relation. An expression for the rotational correlation time is derived using the liquid ``quasilattice'' model, assuming that relaxation takes place only when the molecule undergoes a ``jump'' to the top of the barrier at the cell boundary. Using this theory the correlation time for CCl4 is calculated and is in good agreement with the experimental value.
Kinetics of Three-Body Atom Recombination
Authors: Kretschmer C. B. , Petersen H. L.
Published: January 2005

The following values of the three-body recombination rate constant in units of cc2/mole2 sec were measured at 300° or 350°K: N+N+N2→N2+N2,8.0×1014,N+O+N2→NO+N2,3.3×1015,H+H+H2→H2+H2,8.9×1015.The rate constant for the reaction N+O2→NO+O was found to be 5×107 cc/mole sec at 350°K. A statistical-mechanical calculation of the three-body recombination rate constant gave values which agreed well with the above experimental results and also reproduced the previously determined value of <2.5×1014 cc2/mole2 sec for O+O+O2→O2+O2. The large variation in rate constant for different gases is due mainly to differences in atomic masses and statistical weights. Redissociation of molecules in high vibrational levels is important in reducing the net rate of recombination. At high temperatures, the theory predicts a rate constant varying as T—1.
Infrared Spectra of Highly Associated Liquids and the Question of Complex Ions in Fused Salts
Authors: Wilmshurst J. K.
Published: January 2005

Infrared absorption spectra have been derived from infrared reflectivity data by the method of Robinson and Price for the systems LiNO3–NaNO3, KNO3–AgNO3, LiNO3–LiOH, LiNO3–H2O, LiClO3–H2O, LiOH–NaOH, ZnCl2–LiCl, ZnCl2–KCl, CuCl2–LiCl, CuCl2–KCl, and CuCl–LiCl. The question of the determination of the existence and nature of complex ions and ion-pairs in these strongly associated systems has been critically discussed and operational criteria have been suggested. In only one system studied (CuCl2–KCl) was the presence of a complex ion indicated by the spectroscopic data.
Vibrational Relaxation of Oxygen
Authors: White Donald R. , Millikan Roger C.
Published: January 2005

The vibrational relaxation of oxygen has been studied by shock-tube interferometry from 600° to 2600°K with the result that at 1 atm pressure the relaxation time τv in seconds is found to be τv=1.49×10—10 exp (133T—½). The presence of up to 2% CO has no observable effect on this time. The previous experimental work of Blackman was probably influenced by impurities at the lower temperatures but the present results are in accord with his at the higher temperatures. Comparison is made with various theoretical calculations and the primary temperature dependence of T—½ is confirmed. It is further noted that Schwartz's Method A of matching the exponential interaction is in better accord with observations than Method B.
Oxygen Vibrational Relaxation in O2–He and O2–Ar Mixtures
Authors: White Donald R. , Millikan Roger C.
Published: January 2005

The vibrational relaxation time of oxygen in several mixtures of O2+He and O2+Ar has been determined by shock-tube interferometry. Using the previously determined data for O2–O2 collisions, the vibrational relaxation time for O2–He and O2–Ar collisions has been found. The latter is in agreement with Camac's determination and extends to somewhat lower temperatures. For oxygen infinitely dilute in helium, the vibrational relaxation time in atm·sec is given by pτv=5.3×10—9 exp(60T—½) from 400° to 1600°K.
Rotational Dependency of the Stark Effect of a Polar Diatomic Molecule
Authors: Wharton L. , Klemperer W.
Published: January 2005

The calculation of the Stark effect of a rigid polar 1Σ diatomic molecule neglects the effects of (1) the vibrational and electronic structures (2) the rotation—vibration interaction that contribute to the quadratic Stark effect. In this paper it is shown that the two effects have slightly different rotational dependency. The vibrational and electronic structures contribute a (cosine)2 term that can be viewed as an anisotropy of polarizability, while the vibration—rotation interaction gives a similar, but distinct variation with rotational quantum numbers.
Infrared Spectra in Polarized Light of Acenaphthene Crystals and Assignment of Molecular Vibrations
Authors: Colombo L.
Published: January 2005

Infrared spectra of acenaphthene crystals measured with polarized radiation in the region 400–3000 cm—1 are reported. The unit cell contains four molecules. Splitting of bands in the crystal spectrum has been observed. However, because of the specific positions of molecules in the crystal lattice, a unique determination of the vibration symmetry is possible. An assignment of recorded frequencies is proposed.
Microwave Spectrum, Quadrupolar Coupling Constants, and Dipole Moment of Chlorobenzene
Authors: Poynter Robert L.
Published: January 2005

The microwave spectrum of chlorobenzene has been observed in the frequency range between 8000 and 30 000 Mc/sec. An analysis of this spectrum gives the following values for the rotational constants for the two isotopic species, C6H5Cl35 and C6H5Cl37; A=5672.951 Mc/sec, B=1576.774 Mc/sec, C=1233.672 Mc/sec for the Cl35 isotopic species and A=5672.530 Mc/sec, B=1532.790 Mc/sec, C=1206.571 Mc/sec for the Cl37 isotopic species. The quadrupolar coupling constants which were obtained from the quadrupolar hyperfine structure are eqQ=—71.10 Mc/sec for Cl35 and eqQ=—56.10 Mc/sec for the Cl37. The quadrupolar asymmetry parameter η cannot be determined from the microwave spectrum. The observed dipole moment is 1.78±0.06 D.
Vector Methods in the Theory of Molecular Vibrations
Authors: Cyvin B. N. , Cyvin S. J. , Kristiansen L. A.
Published: January 2005

Some comments are given on the construction of Polo's ρ vectors. Methods are reported for the construction of the (a) G—1Cα and (b) G—1CαG—1 matrices by means of the (a) ρ and s vectors, and (b) ρ vectors alone. These matrices are important in the study of Coriolis interaction coefficients of rotation—vibration. For illustration of the theory the ethylene-type molecular model is taken as an example.
Influence of an Electric Field on the Dielectric Loss of the Liquid Crystal p-Azoxyanisole
Authors: Carr E. F.
Published: January 2005

This work involves the alignment of molecules in the anisotropic liquid phase of p-azoxyanisole due to externally applied dc and ac electric fields and walls of the sample holder. Microwave techniques involving dielectric measurements are used to provide a measure of the alignment. Results are discussed which suggest that for very pure samples an alignment should be produced with the long axes of the molecules perpendicular to the externally applied electric field. The alignment with the long axes parallel to the external field which is often observed appears to be due to an extremely small amount of impurity. This alignment appears to be associated with the conductivity, with an alignment produced such that the conductivity is a maximum in the direction of the field. Results are also discussed which suggest that small amounts of impurity are effective in producing an alignment of the molecules parallel to the walls of the sample holder.
Diffusion and Heterogeneous Reaction. V. Transition from a Surface- to a Diffusion-Controlled Process during Atom Recombination
Authors: Wise Henry , Ablow Clarence M. , Schott Dan J.
Published: January 2005

The limiting conditions are examined under which the kinematics of diffusion or the kinetics of reaction predominate. Consideration is given to a system in which homogeneous and heterogeneous reactions occur with and without convective flow. Experimental measurements of hydrogen atom recombination on catalytic surfaces, as a function of total gas pressure, are interpreted in terms of surface- and diffusion-controlled processes.
Irreducible Cluster Integrals of Hard-Sphere Gases
Authors: Katsura Shigetoshi , Abe Yutaka
Published: January 2005

Three different methods of computing irreducible cluster integrals of hard-sphere gases are developed and discussed. The first one employs integration in configuration space. The second one involves the multiple summation of infinite series of Weber—Schafheitlin-type integrals. The third one is an extension of Nijboer—van Hove's modified Fourier transformation method. Of values of components of the fifth virial coefficient, Nos. 1, 2, 3, 4 have been obtained by the first method; Nos. 2, 5, 6, 7, 8 by the second method; and Nos. 1–10 also by a Monte Carlo method. The value of E/b4 is 0.1097. The value of the fifth virial coefficient for square-mound potential has also been given.
``Smoothed Potential'' Theory of Chemical Binding
Authors: Arnold James R.
Published: January 2005

A simple model, similar to the ``free electron'' theory of metals and conjugated systems, is shown to yield good values for the energies of most single covalent bonds. The model can be extended to multiple bonds and charged species, but not in its present form to excited states and unstable species. It can be correlated with the free electron theory of metals.

The significance of the success of this and other simple models in predicting bond energies is discussed.
Vibration Spectra of Some Mixed Halides of Boron
Authors: Lindeman Louis P. , Wilson M. Kent
Published: January 2005

Mixed halides of boron have been shown to exist in binary mixtures of the trihalides. Most of the fundamental frequencies of BF2Cl, BFCl2, BF2Br, BFBr2, BCl2Br, and BClBr2 for molecules containing boron-10 and boron-11 have been observed and assigned to the proper modes of vibration. With the aid of the trihalide frequencies a normal coordinate treatment has been made for the mixed halides. Some discussion of the validity of transferring force constants in this system has been given.
Ultraviolet and Infrared Absorption Spectra of Substituted Acetophenones and Benzoic Acids
Authors: Tanaka Jiro , Nagakura Saburo , Kobayashi Michio
Published: January 2005

Influences of substituents on the ultraviolet and infrared absorptions of acetophenone and benzoic acid are investigated from theoretical and experimental points of view. In the present paper, all theoretical considerations are made by the molecular energy-level diagram method developed by the authors.

Ultraviolet absorption spectra of some substituted acetophenones are measured in n-heptane, alcohol, water, and sulfuric acid. It is found that most molecules studied here have absorption bands corresponding to the n→π* transition of the carbonyl group, A1g→B2u and A1g→B1u transition of the benzene ring, and intramolecular charge-transfer absorption. Especially concerning last absorption, a somewhat quantitative theoretical consideration is presented and satisfactory agreement is obtained between the theoretical and observed excitation energies.

Infrared absorption spectra of carbonyl groups in substituted acetophenones are measured in carbon tetrachloride. The observed carbonyl frequencies are compared with the bond orders of this bond calculated on the basis of the above method. Good correlation is also found between these two quantities. A similar consideration is also made with substituted benzoic acids.
Chain Model for Polyelectrolytes. IV. Skeletal Distribution Effects in Equimolar Polyampholytes
Authors: Harris Frank E. , Rice Stuart A.
Published: January 2005

The chain model for polyelectrolytes developed in the preceding papers of this series is extended to equimolar polyampholytes of general skeletal structure. The present development differs from that for copolymers consisting of a regular alternation of acidic and basic groups in that the environments of the individual groups will depend upon the local skeletal distribution. This inhomogeniety affects both the titration and configurational properties, primarily through a displacement of the acid-base equilibria. In addition, locally inhomogeneous skeletal structure can cause either an expansion or contraction at the isoelectric point, although strong deviation from random copolymerization is necessary to realize a large effect. No experimental data are available with which to compare the theory, but a calculated titration curve and expansion ratio are presented for a hypothetical polyampholyte of random skeletal structure. It is found that the titration curve of the random copolymer exhibits more buffer action near the isoelectric point than does a similar regularly alternating copolymer, but that the configurational properties and the effect on the titration curve of increased ionic strength are quite similar to the corresponding effect for the regularly alternating copolymer. It is pointed out that substantial change in titration properties may be realized by alterations in the skeletal structure of a copolymer.
Note on the Theory of Diffusion Controlled Reactions : Application to Photodissociation in Solution
Authors: Monchick Louis
Published: January 2005

The theory of diffusion controlled reactions has been reconsidered in the light of modern transport theory, and it has been concluded that the use of the Smoluchowski equation is valid for most problems of usual interest. The probability of reaction has been calculated for two molecules initially separated by a distance r′, in the presence of a third reactant present in uniform concentration. The resulting formulas have been used to discuss the quantum yields of photodissociation of Br2, Br3—, and I3— in aqueous solution. The dependence on temperature and wavelength can be qualitatively accounted for.
Pressure Coefficient of the Dielectric Constant of Water
Authors: Mavroides John G.
Published: January 2005

Theoretical calculations of the pressure coefficient of the dielectric constant of water have been made based on the following models: (a) water molecules considered as tetrahedrally packed (one-state model) and (b) water molecules considered as packed in two ways: tetrahedrally and simple close-packed (two-state model). These calculations are compared with experiment.

The pressure coefficient has been measured by a newly derived dynamic method in which the pressure is applied ultrasonically. The measurement compares favorably with previously published values which were obtained with static pressures.
Nitric Oxide Fundamental
Authors: Shaw J. H.
Published: January 2005

The 5.3μ rotation-vibration band of NO has been re-examined with a high resolution spectrometer. A set of constants has been determined which is in good agreement with existing data.
On the Coupling between Electronic and Nuclear Motion and Van der Waals' Interaction between Helium Atoms
Authors: Wu Ta-You
Published: January 2005

The analytical expression for the potential due to the coupling between the electronic and the nuclear motion for two normal helium atoms has been obtained for a wave function of the form of that of P. Rosen. This coupling interaction is a repulsive potential and is to be added to the usual ``valence'' and Van der Waals' potential obtained in the static-nuclei approximation. This coupling interaction, being inversely proportional to the reduced mass of the two interacting atoms, contributes to a weaker binding between two He3 atoms than between two He4 atoms.
Molecular Orbital Approximation to Electron Coupled Interaction between Nuclear Spins
Authors: McConnell H. M.
Published: January 2005

The general formulas obtained by Ramsey for the indirect second-order magnetic coupling of nuclear spins by electron spin and orbital magnetic moments in 1Σ molecules are used together with an antisymmetrized product of molecular spin orbitals to obtain a set of general equations for nuclear spin couplings which only involve (a) the individual molecular orbitals, and (b) rotationally invariant one and two electron space operators. By approximating the molecular orbitals with linear combinations of atomic orbitals quite tractable formulas are obtained for ``long-range'' nuclear spin-spin couplings, i.e., couplings between nuclei separated by two, three, or more bond lengths. The application of these formulas are illustrated by the development of an approximate formula for proton-proton coupling constants in terms of interproton bond orders, the application of this formula to methane, as well as some qualitative considerations of F19—F19 coupling constants in tetrafluoroethylene. In general nuclear spin couplings between protons not directly bonded to one another arises primarily through hyperfine interactions between protons and pairs of electron spins. In hydrocarbons long-range bond orders between protons, ηHH′, can be estimated from observed proton spin couplings by the equation, ηHH′2 = 0.5 × 10—2 JHH′ (in sec—1). In fluorocarbons (and probably many other substances) nuclear couplings are due to the combined effects of hyperfine electron orbital and electron spin interactions with F19 nuclei. Electron exchange effects are important for both two-electron spin and orbital contributions to nuclear coupling.
Effect of Pressure on the Frequency of the O–H Band in Butanol Solutions
Authors: Fishman Erwin , Drickamer H. G.
Published: January 2005

The infrared spectra of dilute solutions of normal butanol have been observed in the 3-micron region at pressures from 10 to 12 000 atmospheres. The sharp ``monomeric'' O–H band shifts toward lower frequencies as the pressure increases. If we define Δv as the shift in frequency from its value at one atmosphere and 25°C in each solvent, Δv at the maximum pressure varies from 11 cm-1 in 2, 3 dimethyl butane to 41 cm-1 in n-propyl iodide. The frequency shift is found to be a linear function of the square of the density and the polarizability of solvent bonds, though this latter relationship is not quantitative. The shifts are plausibly explained as due to van der Waals' forces between the O–H bond and the solvent. The pressure causes a large increase in the polymerization of the alcohol, from which the change of volume on polymerization is estimated to be —4.64 cm3/mole in the 1 to 5820 atmosphere range, and —2.47 cm3/mole in the 5820 to 11 330 atmosphere range.
Misassignment of the Multiplicity Forbidden Transitions in Pyridine
Authors: Brealey Graham J.
Published: January 2005

Experimental work is described which indicates that the two previously assigned singlet-triplet transitions for pyridine, in the regions 29 000—33 000 cm—1 and 25 000 — 28 500 cm—1 are due to impurities. The higher energy absorption is shown to be due to an impurity of pyrazine in pyridine to the extent of 1 part in 150 000. This pyrazine impurity is shown to be responsible also for causing the apparent phosphorescence emission of pyridine in the region 26 600 to 20 000 cm—1.
Confirmation of the Anomalous Fluorescence of Azulene
Authors: Viswanath Gorthi , Kasha Michael
Published: January 2005

The light emission properties of the azulene molecule and several alkyl-substituted azulenes have been studied. In confirmation of recent results of Beer and Longuet-Higgins, it is found that anomalous (S″→S) fluorescence occurs in azulene, with v̄max at 26 802 cm—1 (rigid glass solution in EPA at 77°K). Red-shifts for this fluorescence are found in several alkyl-substituted azulenes, in qualitative agreement with substitution theory. The absence of normal (S′→S) fluorescence and the absence of any phosphorescence (T→S) emission to 11 000 A, the apparatus limit, are also confirmed. The emission observations are discussed, and alternative interpretations are given.
Analysis of the Near Ultraviolet Absorption Spectrum of 1,2,4,5-Tetrachlorobenzene Vapor
Authors: Matubara Ikuo , Anno Tosinobu
Published: January 2005

The absorption spectrum of the 1,2,4,5-tetrachlorobenzene vapor lying in the wavelength region between 3040 and 2650 A was photographed and measured. The band at 34 149 cm—1 is assigned as the 0,0 band. The progression with frequency intervals of 1134 cm—1 starts from the stronger bands. Most of the prominent bands are assigned to progressions or combinations of the possible fundamental frequencies. The fundamental frequencies are compared with the Raman values. A tentative assignment of the fundamental frequencies is discussed. The change of the molecular structure in the course of the electronic transition is also discussed.
Isotherms in the Critical Regions of Carbon Dioxide and Sulfur Hexafluoride
Authors: Wentorf R. H.
Published: January 2005

The p-v isotherms of carbon dioxide and sulfur hexafluoride have been measured in their critical regions at 0.02°C temperature intervals while the gases were observed and photographed. It was found that the liquid-vapor boundary curve has a nearly flat top; this renders the classical van der Waals picture of the critical region inadequate. Some slight evidence was found for an anomalous critical region as predicted by Mayer, but this region could be only 0.04°C high for sulfur hexafluoride and less than 0.02°C high for carbon dioxide. It was found that constant pressure is rapidly achieved in the critical region, but that constancy of fluid structure requires five or more hours. The results of these experiments agree well with those of MacCormack and Schneider for sulfur hexafluoride and those of Michels for carbon dioxide. The influence of gravity upon critical phenomena was found to be large. A brief discussion of its effects and corrections to be made on account of it are given.
Method for the Determination of the Surface Tension of Solids, from Their Melting Points in Thin Wedges
Authors: Sill Richard C. , Skapski Adam S.
Published: January 2005

A method is proposed which allows one to measure the surface tension of solids whose liquids wet glass and steel and whose solid/liquid contact angle against those materials is zero.

A thin wedge, formed of optically flat steel and glass slabs, is filled with liquid substance and then allowed to solidify. It is then immersed in a large heat bath whose temperature is raised at a rate of about 1.5°C per 24 hours, and is known at any time within ±0.002°C. The solid substance starts melting from the thinnest part of the wedge, well below its ``normal'' melting point Tm. From the lowering of the melting point ΔT corresponding to a measured thickness h of the wedge in the solid/liquid interface, the surface tension of the solid σS is then arrived at from the equation: σS=QfρS2TmhΔT+σL,where Qf is the heat of fusion in erg/g, ρS the density of the solid, and σL the surface tension of the substance in liquid state.

The method was applied to stearic and myristic acids. For myristic acid four independent measurements gave an average value of σS=116±10 erg/cm2, all four samples showing similar orientation of the crystal lamellae (gross crystal orientation) with respect to the interface solid/liquid. For stearic acid three similar gross orientations gave an average σS=179±8 erg/cm2. One gross orientation, markedly different from the others, yielded the value of σS=135±6 erg/cm2.

Thickness h was determined from the interference lines (sodium light). The gross orientation was observed in polarized sodium light.
Nuclear Magnetic Relaxation of Nonuniform Systems
Authors: Broersma S.
Published: January 2005

The effect of electric ions in water upon the proton magnetic relaxation is discussed. Formulas pertaining to solutions of paramagnetic and nonmagnetic ions are derived. The viscosity factor occurring in the theory for uniform systems has to be replaced by an average of inverse local viscosities weighted by the dimensions of the moving particles or by individual diffusion constants. The concept of mutual viscosity—describing the interaction between two unlike liquid layers—is helpful in correlating the numeric results.

The influence of temperature and concentration has been studied experimentally. The behavior of trivalent ions like aluminum can be understood by assuming hydration. The effect of monovalent ions can be explained on the basis of a slightly decreased diffusion constant of the free water molecules. Treated as a two-phase system, the experimental results enable the evaluation of the average time of adsorption. For aluminum, this is one-hundredth of a second.
Observations on Ion Separation in Dilute Solutions by Freezing
Authors: Lodge James P. , Baker Miriam L. , Pierrard John M.
Published: January 2005

The electrification produced by the freezing of dilute aqueous solutions was studied in an attempt to determine (1) the factors governing which ion is rejected by the ice phase, and (2) the interrelationship of concentration, freezing rate, observed potential, and ionic segregation between the phases for sodium chloride, which appears to be typical. It was shown that ionic rejection is not on the basis of ion size alone, though this is doubtless important. Ion segregation increases with freezing rate over the range studied. Observed interphase potential goes through a maximum as concentration is increased; at a given concentration, the potential also goes through a maximum as freezing rate increases. The freezing rate corresponding to this maximum potential is lowest in the vicinity of the concentration yielding the highest potential. The effects of concentration and freezing rate on the potential-time curves were also noted. Chemical analyses of the phases was complicated by self-electrolysis of the solution. Physical interpretations of some of these phenomena are offered.
Cell and Cell-Cluster Models for Liquids
Authors: Green H. S.
Published: January 2005

The theory of the cell model is developed in its most general form, allowing an arbitrary volume and a variable number of occupants to each cell. Kirkwood's principle of minimizing the free energy is used to determine the best cell distribution functions and thermodynamic functions. It is shown that the isotherms computed by Lennard-Jones and Devonshire are subject to two large but almost compensating corrections. It is proposed to eliminate the inconsistencies of the cell model by introducing de Boer's concept of cell clusters, which in principle allows an exact evaluation of the partition function. Numerical corrections for clusters of two cells are calculated and shown to be small in effect.
Self-Diffusion in Liquid Mercury
Authors: Nachtrieb Norman H. , Petit Jean
Published: January 2005

Self-diffusion in liquid mercury was determined by a shear cell method. At atmospheric pressure, D=8.5 × 10—5 exp(—1005/RT) cm2 sec—1 from 0° to 98°. At 30° for pressures ranging up to 8366 kg cm—2, log10D = —0.572Tm/T—4.348, or log10D=—4.7889—9.637×10—6P (kg cm—2). The activation volume is 0.587 cm3. The pressure dependences of viscosity and diffusivity are identical within experimental error, but the temperature variations are not equal. The results are discussed in terms of an imperfect crystal lattice model of a liquid.
Quadrupolar Splitting of the Al27 and Be9 Magnetic Resonances in Beryl Crystals
Authors: Brown L. Carlton , Williams Dudley
Published: January 2005

The quadrupolar hyperfine structure of the Al27 and Be9 nuclear magnetic resonance peaks in beryl crystal at 300°K have been examined. From the observed spectra, the following values were obtained for the nuclear spins I, the effective nuclear magnetic moments μ, the nuclear quadrupole coupling constants eQ[open phi]zz, and the electric field asymmetry parameters η: Al27:  I=5/2,  |μ|=3.6385±0.0003 n.m.,|eQ[open phi]zz|=3.093±0.015 Mc/sec,  η=0.000±0.005.Be9:  I=3/2,  |μ|=1.774±0.0002 n.m.,|eQ[open phi]zz|=0.504±0.004 Mc/sec,  η=0.090±0.005.
Magnetic Susceptibility Study of the Liquid Phase Equilibrium N2O4⇌2NO2 in Pure Nitrogen Tetroxide
Authors: Whittaker A. Greenville
Published: January 2005

The magnetic susceptibility of liquid nitrogen tetroxide was measured by the Gouy method over the temperature range 0°C to 30°C. The liquid was found to be diamagnetic throughout this temperature range although the diamagnetism decreased as the temperature increased. The magnetic measurements were found to be in good agreement with the spectrophotometrically determined equilibrium composition of the liquid as reported by Steese and Whittaker.
Dissociation Energy of Gaseous LaO
Authors: Chupka William A. , Inghram Mark G. , Porter Richard F.
Published: January 2005

The gaseous species in thermodynamic equilibrium with La(l) — La2O3(s) mixtures in the temperature range 1650°K to 1900°K have been studied mass spectrometrically. The major ions observed were La+ and LaO+. These ions were shown to be formed predominantly from La(g) and LaO(g), respectively. A thermodynamic treatment of ion currents yields a value of ΔH00=100±4 kcal/g atom for the heat of vaporization of La(s) and a value of ΔH00=189±8 kcal/mole for the reaction LaO(g)=La(g)+O(g) or D0(LaO)=8.15±0.35 ev.
Behavior of Liquid-Crystal Compounds Near the Isotropic-Anisotropic Transition
Authors: Hoyer W. A. , Nolle A. W.
Published: January 2005

The compressibility and the specific volume of liquid p-azoxyanisole are studied in the temperature range of the anisotropic-isotropic transition. Both quantities exhibit easily observable pretransitional variations in an interval extending more than two centrigrade degrees either side of the transition. The pretransitional behavior is largely consistent with the Frenkel theory of heterophase fluctuations, provided that an interfacial energy of approximately 0.3 erg/cm2 between phases is assumed, but the theory apparently does not apply to temperatures very near to the transition. The compressibility measurements were made by an ultrasonic pulsed-signal method, which also yielded the ultrasonic absorption for various frequencies from 0.5 to 6.0 Mc. Both the compressibility and the absorption have sharp maxima at the transition. Generally similar ultrasonic results were obtained with cholesteryl benzoate. The frequency dependence of the absorption in p-azoxyanisole corresponds approximately to a two-state compressional reaction with a relaxation time of the order of 10—8 sec, which is somewhat greater than the Debye characteristic molecular orientation time for the isotropic phase. Thus the controlling rate mechanism for the absorption is identified tentatively with the orientation time of molecules or of small clusters. The magnitude of the absorption is consistent with a model in which the relaxation effect is associated with the pretransitional increment in the compressibility.
Molecular Constants of Nitrous Oxide from Measurements of ν2 at 17μ
Authors: Lakshmi K. , Rao K. Narahari , Nielsen H. H.
Published: January 2005

The vibration-rotation absorption band of nitrous oxide associated with the fundamental bending vibration ν2 at 17μ was measured with a grating ruled with 2000 lines/in. and the molecular constants were determined. It was not possible to detect any change in the centrifugal stretching constants for the two states involved in the transition.
Thermodynamic Properties of Gaseous Zirconium
Authors: Kolsky Harwood G. , Gilles Paul W.
Published: January 2005

Tables of the thermodynamic properties of zirconium considered as an ideal monatomic gas were calculated using the Los Alamos Scientific Laboratory IBM 701 Computer for a temperature range 0 to 8000°K.
Shape Distribution of Two-Dimensional Soap Froths
Authors: Kikuchi Ryoichi
Published: January 2005

In the two-dimensional soap froths, made in the narrow space between two parallel glass plates, thin soap films partition the space into polygonal cells. The probability of occurrence of n-sided polygons (3 ≤n≤12) is calculated from two models, using the technique previously developed by the author for cooperative phenomena. The theory explains the observations semiquantitatively.
Solid Solutions of Ice and NH4F and Their Dielectric Properties
Authors: Zaromb Sol , Brill Rudolf
Published: January 2005

The solidus curve for the system H2O–NH4F was partly determined by means of chemical analyses, heating curves and a dilatometric method, and partly estimated from the liquidus curve using a thermodynamic relation. The solubility limit thus estimated is roughly 10%. The dielectric relaxation times, τ, of solid solutions of ice containing 0.002 to 10 weight percent NH4F were measured at temperatures of about —60° to —10°C. The activation energies for dipole rotation were only about 4 kcal/mole as compared with 13 kcal/mole in pure ice. At low concentrations the frequency factor increases with increasing concentration of NH4F. At high concentrations of NH4F this trend is reversed.
Vibrational Spectrum of Tetrabromoethylene
Authors: Mann D. E. , Meal J. H. , Plyler Earle K.
Published: January 2005

The infrared spectrum of C2Br4 in various solvents and as a liquid has been observed and measured in the range 3—100μ. The new data, in conjunction with earlier results and force constant calculations, have enabled for the first time an essentially complete and satisfactory vibrational assignment. The fundamentals, in units of cm—1, are 1535, 265, 144 in a1g; 880, 208 in b1g; 766, 119 in b2u; 635, 188 in b3u; 66 in a1u; 245 in b1u; and 464 in b2g. The present results for C2Br4 have required that two changes be made in the earlier assignment for C2Cl4. The angular modes of the chloro compound in b1u and b3u are now found to be at 288 and 310 cm—1, respectively. The assignments for C2F4, C2Cl4, and C2Br4 are then complete and concordant.