bluuebunny/crossref_metadata_2025_split huggingface dataset:
Intermolecular Coupling of Vibrations in Molecular Crystals. II. Intermolecular Forces in CH3Cl and CD3Cl
Authors: Dows David A. 
Published: January 2005

The effect of isotope substitution on band splittings caused by dipole coupling between molecules is examined. For methyl chloride and methyl bromide, the results support the contention that the theory of dipole coupling in its present form is not sufficient to explain the splittings in most bands.
The theory of atom-atom interactions presented in part I of this series is applied to various possible potentials coupling the motions of normal and deuterated methyl chloride molecules. A repulsive potential acting between hydrogen atoms of neighboring molecules accounts for the splittings of several bands. Certain types of coupling potentials seem ruled out by the results of these calculations, while others are left as possible factors in band shifts which occur when a gas is condensed.
Interpretation of the Absorption Spectra of K3Fe(CN)6
Authors: Naiman C. S. 
Published: January 2005

By interpreting the absorption spectra of K3Fe(CN)6 in solution, we are able to explain the results of the pressure dependence of the solid spectra, obtained by Parsons and Drickamer.
The intense absorptions at 24 000 and 32 900 cm—1, are identified as charge-transfer spectra from the ligand to the T2g level of the metal ion, while the one at 38 460 cm—1 is identified as the same type of transition, but into the Eg level. Fitting of the weaker spectra yields the values of 3500, 720, and 3285 cm—1 for the crystalline field parameters Dq, B, and C, respectively.
One of the results of Parsons and Drickamer shows evidence of a charge-transfer transition that is symmetry restricted, and made allowed by vibrational-electronic perturbations. A perturbation treatment is carried out that follows the method developed by Liehr and Ballhausen for the dn→dn crystal-field transitions, that are also symmetry forbidden.
Finally, two types of experiments that would test the proposed explanations are described.
Mean and Equilibrium Molecular Structures of Methane and Deuteromethane as Determined by Electron Diffraction
Authors: Bartell L. S. , Kuchitsu Kozo , deNeui R. J. 
Published: January 2005

The structural parameters of methane and methane-d4 were determined with the new rotating-sector electron diffraction apparatus of Iowa State University. The results demonstrated, for the first time by electron diffraction, the existence of isotope effects on structure. Mean internuclear distances were C–H=1.1068±0.001 A, C—D=1.1027±0.001 A, H···H=1.811±0.007 A and D···D=1.805±0.008 A. Mean amplitudes, reckoned from mean positions, were C–H=0.0751±0.002 A, C—D=0.0663±0.002 A, H···H=0.120±0.006 A, and D···D=0.105±0.006 A.
The isotope effects were just those expected for atoms of different mass vibrating in identical anharmonic force fields. Vibrational anharmonicity led to measurable phase shifts in the molecular diffraction patterns from which the asymmetry of the internuclear distribution functions could be determined. This allowed a direct experimental determination of the approximate equilibrium C–H and C—D bond lengths, giving 1.082 A. Somewhat more rigorous calculations of the correction from mean to equilibrium distances based on an anharmonic Urey-Bradley field led to equilibrium C–H and C—D bond lengths of 1.0847 A and 1.0863 A, respectively. Corresponding equilibrium bond lengths computed from the spectroscopic r0 values of 1.0940 A and 1.0923 A, respectively, were 1.0850 A and 1.0856 A. The comparison clearly illustrates the appreciable difference between electron diffraction and spectroscopic methods in the manner of averaging over molecular motions, but also confirms the essential equivalence of molecular information derived, if suitable corrections are applied to each.
Structural Effects in the Vapor Pressures of Isotopic Molecules. O18 and N15 Substitution in N2O
Authors: Bigeleisen Jacob , Ribnikar Slobodan V. 
Published: January 2005

The relative vapor pressure ratios of the isotopic N2O molecules have been determined by distillation in a column under total reflux. It is shown that the vapor pressures are in the sequence N14N14O16&gt;N14N15O16&gt;N15N14O16&gt;N14N14O18.The absolute vapor pressure ratios have been determined from the kinetic behavior of the column and the decrease in separation by production from the column.
Theoretical calculations of the relative vapor pressure ratios can be made from the atomic masses and the random structure of liquid N2O. The calculated relative isotope effects are in good agreement with experiment. The absolute value of ln PN14N14O16/PN14N15O16 is calculated from the specific heat of N2O to be 8.2×10—4 at 184°K, in good agreement with the experimental value 7.8±1.4×10−4. The difference in vapor pressures of the isotopic isomers N14N15O16 and N15N14O16 is attributed to hindered rotation of the molecule in the liquid.
Electrical Properties of Nonstoichiometric Uranium Dioxide
Authors: Aronson S. , Rulli J. E. , Schaner B. E. 
Published: January 2005

Electrical conductivity and thermoelectric power measurements have been made on nonstoichiometric UO2 at temperatures of 500–1150°C. The conductivity data in the single phase UO2+x region can be represented by the equation σ(ohm cm)−1=(3.8×106)/T(2x)(1−2x) exp[(−0.30±0.03 ev)/kT].An approximate equation for the thermoelectric power Q, is Q=(k/e) ln(1−2x/2x).
The electrical measurements confirm the ionic theory of nonstoichiometry in UO2, postulated on the basis of thermodynamic evidence. Nonstoichiometric UO2 is a relatively simple ionic solid in which activated electronic hole transfer occurs between U5+ and U4+ ions in the lattice.
Mutual Diffusion of the Gas Pairs H2–Ne, H2–Ar, and H2–Xe at Different Temperatures
Authors: Paul R. , Srivastava I. B. 
Published: January 2005

The mutual diffusion coefficients of H2 with Ne, Ar, and Xe have been determined by the two-bulb technique of Ney and Armistead in the temperature range —30° to 68°C. Diffusion was allowed to take place through a precision capillary tube connecting the two diffusion bulbs and samples of the gas were analyzed at different times with the help of a previously calibrated thermal-conductivity analyzer.
A least-square method was then followed to calculate the force constants on the Lennard-Jones (12:6) potential model from the experimental values of the diffusion coefficients. Also, using experimental values of the mutual-diffusion coefficient, thermal conductivity, and viscosity of pure components, the thermal conductivity of various mixtures were calculated and a good agreement with the experimental data was obtained.
Markoff Chain Model for Growth of Polymer Single Crystals
Authors: Price Fraser P. 
Published: January 2005

A theory is presented wherein the development of a polymer single crystal is envisioned as the successive coherent addition of layers of segments of polymer molecules, each layer acting as the substrate for the succeeding layer. The substrate is assumed smooth and the distribution of segment lengths in the next layer is assumed to be controlled by equilibrium considerations. The theory predicts that as the supercooling is increased the energy gained due to the bulk energy of crystallization tends to overwhelm the energy lost due to formation of new surfaces. This has the result of making the average segment length of the adding layer closer and closer to the substrate length. In some cases it even exceeds the substrate length. The net result is that the temperature dependence of ultimate crystal thickness is not as great as was implied by the (ΔT)—1 laws of previous theories.
The theory has been satisfactorily fitted to the experimentally observed dependence on temperature of single crystals of linear polyethylene grown from dilute xylene solution. The parameters used to fit theory to experiment are a lateral surface energy of 13.3 ergs/cm2, an end (fold surface) energy of 110 ergs/cm2, and a solution temperature of 113°C. The theory also indicates that the surface of the polyethylene crystals is remarkably smooth with an average roughness of only one to two angstroms. Predictions are also made concerning the profile of a single crystal in the region of its primary nucleus (central region). It is shown that hollows, sharp spikes, or flat topped mesas of considerable extent may be observed depending on the supercooling.
s-Tetrazine. I. High-Resolution Vapor-Phase Study of the Visible n→π Vibronic Absorption Band Systems
Authors: Spencer Glenn H. , Cross Paul C. , Wiberg Kenneth B. 
Published: January 2005

The low-resolution electronic spectrum of s-tetrazine vapor has been measured down to about 190 mμ, and the complex systems of vibronic bands that comprise the n→π* visible absorption spectrum have been studied under higher resolution. These latter spectra were photoelectrically recorded in the third order of a 21-ft grating spectrograph, using path lengths from 0.05 to 48 m and temperatures from —70° to 70°C. In the absorption region, 4500 to 6100 A, the spectrum consists of over 500 sharp, vibronic band peaks. Their collected Q-branch maxima have been measured to the nearest cm—1, but no discrete rovibronic structure was resolved.
The outstanding feature of the visible spectrum is a set of four intense progressions, each of which is propagated by the consecutive excitation of the same vibration (believed to be the totally symmetric mode 6a). In the ground state, the frequency of this vibration is 737 cm—1 for s-tetrazine-d0 and 720 cm—1 for s-tetrazine-d2; these frequencies drop to about 700 and 690 cm—1, respectively, in the excited n→π* state(s). From simple molecular orbital theory and the Herzberg-Sponer-Teller selection rules, a plausible, preliminary, singlet absorption model is developed and is qualitatively applied to the spectral data. Because there may be an ``almost accidental degeneracy'' of some of the n→π* states of the azines (excluding pyridine), the need for a more elaborate model that will properly treat the electronic-vibrational interaction problem is emphasized. Although a complete vibronic analysis has not yet been obtained, the presence of three electronic transitions forbidden on the basis of D2h excited state molecular symmetry, as well as the electronically allowed n→π* transition, is suspected.
Construction of Reliable Internuclear Potential Curves from Equilibrium Bond Lengths and Vibrational Frequencies
Authors: Steele D. , Lippincott E. R. 
Published: January 2005

A method is presented for the construction of reliable internuclear potential curves using a previously proposed function and observed values of equilibrium bond lengths and vibrational frequencies. The function has the form V=De{1−exp[−(nΔr2/2r)]}{1+af(r)}.
An explicit form is presented for the observed periodicity of the parameter a when referring to the ground states of diatomic molecules. This periodicity is shown to lead to relationships from which De, αe, and xeωe can be calculated solely from ωe and re. An empirical relationship between the values of the parameter a in the ground and the excited states is presented from which De, αe, and xeωe can be deduced for any nonionic excited state from ωe and re of that state. This latter relationship demonstrates that ωere2 is not constant for all states of any molecule but is dependent in a predictable manner on the other spectroscopic constants. These relationships enable potential curves to be constructed solely from a knowledge of ωe and re. Calculated curves for the X1Σg+ states of H2 and I2 and ground and excited states of N2 agree extremely well with experimental curves, deviating by no more than 2% of the dissociation energy. The agreement is very good for large values of r for H2 and I2, which indicates that a general form exists for the interaction of bonding atoms at large distances.
A High-Resolution Study of CO2 Absorption Spectra between 15 and 18 Microns
Authors: Madden Robert P. 
Published: January 2005

A study has been made of the absorption due to individual lines and Q branches of CO2 bands in the 15-to 18-μ spectral region. The strengths and widths of absorption lines on the low-frequency side of the v2 fundamental band and in the 02°0–0110 band of C12O216 have been measured. In the latter band the variation of line strength and width with J has been determined as well as the Coriolis interaction parameter. The strengths of five other bands of C12O216 have been determined from measurements on their Q branches, and the strengths of the v2 fundamental bands of the isotopes C13O216 and O18C12O16 have been estimated. The rotational structure of the v2 fundamental Q branch for C12O216 is partially resolved, and the band constants determined. The v2 fundamental band head of the O18C12O16 isotope is reported.
The spectra were taken in 1956 after construction of the large infrared spectrometer at the Laboratory of Astrophysics and Physical Meteorology, The Johns Hopkins University. This f/6 spectrometer utilizes 3-in. long curved slits and a 14- by 12-in. grating in a Fastie-Ebert mounting. It is demonstrated that this instrument has available an optical slit width of 0.06 cm-1 at 17 μ.
Microwave Spectrum, Structure, Quadrupole Interaction, Dipole Moment, and Bent C–Cl Bonds in 1,1-dichlorocyclopropane
Authors: Flygare W. H. , Narath A. , Gwinn William D. 
Published: January 2005

The microwave spectrum of C3H4Cl235,35, C3H4Cl235,37, C3D4Cl235,35 C3D4Cl235,37, C3H3DCl235,35, C3H3DCl235,37 (cis and trans), and C2C13H4Cl235,35 have been investigated. Using the derived rotational constants, a complete structure for the molecule is calculated. The structural parameters are dC–H=1.085 A, dC(2)–C(3)=1.534 A, dC(1)–C(2)=1.532 A, dC–Cl=1.734 A, ∠H–C–H=117°35′, ∠C(2)–C(3)–H2=153°37′±15′, ∠Cl–C–Cl=114°38′. κ for C2C13H4Cl235,35 was very close to zero (±0.0001), and it was not possible to determine its sign unambiguously. Using the negative value instead of the more likely positive value, a slightly different structure was obtained.
High-resolution measurements were carried out on the Cl nuclear quadrupole hyperfine structure in order to obtain the complete quadrupole coupling constant tensor in the C3H4Cl235,35 principal inertial axis system. The values obtained are χaa=—43.545 Mc, χbb=4.100 Mc, χcc=39.445 Mc, all ±0.005 and χab=—51.5±0.3 Mc. The principal quadrupole-coupling constant tensor elements are χα=—76.4±0.3 Mc, χβ=37.0±0.3 Mc, and χcc=39.445±0.005 Mc. The angle between the principal quadrupole axis component along the C–Cl bond and the C–Cl internuclear line is 0±15′. This is strong evidence against bent C–Cl bonds in this compound.
Detailed analysis of the Stark effect in the presence of quadrupole interaction leads to a dipole moment of 1.58 debye.
SCF-MO Wave Functions for the Hydrogen Fluoride Molecule
Authors: Clementi Enrico 
Published: January 2005

An SCF-LCAO-MO ground-state wave function is reported for the HF molecule at several internuclear distances. The basis set of Slater-type orbitals (STO's) was chosen so as to obey the following four criteria: (a) be a balanced basis set, i.e., each atom should have a set of STO's equally extended relative to the number and kinds of occupied AO's in the free atom; (b) include in the set STO's for a balanced polarization; (c) optimize the orbital exponents; (d) avoid redundancy in the set. The computed total energy at the internuclear distances of 1.7328 a.u. is —100.05804 a.u. This should be about 0.004 a.u. above the Hartree-Fock energy of the HF molecule. The significance of the STO's in the basis set adopted is illustrated by several parallel computations. The computed equilibrium distance is 1.74 a.u. and the experimental is 1.733 a.u. The dipole moment is computed for several wave functions and the value corresponding to the best wave function is 1.984 D (experimental is 1.74 D), whereas the best computed moment for another wave function is 1.970 D. The significance of this variation is discussed. The dμ/dr is estimated at 1.7 D/a.u. at the equilibrium distance (experimental is 0.954). The overlap population and gross charge Q are computed for several internuclear distances. The significance of the QH is discussed; the best value of QH at the internuclear distance is 0.479.
The ground-state 2Π and the excited-state 2Σ+ for HF are investigated. An SCF computation is made for the 2Π+ excited state at several internuclear distances. Gross charges and overlap populations are given for different internuclear distances for the two ionic states. The reorganization effect due to the removal of one electron is discussed in relation to the total energy, population analysis, and gross charge QH for the ion. A discussion of the computed ionization potential I(3σ) is given at the end of the paper.
Mass Spectrometry of the HO2 Free Radical
Authors: Foner S. N. , Hudson R. L. 
Published: January 2005

Mass spectrometric studies on the production, identification, and determination of thermochemical energies of HO2 radicals are reported. Reactions found to produce HO2 radicals, and examined in some detail, were: (1) reaction of H with O2, (2) reaction of H with H2O2, (3) reaction of O with H2O2, (4) reaction of OH with H2O2, (5) photolysis of H2O2, and (6) low-power electrical discharge in H2O2. Of the reactions studied, the low-power electrical discharge in H2O2 provided the most intense and convenient source of HO2 radicals. Ion—molecule reactions, which are negligible in normal operation of our mass spectrometer, are shown to be a potentially serious source of interference in studies of HO2 with conventional mass spectrometers.
The ionization potential of HO2, I(HO)2, and the appearance potential of HO2+ from H2O2, A(HO2+), have been redetermined, and the bond dissociation energies D(H–OOH) and D(H–O2) have been recalculated. The measured values are: I(HO2) = 11.53±0.02 ev, A(HO2+) = 15.36±0.05 ev with an estimated absolute accuracy of ±0.1 ev. The derived thermochemical energies are: D0(H–OOH) = 88.4±2 kcal/mole, D0(H–O2) = 45.9±2 kcal/mole, ΔH00(HO2) = 5.7±2 kcal/mole for the values at 0°K; and D(H–OOH) = 89.6±2 kcal/mole, D(H–O2) = 47.1±2 kcal/mole, ΔH2980 (H–O2) = 5.0±2 kcal/mole for the corresponding values at 25°C. Possible sources of error are examined and their effect on these values is discussed.
Pulse Radiolysis Studies. I. Transient Spectra and Reaction-Rate Constants in Irradiated Aqueous Solutions of Benzene
Authors: Dorfman Leon M. , Taub I. A. , Bühler R. E. 
Published: January 2005

The radiation chemistry of aqueous benzene solutions has been studied by the electron-pulse radiolysis technique. Ultraviolet absorption spectra of some of the transient species have been recorded by synchronized flash-absorption spectroscopy. The elementary reactions occurring have been observed by fast photoelectric recording of the transient optical density.
A transient spectrum having a broad absorption with a strong maximum at 313 mμ has been observed. On the basis of both spectrographic and kinetic evidence this spectrum is assigned to the hydroxycyclohexadienyl radical, (OH)C6H6·. The molar extinction coefficient is estimated to be ε3130=3500±800 M—1cm—1. A number of substituted cyclohexadienyl radicals have been observed in aqueous solution as well as in pure benzene and chloro-benzene. A second transient observed in oxygenated aqueous benzene solution shows an absorption shifted to lower wavelengths. This is attributed to the hydroxycyclohexadienyl peroxy radical, (OH)C6H6O2·.
Absolute rate constants have been determined at 23°C for the following reactions: OH+C6H6=(OH)C6H6·(4.3±0.9)×109 M−1sec−1,OH+C6D6=(OH)C6D6·(4.7±0.9)×109 M−1sec−1,(OH)C6H6·+O2=(OH)C6H6O2·(5.0±0.6)×108 M−1sec−1.
The yield of phenol in oxygenated solution was found to decrease continuously with increasing pulse intensity. At the highest intensity used, G(C6H5OH) = 0.19 molecules/100 ev. At the lowest pulse intensity used, G(C6H5OH) = 1.9 molecules/100 ev, which approaches the values found in steady irradiations. Some additional phenol is formed in slow post-irradiation reactions. Diphenyl was identified as a product in the deaerated system by gas chromatographic analysis. Its formation is largely the result of post-irradiation reactions, the initial yield being substantially lower than previously reported.
The mechanism of the radiation chemical reaction in both deaerated and oxygenated solutions is discussed on the basis of the conclusion that the hydroxyl radical enters the ring to form the hydroxycyclohexadienyl radical.
NMR Study of the Protolysis Kinetics in Simple Amino Acids. I. Sarcosine Hydrochloride and its Ester
Authors: Sheinblatt M. 
Published: January 2005

The mean lifetime of the amino group τ of acidic aqueous solutions of sarcosine hydrochloride and sarcosine methylester hydrochloride were measured using the NMR technique at 21±1°C. The experimental results show:
(1) 1/τ is first order in respect to both sarcosine and its ester concentration.
(2) 1/τ depends strongly on 1/aH+ in very acidic solutions and becomes almost independent in dilute acid solution. The interpretation is given in terms of an exchange of protons between the amino acid or its ester with a water molecule which is hydrogen bonded to the amino group. The exchange mechanism involves two steps:[Complex chemical formula][Complex chemical formula]Values of the rate constants for sarcosine hydrochloride are: kI′=110(sec−1),  k−I′=3.2×1010(sec−1M),  kH=8.3×109(sec−1);and for sarcosine methyl ester are: kI′=120(sec−1),  k−I′=3.2×1010(sec−1M),  kH=1.9×1010(sec−1).
Sixth and Seventh Virial Coefficients for the Parallel Hard-Cube Model
Authors: Hoover William G. , De Rocco Andrew G. 
Published: January 2005

A procedure for calculating virial coefficients for parallel hard lines, squares, and cubes is outlined, and the sixth and seventh virial coefficients are computed for these models. The essential step in the evaluation of the star integrals lies in the recognition of the fact that only a few ``subintegrals'' contribute to each virial coefficient, relative to the total number of labeled star integrals. Both the sixth and seventh virial coefficients are negative for hard cubes, a fact interesting from the point of view of phase transitions. Approximations to the excess entropy are given for squares and cubes.
The procedure for the star integrals is extended to the calculation of approximations to the pair distribution function and the potential of the mean force. These functions are calculated through the fourth approximation for hard lines, squares, and cubes.
The topological graphs needed for the above investigations, together with the values of the related integrals in one dimension, are displayed.
Effect of Adsorbed Phases on the Electrical Conductivity of Synthetic Crystalline Zeolites
Authors: Stamires Dennis N. 
Published: January 2005

The electrical conductivity of Linde synthetic crystalline zeolites type X and type A has been measured as a function of various adsorbed phases in the crystals. The potential energy barrier for the conduction process is decreased by the interaction of the adsorbed molecules with the electrostatic field or the field gradient in the lattice. Polar molecules, such as water and ammonia, exhibit a strong association through ion-dipole interactions with the most mobile cations.
The mechanism of adsorption of various molecules and the self-diffusion of sodium ions in these phases at discussed in terms of changes in the activation energy, free energy, and entropy of the conduction process. The relative importance of the electrostatic, dispersion, and quadrupole contributions to the interaction energy of the adsorbate with the zeolite is described.