bluuebunny/crossref_metadata_2025_split huggingface dataset:
Vibrational Spectrum and Structure of Metal-Cyanide Complexes in the Solid State. III. Hg(CN)2
Authors: Jones Llewellyn H. 
Published: January 2005

The infrared spectra of solid Hg(CN)2 and the mono- and di-substituted C13 and N15 species have been observed. The polarized spectrum of a single crystal of the normal species was also observed. The seven fundamental vibrations of the linear, symmetric Hg(CN)2 molecule have been assigned at 2192, 415, 2193.5, 442, 276, 341, and ca 100 cm—1.
From the observed frequencies of the normal and isotopic species, force constants were calculated for two possible structures: N–C–Hg–C–N and C–N–Hg–N–C. It is shown that the latter structure gives unreasonably large values for the CN stretching force constant (&gt; 20 md/A) and the CN, HgN interaction constant (∼2.4 md/A), while the former structure yields quite reasonable force constants, namely: Fcn=17.6, Fhgc=2.61, Fcn, c′n′=—0.1, Fhgc, hgc′=0.1, and Fhgc, cn=0.1 md/A. These results are presented as strong evidence that the cyanides are bound to the mercury through carbon atoms.
Thermal Exchange of Iodine with Methyl Iodide and with Hydrogen Iodide in the Gas Phase
Authors: Schmied Henry , Fink Richard W. 
Published: January 2005

The thermal exchange of iodine with CH3I and with HI has been studied in the gas phase between 60° and 140°C. The exchange is strongly surface sensitive and follows the rate law: R=k1(CH3I)(I2)+k2(CH3I). The exchange proceeds by means of two competing mechanisms, one of which is independent of iodine concentration and possibly involves the formation of CH3· free radicals on the surface which then react with I2. This heterogeneous reaction may be eliminated by preheating the reaction vessel overnight at 550°C, which reduces the reaction to a simple bimolecular exchange following the rate law: R=(CH3I)(I2)(2.5×106)exp(−9000/RT) moles−cm−3−sec−1which was obtained specifically for a surface/volume ratio of 1.19 cm—1.
The formation of a complex between CH3I and I2 was studied spectrophotometrically in dry n-heptane. The heat of formation of the complex was found to be —4.5 kcal mole—1, and the entropy of formation was found to be —25.8 cal deg—1 mole—1 for a standard state of 1 mole-liter—1. The formation of a complex between HI and I2 also was established in dry n-heptane.
The gaseous exchange of HI with I2 was found to be so fast that kinetic data could not be obtained. A theoretical estimate of the exchange half-life assuming an atomic iodine mechanism shows that the reaction would be rapid; however, experimental evidence is presented which suggests that a bimolecular mechanism is more likely.
Argon Adsorbed on a Graphitic Surface. The Heat of Adsorption from Lattice Liquid Theory
Authors: Pace E. L. 
Published: January 2005

A model is proposed to account for the differential or isosteric heat of adsorption which has been observed for argon on graphon at concentrations between 0.5 and 2.0 monolayers for temperatures in the neighborhood of the normal boiling point of argon.
The energy of a molecule on the surface is considered to be the sum of two contributions: (1) a site energy for the isolated molecule and (2) an interaction energy with neighbors in the same layer. The site energy for a molecule is calculated assuming atoms and molecules in lower layers fixed with respect to both a configuration in a hexagonally packed planar lattice and the distance between layers. The interaction energy is calculated assuming the behavior in any layer is represented by a two dimensional lattice liquid model utilizing the so-called Ono approximation for the variation of the generalized free volume with vacancies in the lattice. The distribution of adsorbed molecules in any layer is considered to be completely random.
On the basis of this model, an interpretation is made of the two maxima in the isosteric heat which have been observed experimentally.
Configuration Interaction Study of the Electronic Structure of the OH Radical by the Atomic and Molecular Orbital Methods
Authors: Freeman A. J. 
Published: January 2005

The role played in configuration interaction calculations by the particular form of the orbitals selected as basis is explored by a direct application on the electronic structure of the ground state of the OH molecule. Two configuration interaction studies have been carried out using different sets of one-particle functions: (1) the set natural to the isolated atoms (called AO's) and (2) the orbitals belonging to the molecule (MO's).
In (1), using the Hartree-Fock 1s, 2s, and 2p functions for atomic oxygen and the 1s state for hydrogen, and keeping the 1s oxygen state doubly occupied, all Slater determinants of the appropriate ground state symmetry (2π) were found. The dissociation energy and the expansion coefficients of the determinants were determined by a variational procedure which minimized the energy of the system. The nonorthogonality of the basic AO's was treated without approximation by the method of Löwdin. The necessary integrals were calculated on Whirlwind I, the M.I.T. high-speed digital computer; all two-center integrals were computed by expanding the hydrogen orbital about the oxygen center (analogously to the methods of Barnett and Coulson, Coolidge, Löwdin, etc.).
In (2), the molecular orbitals (MO's) were found as linear combinations of the above AO's, with coefficients determined by a modified self-consistent field (Roothaan) procedure, in which the energy of a single Slater determinant was made stationary at three values of the internuclear separation. A configuration interaction calculation was then made using these ``best'' MO's as the basic set of one-particle functions. Also included are a calculation of the dipole moment and Mulliken's electron distribution analysis.
The results of these studies are discussed and comparison is made to experiment and other theoretical calculations.
Chemical Bond. II. A One-Dimensional Approach to the Energetics and Ionic Character
Authors: Barrow Gordon M. 
Published: January 2005

One-dimensional counterparts of atomic bonding orbitals are given which allow, in the LCAO method, calculation of binding energies and electronic distributions for single bonds between atoms of various electronegativities. The bond energies and ionic characters so calculated are shown to be in satisfactory agreement with the values observed for a number of bonds. Predictions are then made of the ionic character of a bond as a function of electronegativity difference and bond length.
The potential usefulness of the approach is stressed in terms of the simplicity of the model and of the calculations and the essential correctness of the theoretical results.
Microwave Spectrum of Methyl Difluorosilane
Authors: Swalen J. D. , Stoicheff B. P. 
Published: January 2005

The microwave spectra of five isotopic species of methyl difluorosilane (CH3SiHF2) have been observed. From the rotational constants, the following structural parameters were determined rFF=2.541±0.001 ArSiC=1.833±0.002 A∠FSiF=106∘44′±30′rSiF=1.583±0.002 A∠;CSiH=116∘10′±1∘rSiH=rSiD=1.474±0.005 A∠FSiC=109∘52′±30′rCH=1.09 A (assumed)∠HCH=108∘ (assumed).A dipole moment of 2.11 debye was obtained from Stark effect measurements.
The hindered internal rotation of the methyl group splits some of the rotational lines into doublets with spacings from 0.5 to 2.9 Mc. An analysis of the doublet splitting in three of the isotopic species gives a barrier height of 439 cm—1 (1255 cal/mole) hindering internal rotation.
Heat Capacities of CrF3 and CrCl3 from 15 to 300°K
Authors: Hansen Wilford N. , Griffel Maurice 
Published: January 2005

The heat capacities of CrF3 and CrCl3 have been measured over the temperature range from 15 to 300°K. CrF3 has two peaks; the upper peak has its maximum at 69.8°K and is associated with a known magnetic transition. The lower peak has its maximum at 45.6°K and has not been correlated with magnetic phenomena. The total magnetic entropy is divided almost equally between the two. CrCl3 has a single peak at 16.8°K which is associated with a ferromagnetic transition.
For CrF3, S298.150=22.44 eu; for CrCl3, S298.150=29.38 eu. Other thermodynamic functions are tabulated.
Evaluation of Lattice Interactions in or near a Cubic Crystal
Authors: Durham George S. , Soderberg Barbara A. 
Published: January 2005

Procedures, based on the methods of Madelung, have been developed for the evaluation of lattice sums of inverse-power particle-interactions, λa—n, at any point in or near a cubic crystal. Although not as elegant mathematically as those of Hove and Krumhansl, they are more complete in including the important cases of a point near a plane or line of particles, and are sufficiently simple in principle to be understood and applied by anyone with a background in differential calculus.
Applications to a face-centered cubic ionic crystal are discussed and, as an example, the dipole-dipole van der Waals energy of a chloride ion before a NaCl half-crystal is calculated.
Study of the NH Radical by the LCAO-SCF Molecular Orbital Method
Authors: Boyd Marjorie E. 
Published: January 2005

Wave functions, orbital energies, and total molecular energies have been obtained for the ground and five excited states of the NH radical. The Roothaan method was used, modified for the case of a molecule with unfilled orbitals. Separate self-consistent procedures were carried out for the ground state and a doubly excited state, while results for the intermediate excited states could be calculated with the ground state orbitals. Dissociation energies, dipole moments, and electron population analyses were also computed.
Comparison with the sparse experimental data indicates that the calculated states are too widely separated in energy. It is also found that this complete treatment gives higher energy values than Higuchi reported in an incomplete computation employing various approximations, although the wave functions are little changed.
In general, results seem to be about as reliable for the diatomic open shell case as for the usual closed shell molecules. Contrary to Sahni's suggestion, they do not appear to be better for the heteronuclear than for the homonuclear case.
Electron Spin Resonance in Transition Metal Chelates. I. Copper (II) Bis-Acetylacetonate
Authors: Maki A. H. , McGarvey B. R. 
Published: January 2005

Electron spin resonance at 3.2 cm has been observed from copper(II) in single crystals of copper(II) bis-acetylacetonate diluted to ½ mole % with palladium(II) bis-acetylacetonate at 77°K and 300°K. The parameters of the spin Hamiltonian have been expressed in terms of the atomic orbital coefficients of molecular orbital wave functions describing the electron hole in the orbital ground state and two excited states. Experimental determination of the spin Hamiltonian then results in expressions for the molecular orbital wave functions. The results indicate that the in-plane sigma and pi bonding are appreciably covalent, whereas the out-of-plane pi bonding with the acetylacetonate ring is ionic.
The hyperfine interaction may be expressed by a relation of the type K2g2=A2g∥2cos2θ+B2g⊥2sin2θ+2C2g∥g⊥sinθcosθ, where C2 increases with decreasing temperature. The appearance of the term in sinθ·cosθ is attributed to low symmetry crystal fields due to the crystallographic array, the main symmetry being determined by the molecule itself. A small amount of rhombic character was observed in the g tensor, but was not enough to make an accurate location of the gx and gy directions possible. For the purpose of analysis, the g factor is expressed in terms of the two principal values g∥ and g⊥ which do not vary between 77°K and 300°K to the accuracy of the determination.
Generalized United-Atom Theory of Molecules. I. Spherical Contributions in the sσ Wave Functions for H2+
Authors: Chen Tien Chi 
Published: January 2005

The generalized united-atom view of molecules suggests that electronic states of symmetric molecules may be characterized by means of ``atomic'' quantum numbers.
A test for the purity of the quantum number l in sσ states in H2+ is facilitated by the Tibbs-Wannier theory of a Coulomb field with cutoff. Comparison shows that 96% of the ground-state electronic energy is due to contributions of spherical functions.
Kinetics of Decomposition of Isobutyryl Peroxide and Reactions of Isopropyl Radicals
Authors: Smid J. , Szwarc M. 
Published: January 2005

The kinetics of decomposition of isobutyryl peroxide was investigated in isooctane solution. The decomposition was shown to be unimolecular, the activation energy being 27.3 kcal/mole and the frequency factor 2.8·1014 sec—1. The lower activation energy of this decomposition, as compared with decompositions of other acyl peroxides, suggests that energy is supplied to the O–O bond by the decarboxylation of radicals resulting from the dissociation of this peroxide. The problem of energy supply is taken further in the following publication.
The reactions of isopropyl radicals formed in the dissociation process were studied quantitatively.
Vibrational Spectra of the Crystalline Methyl Halides
Authors: Dows David A. 
Published: January 2005

The infrared spectra of the crystalline methyl halides, CH3Cl, CH3Br, and CH3I, at 80°K are reported. Information on gas-solid frequency shifts, band splittings due to site symmetry and intermolecular coupling, librational frequencies, and relative intensities of band components is summarized and compared.
Relative intensities of band components are not in agreement with the predictions of the ``oriented gas'' model. Most other observations are consistent with the assumption of isomorphism between the crystal structures of the three compounds, but the data are not sufficient to prove the isomorphism.
Internal Barrier of Propylene Oxide from the Microwave Spectrum. II
Authors: Herschbach Dudley R. , Swalen Jerome D. 
Published: January 2005

Several long progressions of perpendicular transitions have been measured in the microwave spectrum of propylene oxide. These have provided an opportunity to test the theory of internal rotation over a very large range of rotational quantum numbers, J=1 to 48 and K=1 to 25, in the ground torsional state. For low K, the K doubling which arises from the asymmetry of the molecule is much larger than the splittings due to tunneling through the potential barrier. The spectrum resembles that of an ordinary asymmetric rotor except that each line is split into a close doublet by the tunneling. At high K, the K doubling becomes negligible. A triplet fine structure is observed in which the spacings show a periodic dependence on K, essentially the same as that calculated for the case of two coaxial symmetric tops. (For a true symmetric rotor, the selection rules would prevent the observation of this pattern.) At intermediate K, the K doubling and the tunneling perturbations become comparable. The mixing of the rotational wave-functions which results permits ``forbidden'' lines to appear. Very good agreement with theory is obtained over the whole range of K, with the barrier height V3=895 cm—1 (2560 cal/M).
Rotational transitions have also been assigned for molecules in the first and second excited torsional states, in which the tunnel effect splittings are greatly magnified. For both the excited states, the barrier height is found to be identical with the ground state result. This supports the usual assumption that perturbations from vibrational interactions with internal rotation and from the sixfold V6 term in the potential barrier are small enough to be safely neglected.
Random Events in a Liquid
Authors: Turner R. E. 
Published: January 2005

A model is suggested for the evaluation of the time integral of the autocorrelation function for inter-molecular forces. This integral plays the part of a ``friction constant'' in the statistical mechanical theory of transport processes.
A cluster of a small number of molecules is regarded as a nonisolated system. By using a self-consistency principle i.e., the identity of the autocorrelation function for all molecules, a fourth-order differential equation is derived, which in principle could be made to give a unique determination of the autocorrelation function. Two methods are given for finding an approximate solution.
An alternative expression for the autocorrelation function is found by the introduction of ``collective'' coordinates. Comparison of this expression with the result obtained by the principle of self-consistency leads to a unique determination of the integral of the autocorrelation function.
The result has a reasonable physical interpretation for the mechanism of correlation breakdown, namely, the transfer of energy from ``collective'' motion or sound waves to ``individual'' or ``average'' motion.
Crystal Structure of Copper Fluoride Dihydrate, CuF2·2H2O
Authors: Geller S. , Bond W. L. 
Published: January 2005

The crystal structure of copper fluoride dihydrate, CuF2·2H2O, has been determined from single crystal x-ray data. The monoclinic unit cell, space group C2h(3)—12/m, with a=6.416, b=7.397, c=3.301, all ±0.005 A, β=99.6±0.1°, contains two formula units. The atoms are in the following positions: Cu(II) in 2(a): (0, 0, 0; ½, ½, ½): F— in 4(i): (0, 0, 0; ½, ½, ½)±(x, 0, z) with x= —0.222, z=0.311; O in 4(g): (0, 0, 0; ½, ½, ½)±(0, y, 0) with y=0.261. The estimated parameters of the H atoms in 8(j): (0, 0, 0; ½, ½, ½)±(x, y, z; x, y, z) are x=0.107, y=0.340, z= —0.073. In this structure the Cu(II) atoms have two fluorine neighbors at 1.89 A, two (water) oxygen neighbors at 1.93 A, and two fluorine neighbors at 2.47 A. These form a highly distorted octahedron about the Cu(II), and in fact, the distance of the two further fluorine atoms implies that the Cu(II) prefers square coordination. The distance 2.66 A between an oxygen and a fluorine associated with a neighboring lattice point implies appreciable hydrogen bonding between these atoms .Comparisons are made with other Cu(II) halide compounds and the observed antiferromagnetism is discussed.
The morphology and optic axes have been investigated. The refractive indices (NaD) are α=1.51, β=?, γ=1.54. The optic angle 2V≅46° and the optic axes lie in the (010) plane between +a and +c, one optic axis making an angle of 16° with the c axis.
Effect of Pressure on the Spectra of Certain Transition Metal Complexes
Authors: Parsons R. W. , Drickamer H. G. 
Published: January 2005

The effect of pressure (to 130 000 atmospheres) has been measured on the splitting of the 3d levels of the nickel and chromium ions complexed with water and ammonia. Data have also been obtained on CoSO4· 7H2O and K3Fe(CN)6. In general, the effect of pressure is to increase the effect of the ligand field and to increase the splitting of the levels. This is interpreted in terms of the change in ligand-metal distance. A phase transition was noted in [Ni(H2O)6]SO4 at 65 000 atmospheres.
A charge transfer band was also observed in [NiNH3)6]Cl2. The effect of pressure is to increase the intensity with no apparent change in the location of the maximum.
Energy Levels, Atom Populations, Bond Populations in the LCAO MO Model and in the FE MO Model. A Quantitative Analysis
Authors: Ham Norman S. , Ruedenberg Klaus 
Published: January 2005

Quantitative results for fourteen representative organic molecules are derived and analyzed on the basis of the LCAO MO model and on the basis of the FE MO model. Calculated are, besides the energy levels, the atom populations and the bond populations, quantities defined in a recent paper as an accurate measure of the distribution of electrons.
The results of the LCAO MO model and of the FE MO model are then compared, and for the more important quantities considerable agreement is found. The origin of the agreements and disagreements is shown to be different from the one generally supposed.
Because of their general usefulness, complete tables are given for the eigenvalues and eige nvectors of the fundamental topological matrices associated with the molecules investigated.
Physical Adsorption on Non-Uniform Surfaces
Authors: Halsey George 
Published: January 2005

Analysis of adsorption on a uniform surface using the quasi-chemical theory of interaction shows that the hypotheses of the BET theory lead to substantially no adsorption beyond the first layer if E2 = EL, and stepwise isotherms if E1&gt;E2&gt;E3&gt;···&gt;EL. For the monolayer adsorption of gases on silver, platinum, and steel, the heterogeneous nature of the adsorbing surface is clearly indicated. Cooperative adsorption on the non-uniform surface is treated, and the cooperative analog of the Freundlich equation derived. The typical multi-layer isotherm is shown to be composed of three regions: non-cooperative adsorption on a strongly heterogeneous surface; cooperative adsorption on a still heterogeneous surface; and cooperative multi-layer adsorption induced by small van der Waals perturbations some distance from the surface.
The isotherm p/p0=exp{—a/θr} is derived and shown to be a good representation of adsorption data that conform to the BET Type I, II, or III shapes.
The Mercury Photosensitized Reactions of Isobutene
Authors: Allen G. A. , Gunning H. E. 
Published: January 2005

An investigation has been made of the reaction of isobutene with mercury (3P1) atoms at 30°C. Acetylene and propylene have been shown not to be among the main products of the reaction. The over-all rate of consumption of isobutene and the rate of pressure decrease both decrease with increasing initial pressure in the complete quenching region. These rates approach constant values for initial pressures of 180 mm and higher The results of this investigation show that isobutene behaves similarly to the other olefins in reacting with mercury (3P1) atoms at 30°C, in that the reactions can be explained by the following initial steps for the mechanism: i−C4H8+Hg(3P1)→i−C4H8*+Hg(1S0)i−C4H8*+i−C4H8→2i−C4H8,accompanied by the decomposition of the activated isobutene molecule into reaction-initiating fragments.
The discrepancies between the results of this investigation and those of the earlier work of Gunning and Steacie may be due to the effect of impurities in the original isobutene, since it is shown that small amounts of added propylene or acetylene change the rate of reaction markedly.
Statistical Mechanics of Multimolecular Adsorption. IV. The Statistical Analog of the BET Constant a1b2/b1a2. Hindered Rotation of a Symmetrical Diatomic Molecule Near a Surface
Authors: Hill Terrell L. 
Published: January 2005

An approximate study is made of the restricted rotation of a symmetrical diatomic molecule near a surface. This makes possible some calculations concerning the BET constant C=R exp(ε1—Λ)/kT, and especially the factor R (which is customarily set equal to unity). Cassie has pointed out that if this factor is set equal not to unity but to about 1/50 or even less, the low values of the heat of adsorption usually found on putting R=1 in the analysis of data are accounted for. The results obtained here indicate, unfortunately, that this factor is of the order of, say, 5–10, and that another explanation of the low heats of adsorption mentioned above will have to be found. An alternative method of estimating the area occupied per molecule in a completely filled monolayer is mentioned in an appendix.
The temperature dependence of the quantity R is of some experimental interest, and a brief discussion of this dependence as predicted by the present approximate treatment is included.