bluuebunny/crossref_metadata_2025 huggingface dataset:
Slow Pulse Modulation in Nuclear Magnetic Double Resonance. Indirect Determination of the NMR Parameters of 13C
Authors: Freeman R.
Published: January 2005

A new experimental technique is described whereby the weak 13C satellite lines of high-resolution proton magnetic resonance spectra are selectively detected and the remaining strong proton lines effectively suppressed, making possible the retrieval of previously obscured information about spin coupling between 13C and 1H. The detection system is sensitive only to those features of the proton spectrum that are perturbed by the application of a second rf field w2 near the 13C resonance frequency. The NMR signal is periodically inverted in synchronism with a 0.25-cps pulse modulation of w2, and integrated over at least one full period, by the use of the addition and subtraction modes of a time-averaging computer or low-frequency synchronous detector. Experimental evidence is presented that the proton magnetic resonance response to the modulation is quite rapid (rise time of the order of 0.7 sec) and is probably determined by magnetic field inhomogeneities and not by the 13C relaxation times. An analogy is drawn with the pulse experiments which were performed by Torrey in 1949. The technique has been extended to investigate 13C resonance spectra while benefitting from the much higher inherent sensitivity of proton magnetic resonance. The proton resonance frequency of one of the 13C satellites is continuously monitored while a pulse-modulated weak rf field is swept through the 13C region. Modulation is detected whenever w2 passes through a 13C transition that shares an energy level with the monitored proton line. In this way the 13C precessional frequencies of the carbonyl group in acetic acid and in acetone have been measured and related to the proton resonance frequency of tetramethylsilane in the same magnetic field with an accuracy of about ±2 parts in 108. These methods have been applied to the study of the inner 13C satellite spectrum and the 13C spectrum of 1,3,5-trichlorobenzene, and indicate that J(HH, meta), J(13CH) and J(13CCCH) all have like signs, a determination that has some bearing on the question of absolute signs of proton—proton spin coupling constants.
Study of Metal-Ion Binding to Nucleic Acids by 31P Nuclear Magnetic Resonance
Authors: Shulman R. G. , Sternlicht H. , Wyluda B. J.
Published: January 2005

We have measured the 31P NMR in aqueous solutions of RNA (ribonucleic acid) and AMP (adenosine monophosphate) containing Mn2+ and Co2+ ions. Measurements of T1, T2, and Δω, the shift from γIH0, were made as functions of the metal-ion concentration and the temperature. Near-room-temperature linewidths were determined by the slow chemical exchange. At higher temperatures the Co2+ complexes enter the exchange-narrowed region where 31P shifts in the CoAMP system are observed.

The room-temperature value of T1 for CoAMP and CoRNA complexes, the high-temperature shifts of the CoAMP, and the high-temperature values of T2 in the MnAMP all independently determine the strength of the isotropic transferred hyperfine coupling A between the metal ions and the 31P nuclei. Within the experimental accuracy which ranges from ∼5% (for Δω) to ∼50% (for T1 measurements) the values of A agreed with the values derived from 31P NMR measurements in crystals of Mn3(PO4)2 and Co3(PO4)2. From the similarity of A in crystals and complexes, we conclude that Mn2+ and Co2+ bind to the phosphates of AMP and RNA.
Nuclear Magnetic Resonance Study of Metal-Ion Binding to Adenosine Triphosphate. I. 31P Studies
Authors: Sternlicht H. , Shulman R. G. , Anderson E. W.
Published: January 2005

Measurements of the 31P NMR of the α, β, and γ phosphates of adenosine triphosphate (ATP) have been made for Mn2+—, Ni2+—, Co2+—, and Cu2+—ATP complexes. In order to explain the metal-ion—phosphate interaction, measurements were made at different values of f≡[M2+]/[ATP] between 0° and 95°C. The metal ions broadened the 31P NMR, described by a decrease in the observed value of T2; reduced T1, the spin—lattice relaxation time; and in the case of CoATP at high temperatures, shifted the resonance to lower fields by an amount ΔωM because of the transferred isotropic hyperfine coupling A. For Mn2+ and Ni2+ at all temperatures and CoATP at lower temperatures, T2 was determined by the chemical exchange time τM of the metal—phosphate bonds, and all three phosphates had the same widths. For CoATP at higher temperatures, the resonances were exchange narrowed and 1/T2≈fτMΔωM2. In agreement with the shift measurements 1/T2|γ>1/T2|β>1/T2|α. The values of A from the shifts were (in megacycles per second): Aγ=5.4, Aβ=4.5, and Aα=3.6 which were slightly larger than the values in Co3(PO4)2 crystals of 3.3. The large values of A in ATP show that the Co2+ is bound all the time to the phosphates. The T1 values for MnATP complexes are determined by dipolar interactions of the form 1/T1 ∝ (μ/r3)2τc. At room temperatures T1|γ=T1|β=34T1|α, which implies a very small difference in the distance of the metal ion from all three 31P nuclei. At higher temperature all three were equal. Assuming the phosphorous—metal distance of 3.3 Å, τc is determined to be ∼1×10−9 sec, which is about four times larger than the same correlation time for the water protons. From the high-temperature MnATP linewidths, which were all equal, we conclude that the hyperfine coupling with all three 31P nuclei is >0.6 times the value of A observed by Mays in LiMnPO4 crystals, once again showing that the binding to all three phosphates is approximately complete and approximately the same.
Influence of Hydrostatic Pressure upon Hydroxy and Methoxy Isomers of Substituted Anthracene and Naphthacene
Authors: McKelvey J. M. , King A. D.
Published: January 2005

The effects of hydrostatic pressure upon the long-wavelength absorption bands of 1- and 2-anthrols, and a newly synthesized, related compound, 2-methoxynaphtahcene, have been studied. The spectral shifts resulting from the application of hydrostatic pressure upon solutions of these compounds have been used as a means for distinguishing between overlapping transition. The observations by Baba and Suzuki concerning the anthrol spectra have been confirmed; and a correlation of the 2-methoxynaphthacene spectra with those of related hydroxy-substituted aromatic compounds is used to suggest a different band assignment from that predicted on the basis of resonance theory.
Magnetic Resonance Studies of Hyperfine Interactions in the Anion Radicals of Stilbene and Related Molecules
Authors: Johnson Charles S. , Chang Raymond
Published: January 2005

Electron spin resonance spectra are reported for the anions of tolan, stilbene, 1,2-bis(4-pyridyl)-ethylene, and azobenzene. In each experiment only one radical species was observed. The spectra were analyzed with the aid of third-derivative presentations and a nuclear magnetic resonance line-broadening experiment. All of the anions except tolan exhibit hindered rotation which allows the asymmetries of the spin-density distributions in the rings to be observed. Molecular orbital calculations with the McLachlan correction are in satisfactory agreement with the experimental hyperfine splitting constants. Methods for introducing asymmetry into the molecular orbital calculations are critically discussed and it is concluded that the so-called β effect is probably the most desirable of the crude corrections. It is argued on the basis of Hückel molecular orbital theory that moderately rapid isomerization is reasonable for the stilbene anion.
Optical Properties of Molecular Aggregates. II. Classical Theory of the Refraction, Absorption, and Optical Activity of Solutions and Crystals
Authors: DeVoe Howard
Published: January 2005

Classical theory is used to derive the optical parameters (refraction, extinction coefficient, reflectivity, rotation, and ellipticity) of a macroscopic sample containing aggregated monomer chemical units. The samples considered are dilute solutions of molecular aggregates or polymer molecules, and molecular crysstals. In this theory, each electronic transition of a monomer is represented by an electronic and a magnetic oscillator with complex polarizabilities which are evaluated empirically from the absorption and optical activity of unaggregated monomers. The complex refractive index for a refracted wave in the sample is obtained from Maxwell's equations and the electric and magnetic polarizations, taking into account Coulomb interactions between the oscillators. The optical parameters at any frequency are evaluated from the refractive indices for linearly or circularly polarized light. The results agree, in the same order of approximation, with those derived by several quantum theories. Sum rules are derived for the conservation of the monomer oscillator strengths and rotational strengths in the aggregates.
Phase-Space Theory of Chemical Kinetics. II. Ion—Molecule Reactions
Authors: Light J. C. , Lin J.
Published: January 2005

The revised phase-space (or statistical) theory of chemical kinetics has been used to compute cross sections for simple ion—molecule reactions. Reaction rates and isotope effects were investigated for bimolecular exchange reactions of the types X++HD→X++HDXH++D,(X is He,Ne,Ar,Kr)XD++HX+HD+→X+HD+XD++HXH++D.Dissociative charge-transfer reactions of rare-gas ions with CO were also investigated. Reasonable agreement with experiment, with no adjustable parameters used in the calculations, indicates that the phase-space theory has considerable predictive value in ab initio calculations of reactive cross sections for low-energy ion—molecule reactions.
Kinetic Studies of Hydroxyl Radicals in Shock Waves. V. Recombination via the H+O2+M→HO2+M Reaction in Lean Hydrogen—Oxygen Mixtures
Authors: Getzinger R. W. , Schott G. L.
Published: January 2005

Recombination in highly diluted, lean hydrogen—oxygen—argon mixtures with H2/O2 ratios of 0.50 and 0.33 has been investigated with a shock tube over the temperature range 1150°—1850°K for reaction pressures of 0.85–5.41 atm. An OH ultraviolet line absorption technique was used to follow the progress of the reaction after substantial equilibration of the rapid bimolecular reactions which form OH initially. It was determined that under these conditions the recombination process is third order and its rate, Rrec, obeys the empirical relationship Rrec=keff[H][O2][Ar].keff was found to decrease slightly with increasing temperature and to depend to a small extent upon the composition of the reacting mixture. The experimental results indicate that the reactionH+O2+M→ lim kHO2+Mdominates the recombination process. Further analysis of the data made it possible to obtain from keff a value of k(M = Ar) = 1.42×1015 cc2/mole2 sec at 1500°K and an estimate of k(M = H2O)/k(M = Ar) of about 30. This value of k(M = Ar) has been combined with other experimental determinations to obtain the expression k(M=Ar)=8.6×1014exp(1280±90/RT) cc2/mole2sec which describes the data to within 20% over the entire temperature range from 225° to 1850°K.
Electrical Properties of Ice. I. Dielectric Relaxation in Pure Ice
Authors: Dougherty Thomas J.
Published: January 2005

The work of Onsager and Dupuis and of Jaccard on the motion of Bjerrum faults in an applied field is extended to include effects due to interactions between Bjerrum faults and to relaxation of the Bjerrum fault atmosphere.
Integrated Intensity Measurements on the Fundamental and First Overtone Band Systems of CO Between 2500° and 5000°K
Authors: Breeze J. C. , Ferriso C. C.
Published: January 2005

Measurements have been made of the total absolute integrated intensities of the 4.7-μ fundamental and 2.4-μ first overtone band systems of CO at various temperatures within the range 2500° to 5000°K. The CO gas sample was studied in emission using a reflected shock wave to raise the sample to the high temperatures. Effects of vibrational relaxation, dissociation, and shock structure have been considered in the data interpretation.

Within the temperature range used in the present experiments, the integrated intensity of the CO fundamental band system remains constant. However, the integrated intensity of the CO first overtone band system shows a small increase with increasing temperature. The temperature dependencies of the two band systems are in agreement with the theoretical temperature dependencies. The present experimental results for CO extrapolated to STP are 289±29 and 2.3±0.3 cm−2·atm−1 for the total integrated band intensities of the fundamental and first overtone band systems, respectively.
Exchange Reactions with Activation Energy. I. Simple Barrier Potential for (H, H2)
Authors: Karplus M. , Porter R. N. , Sharma R. D.
Published: January 2005

A quasiclassical procedure for the examination of the collision dynamics of atom—diatomic-molecule reactions with activation energy is introduced. By means of Monte Carlo averages over a large number of appropriately chosen three-dimensional classical trajectories, the total reaction cross section (Sr) and other reaction attributes can be determined as a function of the initial relative velocity (Vr) and the initial molecular rotation-vibration state (J, ν).

The method is applied to the exchange reaction resulting from a hydrogen atom and a hydrogen molecule moving on a simple barrier potential of the London—Eyring—Polanyi—Sato type. It is found that Sr is a monotonically increasing function of relative velocity that rises smoothly from a threshold at ∼0.9×106 cm/sec to its asymptotic value of ∼4.5a02 at ∼1.8×106 cm/sec. The zero-point vibrational energy of the molecule contributes to the energy required for reaction, but the rotational energy does not. The reaction probability, which depends on VR, ν, and J, is found to be a smoothly decreasing function of the impact parameter (b) with a maximum of ∼0.6 for b=0 at high velocities. By integration of Sr over the distributions of VR, ν, and J corresponding to temperatures between 300° and 1000°K, a rate constant that can be fitted to an expression of the form K(T)=ATα exp[—Ea°/RT] is obtained, where A, Ea°, and α(α=1.1762) are constants. This temperature dependence is analyzed and contrasted with the results obtained from an absolute rate theory treatment based on the same surface.

A detailed examination of the collision trajectories shows no evidence for a long-lived ``collision complex''; instead the results are best represented by a direct interaction model with an interaction time on the order of that required for the atom to pass unimpeded by the molecule. For reactive collisions, the transition configuration is nonlinear with average angles of 170° for VR=0.93×106 cm/sec and 150° for VR=1.30×106 cm/sec; for nonreactive collisions, the average angle is between 95° and 125°, but has no simple relation to VR.
Preliminary Results of a Self-Consistent-Field Study of the Benzene Molecule
Authors: Schulman J. M. , Moskowitz J. W.
Published: January 2005

Self-consistent-field calculations, using small sets of Gaussian expansion functions, have been performed for the benzene molecule. All 42 electrons were considered explicitly. Some interspersion of sigma and pi levels has been found. Computed ionization potentials and electronic transition energies are given.
The Kinetics of Coordinate Bond Formation
Authors: Garvin David , Kistiakowsky G. B.
Published: January 2005

A novel method has been developed for determining the rates of very fast gas-phase bimolecular reactions, which is based on interpretation of the temperature gradients in a flow system similar to that used for the study of the reactions of sodium vapor and alkyl halides. The kinetics of the reactions between boron tri-fluoride and tri-, di-, and monomethylamine to form the corresponding coordinately bonded compounds have been studied. These reactions appear to have negligibly small activation energies, and their rates show a pressure dependence consistent with a mechanism: y+z⇌yz*yz*+m→yz+m*in which the long-lived intermediate yz* must be stabilized by loss of energy in a collision. The random scatter of individual rate constants is about 20 percent.
Diffusion through an Interface—Ternary Systems
Authors: Tung L. H. , Drickamer H. G.
Published: January 2005

Diffusion measurements have been made at 22°C and at 40°C in the system phenol-H2SO4-water, using S35 tagged H2SO4 as a radioactive tracer. Measurements made through the interface indicate that a significant resistance resides in the interface at both temperatures, and that the solution chemistry of the system must be quite complex. The relation of the results to practical mass transfer problems is briefly discussed.
The Heat of Formation of Nitric Oxide and Phosphorus Trioxide
Authors: Koerner William E. , Daniels Farrington
Published: January 2005

The heat of formation of nitric oxide has been redetermined by burning samples of red phosphorus in nitric oxide and in an equimolecular mixture of nitrogen and oxygen. A varying fraction of the phosphorus consumed by reaction with nitric oxide was converted to phosphorus trioxide; the remainder being converted to the pentoxide. A value of 21.8 kcal per mole was obtained for the heat of formation of nitric oxide at 25°C. A value of −270 kcal per mole was chosen as the best value for the heat of formation of phosphorus trioxide at 25°C.
The Microwave Spectra of the Deuterated Methyl Halides
Authors: Simmons James W. , Goldstein J. H.
Published: January 2005

The hyperfine structure lines of the pure rotational absorption transitions J=0→1 for CD3Cl and J=1→2 for CD3Br and CD3I, all in the ground vibrational state, have been measured in frequency and yield the following values of ν0 in Mc/sec and IB in g cm2×10−40, respectively: for CD3Cl35, 21683.75 and 77.3764; for CD3Cl37, 21316.86 and 78.7081; for CD3Br79, 30858.29 and 108.743; for CD3Br81, 30724.93 and 109.215; for CD3I, 24161.13 and 138.885. The quadrupole coupling coefficient, eqQ, has been determined for each of these molecules and its variation from eqQ for the corresponding normal methyl halide compound is considered.
The Diamagnetism of Ammonium Ion
Authors: Prasad Mata , Kanekar C. R. , Khanolkar D. D. , Datar M. G.
Published: January 2005

A linear relation between the molar susceptibilities of inorganic and organic salts of Li, NH4, and K containing a common anion and the number of electrons in the cations has been established. This relation has been used to deduce susceptibilities of ammonium ion and inorganic and organic anions in combination with it.
Force Constants and Calculated Thermodynamic Properties of Nitrosyl Fluoride
Authors: Stephenson C. V. , Jones E. A.
Published: January 2005

The force constants for NOF were calculated using the Wilson FG Matrix method. Unique values could not be calculated, since the number of force constants exceeded the number of fundamental vibrations. However, upper and lower limits have been set for the force constants. The thermodynamic functions for NOF were calculated for temperatures ranging from 273.16°K to 1500°K, using the rigid rotator, harmonic oscillator approximation.
On the Infrared Spectrum of Hydrazine
Authors: Giguère Paul A. , Liu I. D.
Published: January 2005

The absorption spectrum of hydrazine was reexamined in the region 1.5–25μ with a prism instrument. In the vapor some twenty bands were found of which a few are appreciably different from previous data. The low frequency fundamentals showed enough structural details to make possible a rough calculation of the rotational constants of the molecule. Because of extensive overlapping the identification and assignment of certain bands remain doubtful. The absorption spectrum of the liquid and that of the solid at −70° were also measured over a limited range.
Diffusion in Indium Near the Melting Point
Authors: Eckert Roger E. , Drickamer H. G.
Published: January 2005

Diffusion coefficients for the systems Tl204–In and In114–In have been measured in the solid state and in the neighborhood of the melting point. The measurements were made in both polycrystalline masses and in single crystals. For the polycrystalline samples a rapid, but not discontinuous, rise in the diffusion co-efficient occurred about 0.5°C below the melting point. For the Tl204–In system in a single crystal the rise in D occurs just below the melting point. This indicates grain boundary melting in the polycrystalline sample. For the In114–In diffusion in a single crystal the rapid rise still occurred well below the melting point, indicating that increasing lattice disorder also contributes to the increase in D.
The NH Stretching Vibration and NH–N Hydrogen Bonding in Several Aromatic Compounds
Authors: Fuson Nelson , Josien Marie-Louise , Powell Robert L. , Utterback Emery
Published: January 2005

The three-micron infrared absorption bands assigned to the NH stretching vibration have been studied in pyrrole, indole, carbazole, diphenylamine, and aniline. Spectra have been obtained in solution in carbon tetrachloride, carbon disulfide, chloroform, and benzene over a wide range of concentrations. In pyrrole and indole with increasing concentration the sharp NH band fades out and a broader band to lower frequencies appears. While the results are not as clearcut for diphenylamine and aniline, for these four compounds hydrogen bonding satisfactorily explains the observed data. This conclusion, for pyrrole and indole, sets aside the infrared spectroscopic basis for Pauling's hypothesis of two species of molecules. Carbazole was not soluble enough to make association studies possible. The relation of both the solvent and the solute molecular structure to the position of the associated and unassociated frequencies is discussed.
Adsorption Studies on Clay Minerals. I. Chromatography on Clays
Authors: Faucher Joseph A. , Southworth Raymond W. , Thomas Henry C.
Published: January 2005

With the aid of chromatographic columns containing a clay mineral dispersed on asbestos, ion-exchange processes on this mineral have been studied. The results of isotopic exchanges show that the columns do not run under equilibrium conditions. These isotopic exchanges do make possible a correction procedure which serves to produce isotherms for cases of true ion-exchange. The details of the correction procedure are given together with some results for a cesium-sodium exchange on a montmorillonite from Chambers, Arizona.
Kinetics of OH Radicals from Flame Emission Spectra. IV. A Study of the Hydrogen-Oxygen Flame
Authors: Broida H. P. , Shuler K. E.
Published: January 2005

The inner and outer cones of hydrogen-oxygen flames burning lean (1:1), stoichiometric (2:1), and rich (4:1, 6:1) at atmospheric pressure have been studied spectroscopically with the object of gaining some information as to the elementary processes occurring in this flame. The rotational, vibrational, and electronic distribution of OH(2Σ+) has been determined for both the inner and outer cone of each fuel mixture. A thermal equilibrium distribution of the internal degrees of freedom was found for OH(2Σ+) in the outer cones for all fuel ratios; in the inner cones there was a vibrational nonequilibrium distribution indicated by an excess population of the levels v′=2 and 3. It is suggested that this nonequilibrium may be due to a radiationless transition reaction involving H or O atoms in excess of their thermal concentrations. This assumes, in agreement with the suggestion of Gaydon and Wolfhard, that the 2Σ+ state of OH is weakly predissociated between the levels v′=2 and 3 by a 2Σ− state. The possible significance of this excess atomic concentration for the active particle diffusion theory of flame propagation is indicated briefly. It is concluded that the radiation of OH(2Σ+) in the oxy-hydrogen flame is predominantly thermal.
Precise Measurements in the Infrared Spectrum of Carbon Monoxide
Authors: Plyler Earle K. , Benedict W. S. , Silverman Shirleigh
Published: January 2005

New measurements have been made in the CO infrared spectrum in both emission and absorption, using a 15,000-line/inch grating spectrograph and a 7200-line/inch vacuum grating spectrograph. High precision in wavelength determinations was obtained by superimposing on the spectra emission lines in higher order of Hg, Kr, and A discharges. The measurements are believed accurate to ±0.02 cm−1. The observed lines in absorption are those of the 2–0 and 3–0 bands of C12O16, between R 30—P 29 and R 9—P 16, respectively; 27 lines of C13O16 and 10 lines of C12O18 have also been measured. In emission from oxy-acetylene and CO–O2 flames, over 300 lines in the 2–0, 3–1, 4–2, and 5–3 bands have been identified between 4360 and 4000 cm−1. The emission bands form heads in the R branch near J=50, and the 2–0 band shows resolved lines out to J=46 in both P and R branches.

The new measurements are in good agreement with earlier results at low quantum numbers, but show discrepancies at high numbers which result in slightly different values for the molecular constants, especially in ye and De. Our constants are in cm−12169.81 lim ωe       13.284 lim xeωe       0.010 lim yeωe       1.93130 lim Be   0.017543 lim α       4.5×10−6 lim γ      5.95×10−6 lim De      0 lim β  

The observed isotope shifts of the 2–0 band origin for C12–C13 and O16–O18 are, respectively, 93.27±0.02 cm−1 and 101.03±0.05 cm−1, in good agreement with the calculated values.

The emission spectra permit the determination of rotational ``temperatures'' with an accuracy of ±5 percent and vibrational ``temperatures'' with an accuracy of ±10 percent. Thermal equilibrium between the two modes is observed in the outer cone of the flames, but in the region just above the reaction zone, the rotational temperatures are several hundred degrees higher than the vibrational values or the calculated equilibrium values.
Transition Probabilities. II. Calculation of Semi-Theoretical f-Numbers for Hydrogen Using the Dipole Velocity Operator
Authors: Shull Harrison
Published: January 2005

The computations of Mulliken and Rieke using the LCAO MO and the AO methods for transition probabilities of the Lyman (1Σg+—1Σu+) and Werner (1Σg+—1πu) transitions in hydrogen have been repeated using the alternative velocity form of the transition moment operator. It is found that, for an effective Z value of 1.2 for the 1s AO (the variation value) and a suitable Rydberg form for the excited state, the transition probabilities calculated from these two operators agree well. In addition there is quite good agreement between the AO and MO methods in each instance and between the calculated and experimental value for the sum of the strengths of the Lyman and Werner transitions.
Kinetics of Decomposition of Nitric Oxide at Elevated Temperatures. I. Rate Measurements in a Quartz Vessel
Authors: Wise Henry , Frech Maurice F.
Published: January 2005

The rate of thermal decomposition of nitric oxide has been measured in a quartz vessel from 872 to 1275°K. The reaction follows a second-order rate law over the range of temperatures studied. Variations in the surface-to-volume ratio of the reaction vessel indicate the predominance of a heterogeneous mechanism at temperatures below 1000°K, whereas at higher temperatures a homogeneous mechanism prevails. The experimental data are interpreted on the basis of the relative contribution of the heterogeneous and homogeneous mechanisms to the over-all kinetics. Such an analysis explains the variation in effective activation energy with temperature from a value of 21.4 kcal below 1000°K to 82 kcal above 1600°K. An intermediate temperature region exists in which both mechanisms contribute an important part to the over-all rate.
The Interlayer Binding in Graphite
Authors: Brennan Robert O.
Published: January 2005

The repulsive energy between layers of the graphite crystal has been calculated as an interaction of LCAO molecular orbitals in the layers. The van der Waals attractive term was found by setting the energy minimum to fall at 3.37A. When values of the effective nuclear charge and effective quantum number proposed by Kohlrausch were used, the interlayer binding energy was found to be 3.99 kcal/mole. The compressibility, calculated under plausible assumptions, is in satisfactory agreement with the experimental value.
Macro-Ions. I. Light Scattering Theory and Experiments with Bovine Serum Albumin
Authors: Doty Paul , Steiner Robert F.
Published: January 2005

The theory of light scattering is extended to include solutions of macro-ion salts such as charged proteins and polymeric electrolytes. Equations for the angular intensity distribution are obtained for three types of interaction potential: (1) that of rigid, non-interacting spheres, (2) an electrostatic potential consistent with the Verwey-Overbeek theory, and (3) a simple Gaussian-type repulsion. Because the repulsive forces between the macro-ions are generally strong and long range, the concentration and angular distribution of the scattering may be very pronounced. Two unique and important extremes exist. If the concentration of the macro-ion salt is altered without introducing additional electrolytes, the effective diameter of the macro-ion is inversely proportional to the cube root of the concentration. In this situation the essential features of the scattering are quite novel. First, the reciprocal reduced intensity rises steeply from the intercept at zero concentration, bends over and becomes nearly horizontal at moderate concentrations, and second, the dissymmetry falls sharply from the limiting value at zero concentration, passes through a minimum and rises slowly at higher concentrations. With small particles the dissymmetry is always less than unity. In experiments with bovine serum albumin carrying charges up to 50 protons, all of these features have been found and can be accounted for at least semiquantitatively. The second unique case is that occurring when the concentration is altered by isoionic dilution which keeps the effective diameter of the macro-ion constant. Since it is shown that in the scattering problems the difference between the hard sphere and electrostatic potential is relatively minor, the virial coefficients of Boltzmann can be used to describe the concentration dependence of the absolute intensity of scattering. This procedure permits, in contrast to the previous case, a precise evaluation of the effective ionic diameter. The values so obtained are compared with estimates from the Debye-Huckel theory. As a consequence of these investigations, it appears that both the thermodynamic behavior and diffraction behavior of macro-ion solutions are consistent with a relatively simple electrostatic picture.
Rotation-Vibration Spectra of Diatomic and Simple Polyatomic Molecules with Long Absorbing Paths VII. The Spectrum of Dideuteroacetylene (C2D2) in the Photographic Infrared
Authors: Saksena B. D.
Published: January 2005

Twelve absorption bands of C2D2 have been observed in the photographic infrared. Eleven of these bands show simple P and R branches with intensity alternation, i.e., they are Σu+—Σg+ bands while one band, without intensity alternation, is a difference band of type Π—Π. From the positions of the bands some of the vibrational constants ωi0 and xik are determined. In addition, from the rotational fine structure, the rotational constants B[v] and D[v] are determined. For B[0] the value 0.84787 cm−1 is obtained. The αi values are α1=+0.00578, α2=+0.00302, α3=+0.00455, α4=−0.00120, α5=−0.0026 cm−1. From the αi and B[0] one obtains Be=0.85075 cm−1. Combining Be(C2D2) with Be(C2H2) yields, for the internuclear distances in the acetylene molecule, re(C≡C)=1.2010×10−8 and re(C–H)=1.0637×10−8 cm in very satisfactory agreement with the values previously obtained from Be(C2HD) and Be(C2H2). Evidence for l-type doubling in C2D2 is given and approximate values for the l-type doubling constants q4 and q5 are obtained.
Inter- and Intramolecular Energy Transfer Processes. 2. Hydrocarbon-Hydrocarbon Systems
Authors: Moodie Margaret M. , Reid C.
Published: January 2005

The transfer of energy from one species of hydrocarbon to another has been observed. The conditions under which such transfer occurs indicate that one aromatic hydrocarbon may be adsorbed onto crystals of the other forming a surface complex with a binding energy of a few hundred calories. Transfer of energy occurs readily between the components of this complex but not between molecules of different hydrocarbons when both are in solution. However, evidence for resonance transfer of energy between pairs of molecules of the same substance when both are in solid solution has been found.
Molecular Structure of Bromoform
Authors: Williams Quitman , Cox John T. , Gordy Walter
Published: January 2005

The structure of bromoform has been evaluated entirely from microwave spectroscopy. The B0 values in Mc/s of the isotopic species studied are: 1247.61±0.025 for CHBr379; 1217.30±0.025 for CHBr381; 1239.45±0.025 for CDBr379; 1209.51±0.025 for CDBr381. These constants yield the structure as follows: dCH=1.07A±0.01A, dCBr=1.930A±0.003A, angle BrCBr=110°48′±16′.
The Free Volume Theory of Multicomponent Fluid Mixtures
Authors: Salsburg Zevi W. , Kirkwood John G.
Published: January 2005

The free volume theory of the liquid state is extended to multicomponent mixtures by using the method of moments in the treatment of the order-disorder problem. Retention of only the first moment yields an approximation to the partition function which has recently been studied by Prigogine and Garikian and by Prigogine and Mathot. An approximation equivalent to retaining the third moment is given, and the calculation of the thermodynamic functions from the first moment approximation is discussed.
Thermodynamic Properties of the Diatomic Interhalogens from Spectroscopic Data
Authors: Cole Leland G. , Elverum Gerard W.
Published: January 2005

The thermodynamic functions Cp0, S0, —(F0—E00)/T, and (H0—E00)/T of the six diatomic interhalogens, chlorine monofluoride, bromine monofluoride, iodine monofluoride, bromine monochloride, iodine monochloride, and iodine monobromide, have been evaluated as a function of temperature from 298.16°K to 2000°K by the application of statistical methods. These results have been combined with newly evaluated properties of the fluorine, chlorine, bromine, and iodine atoms and molecules to yield the heats and free energies of dissociation and dissociation constants for the equilibria between the interhalogens and their molecular and atomic dissociation products. The calculations are based on available experimental spectroscopic constants with the exception of the anharmonicity term and internuclear distance for bromine chloride and of the internuclear distances in iodine fluoride and iodine bromide. These quantities are estimated empirically.
Reactions of Methane with Iodine Activated by Radiative Neutron Capture
Authors: Hornig J. F. , Levey G. , Willard J. E.
Published: January 2005

About 50 percent of the I128 atoms formed by the I127(n, γ)I128 reaction in gaseous mixtures of 0.2 mm of iodine and 400 mm of methane enter combination as methyl iodide, whereas much less than 1 percent of iodine atoms produced simultaneously by the photochemical dissociation of the iodine do so. By contrast, about 1 percent of the I128 formed by the I127(n, γ)I128 reaction in gaseous mixtures of iodine and ethyl iodide enters organic combination.

The solubility of iodine in pure liquid methane is less than 10−10 m/1 but as much as 3×10−5 m/1 may be dissolved when air has been allowed to condense in the methane. In such solutions I128 from the I127(n, γ)I128 reaction is able to enter organic combination as methyl iodide, ethyl iodide, and higher boiling material.
The Induction Period in Chain Reactions
Authors: Benson Sidney W.
Published: January 2005

The conditions for the establishment of a stationary state in a system of consecutive reactions can be investigated quantitatively in a sufficient number of cases to permit precise criteria to be formulated generally for the length of the induction period (i.e., prestationary state period) in chain reactions. These are given as functions of the individual rate constants for the separate reactions, the extent of the reaction and the percent of stationary state concentrations achieved. Such relations provide a means for the evaluation of the self-consistency of experimental data with proposed mechanisms and also provide numerical limits on the values of individual rate constants.

Various chain reactions are examined in the light of these criteria. Of the hydrogen-halogen reactions, the H2–Cl2 reaction mechanism does not fulfill the stationary state requirements, and it is probable that many of the discordant results found in this reaction arise from this difficulty.
Intermolecular Potentials for the Systems CO2–CO2 and CO2–N2O
Authors: Amdur I. , Ross J. , Mason E. A.
Published: January 2005

Experimental values of self-diffusion and mutual diffusion coefficients, in the range −78° to 90°C, have been used to determine the intermolecular potentials for the systems CO2–CO2 and CO2–N2O. It has been assumed that a spherically symmetric potential of the form V (r)=4ε[(σ/r)12—(σ/r)6] may be used and that the dynamics of the diffusion process are adequately described by the classical Chapman-Enskog transport relations, which consider only elastic, binary collisions.

The potential parameters derived from diffusion measurements have been compared with those obtained from measurements of viscosity, compressibility, the critical temperature, and the critical volume. It was not possible, for either system, to obtain a single set of parameters which could satisfactorily reproduce all the gaseous properties. It has been concluded that, for the present systems, the failure is due to one or both of the following: (1) inadequacy of the assumed potential form, (2) importance of inelastic collisions.
Tables of the Lennard-Jones and Devonshire Equation of State at High Temperatures and Densities
Authors: Fickett W. , Wood Wm. W.
Published: January 2005

The Lennard-Jones and Devonshire equation of state is computed for the following ranges of the reduced variables: temperature, kT/ε*, 20 to 150 in steps of 10; volume, v/v*, 0.3 to 0.7 in steps of 0.05 and 0.7 to 1.3 in steps of 0.1.
Infrared and Raman Spectroscopy Studies of Light and Heavy Trifluoroacetic Acids
Authors: Fuson Nelson , Josien Marie-Louise , Jones Ernest A. , Lawson James R.
Published: January 2005

An infrared and Raman spectroscopic study of light and heavy trifluoroacetic acids shows that their vapors at room temperature are composed of a mixture of monomeric and associated molecules. The principal bands corresponding to vibrations of the COOH and COOD groups have been identified for both the monomeric and the associated molecules by means of a comparative study of the two acids (a) in the vapor state at different pressures, (b) in CCl4 solutions at various concentrations, and (c) in the liquid state. The monomeric carbonyl frequencies, influenced by the presence of the perfluoromethyl group, are the highest yet reported in the literature; this is true not only for CF3COOH (1826 cm−1, vapor), CF3COOD (1823 cm−1, vapor), but also for the ethyl ester, CF3COOC2H5 (1802 cm−1, vapor), the sodium salt, CF3COONa (1687 cm−1, solid), and the anhydride (CF3COO)2O (1884 cm−1 and 1818 cm−1, vapor). On the basis of a comparative study of the spectra of all these compounds, as well as of other perfluoromethyl compound spectra reported in the literature, the C–F stretching vibrations for the two acids have been assigned to the strong infrared absorptions at 1244 cm−1 and 1185 cm−1. The corresponding Raman bands are very weak.
Two-Center Heteronuclear Hybrid Coulomb-Exchange Integrals
Authors: Brennan R. O. , Mulligan J. F.
Published: January 2005

The method introduced by Sklar and Lyddane, and used by Parr and Crawford, to evaluate two-center hybrid Coulomb-exchange integrals involving atoms with equal effective nuclear charges has been extended to include the case of unequal effective nuclear charges. Formulas for all thirty nonvanishing integrals of this type involving 2s and 2p Slater atomic orbitals (assuming that the 2s and 2p orbitals on the same atom have the same screening) are given in a form convenient for numerical calculations. These formulas are valid for both the homonuclear and the heteronuclear cases. The method here given has the advantage that all the integrals are expressed in terms of natural logarithms, exponentials, and exponential integrals, adequate tables of which are readily available. Exact numerical values obtained by this method for thirty hybrids involving carbon and oxygen atomic orbitals in CO2 are given. These exact values have been used as a check on the validity of an approximation previously employed for these integrals.
The Thermal Dimerization of Butadiene, and the Equilibrium between Butadiene and Vinylcyclohexene
Authors: Duncan N. E. , Janz G. J.
Published: January 2005

The kinetics of the dimerization of butadiene and of the dissociation of vinylcyclohexene have been considered in the light of thermodynamic equilibrium calculations. The lack of accord between the results is resolved if the dissociation of vinylcyclohexene is given by the rate expression kd=5.02×1015exp(−61,800/RT) sec−1.
Low Temperature Second Virial Coefficients for a 6–9 Potential
Authors: Roe Glenn M. , Epstein Leo F. , Powers Marion D.
Published: January 2005

Alternate expressions for the second virial coefficient of a gas having a Lennard-Jones 6–9 potential are derived to cover the temperature range where the known power series expansion in θ=ε/kT is inconvenient for numerical computations. For θ≥2 the second virial coefficient can be expressed as a combination of Bessel functions of imaginary argument plus a small correction term. This formulation and an asymptotic expression derived from it are used to tabulate numerical values of the second virial coefficient in the range 2≤θ≤100.
The Quenching of Mercury Resonance Radiation. II. The Production of Metastable (3P0) Atoms
Authors: Darwent B. deB. , Hurtubise F. G.
Published: January 2005

The production of metastable (3P0) mercury atoms in the quenching of mercury resonance radiation has been investigated with N2, H2, C2H4, C2H6, O2, and CO2. Metastable atoms, by virtue of their ability to induce the emission of electrons from a nickel surface, were detected with the first four gases; none was detected with O2 and CO2.
Microwave Spectra and Structures of XYH3 Molecules
Authors: Mays John M. , Dailey Benjamin P.
Published: January 2005

Work on the microwave spectra of CH3Cl, SiH3Cl, GeH3Cl, CH3Br, SiH3Br, and GeH3Br, performed at this laboratory and others, is summarized, and preliminary reports of work at this laboratory are expanded. Structural parameters, dipole moments, and quadrupole coupling constants obtained from analysis of these spectra are tabulated and discussed, and a unified picture of the bonding in these series of molecules, based on the derived quantities, is presented.
The Molecular Structure of Cyclopropene, C3C4
Authors: Dunitz J. D. , Feldman H. G. , Schomaker Verner
Published: January 2005

Cyclopropene, C3H4, has been investigated by the electron diffraction method. The cyclic structure is confirmed and the following interatomic distances and angles are found: C–C, 1.525±0.02 A; C=C, 1.286±0.04 A; 〈C–H〉, 1.087±0.04 A; ∠H–C–H, 118° (assumed); ∠C=C–H, 152±12°.
The Asymmetric Rotor. X. The Hydrogen Sulfide Spectrum in the 5150 cm−1 Region
Authors: Allen Harry C. , Cross Paul C. , Wilson M. K.
Published: January 2005

The absorption spectrum of hydrogen sulfide in the region from 5000 to 5250 cm−1 has been measured and the rotational fine structure analyzed. The structure can be accounted for as arising from two vibrational transitions yielding a type A band centered at 5147 cm−1 and a type B band centered at 5145 cm−1. The excited state constants giving the best fit are type A band, A*=10.04, B*=8.68, C*=4.61 cm−1; type B band, A*=10.08, B*=8.68, C*=4.59 cm−1.

The frequencies and rotational band types indicate that these bands are the (nσ, nπ, nδ)=(110) (type A) and the lower component of the resonating pair (020) (200) (type B).
Diffusion of Acetone into Polyvinyl Acetate above and below the Second-Order Transition
Authors: Kokes R. J. , Long F. A. , Hoard J. L.
Published: January 2005

The sorption kinetics for the system polyvinyl acetate-acetone have been investigated both above and below 30°C, the second-order transition temperature for the pure polymer. At 30, 40, and 50°C, the diffusion obeys Fick's law with a concentration-dependent diffusion coefficient. With increasing acetone concentration the value of the diffusion coefficient increases strongly, and the energy of activation for diffusion decreases. At each temperature below 30°C, diffusion is Fickian only for sorption and desorption experiments where the solvent concentration is above a certain critical value. It was found, by comparison with the results of volume-temperature measurements on the system polyvinyl acetate-acetonyl acetone, that the temperature corresponding to a given critical concentration is the second-order transition temperature for this polymer-solvent mixture. Evidently, the changes which occur at the second-order transition have a pronounced influence on the diffusion process.
The Infrared Spectra of NF3 and PF3
Authors: Wilson M. Kent , Polo Santiago R.
Published: January 2005

The infrared spectra of NF3 and PF3 have been investigated with a prism instrument in the range 250 cm−1 to 5000 cm−1. The fundamental frequencies are for NF3, ν1(A1)=1032 cm−1, ν2(A1)=647 cm−1, ν3(E)=905 cm−1, and ν4(E)=493 cm−1; and for PF3, ν1(A1)=892 cm−1, ν2(A1)=487 cm−1, ν3(E)=860 cm−1, and ν4(E)=344 cm−1. Force constants as well as thermodynamic functions are calculated for both molecules.
Rotational Isomers of Chloroacetyl Chloride, Bromoacetyl Chloride, and Bromoacetyl Bromide
Authors: Nakagawa Ichiro , Ichishima Isao , Kuratani Kenji , Miyazawa Tatsuo , Shimanouchi Takehiko , Mizushima San-ichiro
Published: January 2005

The Raman spectra of chloroacetyl chloride, bromoacetyl chloride, and bromoacetyl bromide have been measured in the solid and liquid states. The infrared absorption spectra of these substances have also been measured in the liquid and the gaseous states. From the experimental results it has been concluded that there are two rotational isomers in the liquid and gaseous states and only one of them persists in the solid state. The temperature dependence of the intensity of the infrared absorption in the gaseous state has also been studied, and the energy difference between these two isomers has been found as 1.0±0.1 kcal/mol for bromoacetyl chloride and 1.9±0.3 kcal/mol for bromoacetyl bromide.

The calculation of the normal vibrations and of the product rule has been made for various configurations of rotational isomers, and it has been shown that the more stable form is the trans form (or nearly this one) with regard to the two halogen atoms. The less stable form is considered to have an azimuthal angle between the two carbon-halogen bonds of about 150°.
On the New Absorption Bands of the Oxygen Molecule in the Far Ultraviolet Region
Authors: Tanaka Yoshio
Published: January 2005

The absorption bands of the oxygen molecule in the extreme ultraviolet region were studied using a 3-meter grazing incidence vacuum spectrograph. Two new progressions of bands were found in the region between 1200A and 1290A (one of which is considered to be a member of the Rydberg series converging to the first ionization potential of the oxygen molecule). There were also observed a few short continua near the short wavelength end of the Schumann-Runge absorption continuum. The behavior of three strong and diffuse bands, at 1200∼1290A, were studied at pressures ranging from 0.01 to several mm of Hg. Assuming the diffuseness of these bands as being due to predissociation, the existence of oxygen atoms in 1S metastable states in the upper atmosphere is briefly discussed.
A Note on Rotational Line Strengths in Slightly Asymmetric Rotors
Authors: Lide David R.
Published: January 2005

Direction-cosine matrix elements for slightly asymmetric rotors are calculated by a second-order perturbation treatment around the limiting symmetric rotor. This permits evaluation of the line strengths which are involved in calculations of absorption intensities, Stark effects, and nuclear-quadrupole couplings in rotational spectra. Explicit formulas are derived for the first-order terms.