bluuebunny/crossref_metadata_2025 huggingface dataset:
Infrared Spectra of Foreign Molecules in Beryl
Authors: Wood D. L. , Nassau K.
Published: January 2005

Thirty infrared absorption lines in beryl between 1500 and 11 000 cm−1 are assigned to vibrations of two types of water and to CO2 all in the axial voids of the structure. The spectrum of Type-I water arises from molecules which are capable of libration and are located between the silicate rings which make up the crystal. The spectrum of Type-II water arises from molecules in the same sites, but with alkali ions nearby. These molecules are also capable of libration, but at a higher frequency. The Type-I molecules have their C2 symmetry axes perpendicular to the crystal C6 axis, while the Type-II molecules have their symmetry axes aligned parallel to the crystal C6 axis. The CO2 molecules are oriented with their long axes prependicular to the crystal C6 axis. Modification of the spectra by heat and hydrothermal treatments was not feasible and the identity of the alkali ions apparently does not influence Type-II spectrum.
Further Applications of the Domain Theory of Liquid Water: I. Surface Tension of Light and Heavy Water; II. Dielectric Constant of Lower Aliphatic Alcohols
Authors: Jhon Mu Shik , Van Artsdalen E. R. , Grosh Joseph , Eyring Henry
Published: January 2005

Recently, Jhon, Grosh, Ree, and Eyring used the significant-structure theory to explain all the thermodynamic and transport properties of water, assuming that it contains domains of about 46 molecules which change their structure as a unit from an ``ice I-like'' to an ``ice III-like'' state. Following this, Hobbs, Jhon, and Eyring explained the dielectric constant of liquid water. According to their theory, an applied field will make those domains grow which are favorably oriented with respect to the field at the expense of the less favorably oriented until a steady state is achieved. This domain theory of liquid water has been applied to several cases. Surface tension of liquid water has been successfully calculated in good agreement with experiment applying the generalized method of Change et al. Assumptions were made that the molecules in the top layers are in an asymmetric field and tend to orient in the direction of the field. This leads to continuous changes in the density for the various layers. The calculation of the dielectric constant of various alcohols was carried out by a similar scheme to that used for liquid water, and the effect of the G factor in the formula has been discussed.
Electron Spin Resonance in Single Crystals of Anhydrous Copper Sulfate
Authors: Wells J. S. , Matarrese L. M. , Sukle D. J.
Published: January 2005

The magnetic resonance of synthetic anhydrous copper sulfate has been investigated at 23.3 GHz at temperatures between 77°K and 4.1°K. In the paramagnetic region, the observed resonance consists of two lines. One of these is relatively narrow and remains essentially fixed even down to 4.1°K. The second line is unusually broad and its behavior indicates that it is due to the copper ions in the anhydrous crystal. The g values and corresponding linewidths have been measured for the broad line at 77°K. As the temperature drops to the Néel point, this broad line increases in width, then shifts, and disappears rather rapidly, indicating that it is associated with the antiferromagnetic phase.
Study of Collision-Induced Phenomena with a Dempster Mass Spectrometer. I. Theoretical
Authors: Harris Harold H. , Russell M. E.
Published: January 2005

Utilizing the natural focusing characteristics of the Dempster mass spectrometer, equations are derived for the measurement of cross sections for collision-induced reactions and for total collision cross sections.
Improvement of Uncoupled Hartree-Fock Expectation Values for Physical Properties. II
Authors: Epstein S. T. , Johnson R. E.
Published: January 2005

A comparison is made between approximate polarizabilities calculated in the coupled Hartree-Fock approximation with those obtained from the uncoupled Hartree-Fock approximation with first-order corrections.
Thermal Electron Escape in Irradiated Dipolar Systems
Authors: Schiller Robert
Published: January 2005

The possibility of thermal electron escape from the neighborhood of positive ions is studied from the point of view of the change of free energy. On the basis of a generalized spur (track) model a sufficient condition is formulated for the decrease of free energy in electron escape. This condition is fulfilled in every system if the electron-electron repulsion is high, or in polar systems if the diffusing electrons are not too fast. Short dielectric relaxation time and large difference between static and infrared dielectric constants increase the escape probability.
Chlorine and Antimony Nuclear Quadrupole Resonance in SbCl5CH3CN, SbCl5POCl3, and SbCl5
Authors: Schneider Robert F. , DiLorenzo James V.
Published: January 2005

Nuclear quadrupole resonances due to 121Sb, 123Sb, Cl35, and 37Cl have been observed in SbCl5POCl3, SbCl5CH3CN, and SbCl5 at a number of temperatures. The resonances in SbCl5POCl3 are correlated with the known structure of that complex. A covalent structure for the SbCl5CH3CN complex is proposed on the basis of its resonances. A phase change in SbCl5 occurs between 195° and 210°K. At 210°K and above the Sb resonances are consistent with a trigonal bipyramidal structure and the chlorine resonances are not visible. At 195°K and below the resonances of Sb and Cl indicate a complex structure. A bridged dimeric structure similar to that in NbCl5 is suggested. A discussion of relative intensity measurements is included. A qualitative discussion of the temperature dependences and their implications on the molecular dynamics of these molecules is also included.
Effects of Molecular Motions on the Nuclear Quadrupole Resonance Frequencies and Linewidths in Some Solid Alkyl Halides
Authors: Tokuhiro Tadashi
Published: January 2005

Temperature dependences of the halogen nuclear quadrupole resonance frequencies and the linewidths have been studied in solid CH2ClCH2Cl, CD2ClCD2Cl, CH3I, CD3I, and CH3Br. Dependences of the frequencies in these molecules can be explained by Bayer's effect on the field gradient. The cause of remarkable increases in linewidths and the mechanism of the hindered rotation around the long axis in CH2ClCH2Cl and CD2ClCD2Cl have been discussed by comparing the values of the potential barrier which hinders the reorientational motion. The changes in the doublet structures of bromine and iodine resonances in CH3Br, CH3I, and CD3I with rising temperature have been considered in view of the influence of the reorientation around the symmetry axis of surrounding molecules on the field gradient to which the nucleus of interest experiences. From the temperature dependence of the bromine resonance frequency in CH3Br, the average temperature coefficient of the B-axis torsional vibrations has been obtained and the heat capacity of solid CH3Br under constant pressure has been calculated by using this value.
Vibrational Relaxation with a Lennard-Jones Potential
Authors: Hartmann Bruce , Slawsky Zaka I.
Published: January 2005

Numerical calculations on vibrational relaxation in chlorine are presented. A Lennard-Jones potential is used, and the results are compared with the results of the Schwartz-Slawsky-Herzfeld (SSH) theory, which uses a shifted exponential potential. Approximate wavefunctions of the Airy function form are shown to be sufficiently accurate for the calculation of the transition matrix elements. The SSH analysis of the effect of attractive forces is shown to be valid. There is a significant difference between the results for the exponential and for the Lennard-Jones potentials, with the exponential giving better agreement with experiment.
Magnetic and Optical Spectra of Copper Monochloroacetate 2.5 Hydrate
Authors: Kokoszka Gerald F. , Allen H. C. , Gordon Gilbert
Published: January 2005

The electron paramagnetic resonance spectra of copper monochloroacetate 2.5 hydrate, Cu(O2CCH2Cl)2·2.5H2O, [Cu(ClAc)2], and zinc-doped Cu(ClAc)2 have been observed at both K-band and X-band frequencies. The EPR spectrum of the pure material was characteristic of a species with a spin of one, while the spectrum from zinc-doped Cu(ClAc)2 revealed an additional spectrum due to a species with a spin of ½. The g values for both the copper—copper pairs and the copper—zinc pairs were identical with values gz=2.38 and gx=gy=2.07. The hyperfine coupling constant for the copper—copper pairs was about 84×10−4 cm−1, while in the copper—zinc spectrum it was about 158×10−4 cm−1. These results are consistent with the assumption of a weakly coupled interaction. The temperature variation of the doubly integrated intensity of the derivative spectrum indicated that the triplet state lies some 230 cm−1 above the singlet ground state. In the optical absorption spectrum of Cu(ClAc)2 three bands were observed. A very intense band was found at 14 000 cm−1, while two other bands were centered at 11 000 cm−1 and 26 000 cm−1.
Surface Ionization. I. Desorption of U+ Ions from W and Re Surfaces
Authors: Hertel G. R.
Published: January 2005

The mean residence times (τ) of U+ ions on polycrystalline W and Re surfaces have been measured as functions of the surface temperature. The U+ desorption parameters that were determined from the relationship 1/τ=ω0 exp[—Ei/kT] are       Surfaceω0(sec−1)Ei(eV)Clean W(3.2±1.5)×10157.50±0.09Contaminated W(1.9±1.5)×10136.29±0.17Clean Re(0.7±0.3)×10136.70±0.09Slightly contaminated Re(1.2±0.7)×10136.84±0.14.

The effect of oxygen contamination on the W surfaces was dramatic. The Re results were not as clear cut. In the temperature range where uranium oxide ions were abundant, the simple desorption mechanism is complicated by surface reactions. The resulting log(τ−1) vs T−1 relationship is complex and nonlinear.
Raman Intensity Study of Zn(II), Cd(II), and Hg(II) Thiocyanate Complexes in Aqueous Solutions
Authors: Taylor Keith A. , Long Thomas V , Plane Robert A.
Published: January 2005

Raman spectra of the tetrathiocyanato complexes of Zn(II), Cd(II), and Hg(II) were measured in aqueous solution. Polarized Raman lines appear for SCN− at 747 and 2068 cm−1, for Zn(NCS)42− at 153, 817, and 2110 cm−1, for Cd(CNS)42− at ∼747 and 2098 cm−1, and for Hg(SCN)42− at 236, 717, and 2114 cm−1. The shift of the C–S frequency on complex formation is consistent with the binding of NCS− to Zn(II) through the N, to Hg(II) through the S, and to Cd(II) with some NCS− turned each way. Support for the proposed ambidentate binding to Cd(II) is given by the appearance in solutions having lower SCN− to Cd(II) ratios of lines characteristic of lower complexes showing separate frequencies characteristic of both S-bound and N-bound NCS−. Intensities of the various Raman lines were analyzed to give bond derived polarizabilities, which further support the different types of binding. Bonding of N to Zn causes a lowering of the C–N bond derived polarizability and an increase in that of the C–S. Strong sulfur binding by Hg(II) leads to a large value for the C–N bond derived polarizability while the value of this derivative for the Cd complex is intermediate between those of the Zn and Hg complexes and approximates that of free thiocyanate. The value of the derived polarizability for the C–S stretch of Hg complex is larger than is anticipated, but the magnitude in the Cd complex is identical with that of free thiocyanate.
Variation Principle Treatment of the Excluded-Volume Problem
Authors: Reiss H.
Published: January 2005

A variation principle is used to develop a ``single-segment'' self-consistent-field approach to the excluded-volume problem. The zeroth-order self-consistent field (based on freely orienting chain statistics) is computed. A partial differential equation is developed for the description of the ``random flight in a field'' problem emerging from the self-consistent-field approach. The appropriate boundary value problem is solved in one limit and the mean-square end-to-end distance for the polymer molecule is calculated. This is found to be proportional to L4/3, where L is the number of segments in the chain, a result which is in satisfactory agreement with earlier computer calculations. The end-to-end distribution going with the zeroth-order self-consistent field is found to be a displaced skew Gaussian.
Improvement of the Cluster-Variation Method
Authors: Kikuchi Ryoichi , Brush Stephen G.
Published: January 2005

It is shown that efficient convergence of the cluster-variation method (of cooperative phenomena in statistical mechanics) for the two-dimensional problem can be achieved by increasing the size of the basic cluster one dimensionally, rather than two dimensionally, and by formulating the degeneracy factor anisotropically. The method is illustrated with the Ising model in a square lattice, and the following are presented: (a) an angle-shaped (or a V-shaped) basic cluster of three points can give the same result as a square basic cluster; (b) a general case is formulated in which a zigzag shape of n V's is used as the basic cluster; and (c) the case of the W cluster (two V's) is calculated using the general formulation mentioned above. It is shown that, when they are plotted against the reciprocal of the number of points in a cluster, the Curie points calculated by different methods lie very close to a straight line.
Nonadiabatic Decomposition of N2O in the Deactivation of O(1D) by N2
Authors: Snelling David R. , Bair Edward J.
Published: January 2005

An extension of a flash-photolysis method described previously was used to measure the following absolute rate constants (all in liter per mole·sec): O(1D)+O3→2O2k2=2.0±1.0×1011,O(1D)+N2→O(3P)+N2k4a=1.3±0.6×1010,O(1D)+Xe→O(3P)+Xek4b=3.5±1.7×1010,O(1D)+Ar→O(3P)+Ark4c∼5×107.

The efficiency with which the O(1D)→O(3P) transition is induced by collisions depends specifically on the added gas. The results for deactivation by nitrogen are discussed in terms of the formation of an N2O* intermediate in a high level of vibrational excitation. Dissociation to N2+O(3P) at this energy level (85.2 kcal) is compared with thermal decomposition of N2O where predissociation to a state which correlates with O(3P) occurs at a lower energy level (〈ε〉=61.8 kcal).
Spatial Distribution of Trapped Electrons and Holes Produced by X Rays in KI(TlI)
Authors: Kaufman R. Gilbert , Hadley Wayne B.
Published: January 2005

When KI(TlI) is irradiated at 78°K, trapped electrons and holes are produced. Warming mobilizes the holes which either recombine to give light or are trapped to give new absorptions. Light sum and absorption measurements show that the ratio of retrapping to recombination (Rh) for holes is independent of the concentration of electron and hole centers. Bleaching in the ir frees trapped electrons which either recombine giving light or are retrapped. The relative quantum efficiency, which is a measure of the ratio of retrapping to recombination (Re) for electrons, is independent of the concentration of electron and hole centers. The stimulated electron recombination kinetics are first order with respect to concentration. From these facts it is suggested that the electron and hole are trapped near each other as a pair.
Noncombinatorial Method for Determining the Entropy of Lattices
Authors: Woodbury George W.
Published: January 2005

The composition law of information theory is considered in connection with lattice statistics. By the use of this law it is found that many of the standard exact and approximate results (exact solution of one-dimensional Ising model, Kramers—Wannier approximation, Bethe approximation, Bragg—Williams approximation and two hierarchies of approximations recently introduced by Kikuchi and Brush) can be obtained in a very direct manner, without reference to a combinatorial problem. A standard inequality of information theory is used to answer a question which has often arisen in connection with cluster variation methods—that is the question of why two seemingly different expressions for the free energy give the same results when the free energy is minimized. The branched Bethe and cactus lattices can be solved easily by means of the composition law. It is found that these lattice models can be interpreted in two different ways. For a hard-sphere lattice gas on one of these branched lattices, the two interpretations lead to very different behavior—in one case an order—disorder transition occurs and in the other case not.
ESR Evidence on Trapped Electrons and ``CO2−'' in γ-Irradiated 3-Methylpentane
Authors: Shirom M. , Claridge R. F. C. , Willard J. E.
Published: January 2005

The singlet ESR signal of γ-irradiated 3-methylpentane (3-MP) glass [K. Tsuji, H. Yoshida, and K. Hayashi, J. Chem. Phys. 46, 810 (1967)], which is attributable to physically trapped electrons, and the singlet and doublet resulting from reaction of electrons with CO2 [P. M. Johnson and A. C. Albrecht, J. Chem. Phys. 44, 1845 (1966)] in 3-MP glass have been examined further. Immediately after production by a 1019-eV g−1, 5-min γ dose, the electron line decays with an apparent half-life of less than 20 min. It is readily removed by illumination at 13 500 Å. ESR saturation is significant at 10−3 mW and prevents detection of the signal at powers above ∼1 mW. The ESR g value and the radiation G value are estimated to be ∼2.002 and 0.5±0.2, respectively. When 3-MP or 2-methyl-pentene-1 (2-MP-1) containing CO2 is γ irradiated at 77°K, a singlet (g=∼2.0007; linewidth=∼3.1 G) and a flanking doublet with a splitting of ∼8 G are produced. The singlet, but not the doublet, shows saturation effects starting at ∼0.05 mW. It may be removed by illumination of the sample at wavelengths of 4800 Å and below, producing new species, but is unaffected at 5500 Å and above. The initial ratio of the singlet to the doublet, the growth on standing at 77°K, and the rate of bleaching with ultraviolet light are sensitive to the amount of CO2 present. The observed radiation G value in samples containing 1 mole % CO2 and 99 mole % 3-MP, with a vapor—solid ratio of 8, is ∼0.3. The spectra are the same as those produced (Johnson and Albrecht) by photoionization of tetramethylparaphenylenediamine (TMPD) in 3-MP containing CO2 at 77°K.
Electron Spin Resonance of the Benzene Positive-Ion Radical
Authors: Carter Melvin Keith , Vincow Gershon
Published: January 2005

The benzene monopositive-ion radical C6H6+ is prepared by photoionization of benzene in a rigid sulfuric acid matrix. This highly symmetrical radical is of special interest because of the occurrence of near degeneracy in the vibronic levels. Electron spin resonance spectra are investigated over a range of temperatures. The hyperfine spacing is 4.44±0.01 G at −150°C and varies with temperature. The temperature coefficient of the total extent of the spectrum is −5.2±3 mG/°C (−110≤t≤−190°C). A computation of the benzene cation splitting using the semiempirical Colpa—Bolton equation [J. Chem. Phys. 43, 309 (1965)], which treats the effect of excess charge density on hyperfine splitting, leads to a value in fairly good agreement with experiment. The temperature dependence of the proton hyperfine splitting is discussed in terms of the expectation values of the Fermi contact interaction in the thermally populated molecular vibronic states. The g value observed for C6H6+ is 2.00242±0.00002. This result is compared with the g value computed from Stone's semiempirical equation [Mol. Phys. 6, 509 (1963); J. Chem. Phys. 43, 4191 (1965)]. Near degeneracy in hydrocarbon radicals is correlated with the occurrence of deviations from the predictions of Stone's equation.
Electron Spin Resonance of the Hexamethylbenzene and Hexaethylbenzene Positive-Ion Radicals
Authors: Carter Melvin Keith , Vincow Gershon
Published: January 2005

The hexamethylbenzene (HMB) and hexaethylbenzene (HEB) monopositive ions are prepared by chemical oxidation of the hydrocarbons in fuming sulfuric acid solution, and their electron spin resonance spectra are investigated. These highly symmetrical radicals are of considerable interest since they are expected to possess near spatial degeneracy. In the case of HMB cation g = 2.00266±0.00002 and the methyl-proton splitting is 6.53±0.01 G; for HEB cation g = 2.00261, the methylene splitting is 2.64±0.02 G (t=+2°C) and the methyl-proton splitting is 0.37±0.01 G. A program is written for computer simulation of ESR spectra and applied to the interpretation of the HEB cation spectrum. A small positive temperature coefficient is measured for the magnitude of the proton splitting of HMB cation in a rigid boric acid glass. The temperature coefficient of the methylene splitting in the spectrum of the HEB ion in solution is also positive but is an order of magnitude larger and varies significantly with temperature. Relative magnitudes of the HMB and HEB splittings and their temperature dependences are analyzed in terms of the effect of restricted rotation on alkyl-proton splittings. The Stone—Maki theory for the effect of hindered rotation on methylene-proton splittings [J. Chem. Phys. 37, 1326 (1962)] is programmed for the IBM 7094 computer and is modified to apply to the case of severely restricted motion. A simple harmonic-oscillator model with energy spacing 60±20 cm−1 reproduces the methylene splitting of HEB cation and its temperature coefficient reasonably well. The model fails to account for the temperature variation of the temperature coefficient. Reasons for this discrepancy are presented. Approximate quantum-mechanical calculations of the methyl-proton splitting are discussed. An HMO calculation with standard hyperconjugation parameters leads to the value 3.7 G for HMB cation. The g value of this radical is compared with the value predicted from Stone's semiempirical equation for hydrocarbon radicals [Mol. Phys. 6, 509 (1963)] and the discrepancy discussed. Linewidth variations in the spectrum of HMB cation in boric acid glass are reported.
Brillouin Scattering in Water: The Landau—Placzek Ratio
Authors: O'Connor C. Leonard , Schlupf Joseph P.
Published: January 2005

An experimental study of the ratio of intensities of the central line, in the molecular scattering of light, to the Brillouin components has been made in water over a temperature range from 0° to 50°C. A 75-mW He–Ne gas laser was used as a light source and the scattered radiation was analyzed by a pressure-scanned Fabry—Perot interferometer in conjunction with a dry-ice-cooled phototube detector with recorder output. The ultrahigh-frequency sound velocity is compared with values obtained by using ultrasonic techniques. There is no evidence of relaxation effects in the frequency range studied. An analysis of the Landau—Placzek ratio is made for water considered as an ideal fluid. It is shown that the usual approximations used in deriving the ratio (κT—κS)/κS are not valid for water. The actual behavior of the Landau—Placzek ratio for water as a function of temperature can be explained in part when an exact solution is used.
Dynamic Mechanical Properties of Concentrated Polystyrene Solutions at 40 MHz
Authors: Moore R. S. , McSkimin H. J. , Gieniewski C. , Andreatch P.
Published: January 2005

Measurements of dynamic shear impedance at 40 MHz and room temperature are reported for two polystyrene-solvent systems as a function of concentration. These measurements were made by an ultrasonic reflectance technique. The polymers had sharp molecular-weight distributions, M̄w/M̄n∼1.08, and molecular weights of 2.39×105 and 2.67×105. The concentrations ranged from about 1% to 20% and 3% to 30% in di-n-butyl phthalate, DBP (a near theta-solvent) and in toluene (a good solvent) for the two polymers, respectively. Results are reported in terms of the in-phase, G′, and out-of-phase, G″—ωηs, components of the dynamic shear modulus of the polymer and in terms of the reduced dynamic viscosity (η′—ηs)/(η—ηs), where η′ is the dynamic viscosity, ηs is the solvent viscosity, and η is the steady-flow solution viscosity. Results on the polystyrene—toluene system indicate that the system undergoes a change from Zimm-like to Rouse-like behavior with increasing concentration and, hence, with reduced frequency. No evidence of a reduced high-frequency limiting viscosity is observed and the value for the lowest concentration falls on a line extrapolated from earlier data of Lamb and Matheson. Results on the polystyrene DBP system indicate that the slope of logG′ vs log volume fraction of polymer increases at about 5% concentration, the predicted concentration for the onset of entanglement coupling. As concentration increases, a reduced high-frequency limiting viscosity is present up to the entanglement concentration, but beyond this point the reduced dynamic viscosity decreases and indicates a trend toward Rouse-like behavior at 20% concentration. Within experimental uncertainty neither solvent exhibits viscoelastic behavior.
One- and Two-Center Calculations on the Lowest-Lying Π States of HeH+
Authors: Hoyland James R.
Published: January 2005

Accurate two-center calculations using a basis set of elliptical orbitals are made on the lowest-lying singlet and triplet-Π states of HeH+. The calculated dissociation energies of these states are 0.234 eV for the singlet and 0.147 eV for the triplet. Single-center wavefunctions for these two states are also computed at the equilibrium internuclear separation predicted by the two-center results (8.05 bohrs for the singlet and 7.67 bohrs for the triplet). The differences in the energies of the one- and two-center calculations are 144 cal and 94 cal for the singlet and triplet, respectively. Expectation values of several operators are given along with calculated values of the spectroscopic constants.
Transfer of Electronic Energy between a Metastable Argon Atom and a Nitrogen Molecule
Authors: Fishburne E. Stokes
Published: January 2005

A detailed study has been made of the mechanism of electronic energy transfer between a metastable argon atom and a nitrogen molecule. The transition involves the excitation of nitrogen to the C3Π state. The metastable energy of argon is sufficient to excite the v′ = 2 level of the C3Π state if the nitrogen is originally in its v″ = 0 vibrational level of the X1Σ state. It was found that (1) the v′ = 3 level was not excited, (2) the population of the v′ = 0 level was greatly enhanced with the excess energy going into rotational energy of the N2 molecule, (3) the relative intensities of the v′ = 0, 1, and 2 levels could not be predicted on the basis of the Franck—Condon factors, and (4) the collision cross section for the observed energy transfer is about 100 times greater than the argon—argon de-excitation cross section. It is shown that the enhanced rotational structure of the v′ = 0 level of the C3Π state can be explained from the viewpoint of a minimum amount of initial internal energy transferring to relative kinetic energy of the particles. The v′ = 1 and 2 levels did not show enhanced rotational structure. From a consideration of the carbon monoxide—argon system, it is shown that the Wigner spin-conservation rule governs the efficiency of the electronic energy transfer during collision. This condition applies regardless of whether or not the transitions are optically allowed.
Reinvestigation of the Structures of Ethanol and Methanol at Room Temperature
Authors: Wertz D. L. , Kruh R. K.
Published: January 2005

Diffraction studies of ethanol and methanol indicate strong intermolecular hydrogen bonding between neighboring alcohol molecules at room temperature. Each oxygen has, on the average, two nearest oxygen neighbors at 2.7 Å in each alcohol. From an analysis of the radial-distribution function of each alcohol, a reasonable accounting of the observed intermolecular interactions is made.
Improved Design for the Trennschaukel: Measurement of the Thermal-Diffusion Factors in Gas Mixtures
Authors: Batabyal A. K. , Ghosh A. K. , Barua A. K.
Published: January 2005

A four-tube all-glass trennschaukel or swing separator, having several new features has been designed. Bulbs have been used at the hot and the cold ends of each tube to increase considerably the gas space in the isothermal regions. Thermocouples have been inserted into the top and the bottom end volumes to measure exact upper and lower temperatures. Two dummy tubes have also been placed on each side of the effective four-tube arrangement to eliminate dilution of the gas sample from the rocking arrangement. This apparatus has been successfully employed to measure thermal-diffusion factors of He–Ne, Ar–N2, and H2–CO2 mixtures over the temperature range from 275° to 390°K.
Electric-Field-Induced Spectral Shifts of the OH Vibrational Absorption Line in Alcohols
Authors: Handler Paul , Aspnes D. E.
Published: January 2005

It is shown that the electric-field-induced spectral shifts in the vibrational lines of polar molecules can be easily observed. Although the effect has been observed for many different alcohols, we report here only the data associated with 2,6 di-isopropyl phenol for its fundamental and overtone lines. It is also observed that the amount of association of the alcohols is affected by the electric field.
Noninvariance Groups in Molecular Quantum Mechanics. I
Authors: Wulfman Carl E. , Takahata Yuuzi
Published: January 2005

The problem of one electron moving in the field of many stationary nuclei is formulated in terms of the operations of the Lie algebras of E4, R5, and O4,1, all noninvariance groups of quantal electrostatics. This makes it possible to carry through and completely analyze one-electron molecular calculations using only concepts and operations of the theory of continuous groups. The approach is designed for the study of general laws of behavior of simple molecular systems. To exemplify it, it is used in its simplest form to uncover a suggestive approximate dynamical symmetry. This is related to a known angular momentum invariant that is instrumental in determining the properties of small molecules.
Gaussian Basis SCF Calculations for OH−, H2O, NH3, and CH4
Authors: Ritchie C. D. , King Harry F.
Published: January 2005

Extensive SCF LCAO MO calculations utilizing comparable Gaussian basis sets for OH−, H2O, NH3, and CH4 give SCF energies of −75.377, −76.034, −56.201, and −40.198 a.u., respectively. An ad hominem assumption of an error of 0.03 a.u. due to an incomplete basis set in each calculation leads to estimates of −75.41, −76.06, −56.23, and −40.23 a.u., respectively, for the Hartree—Fock limits, and of −0.39, −0.38, −0.33, and −0.28 a.u., respectively, for the correlation energies of these molecules. Details of the use of linear combinations of Gaussian functions as bases in molecular calculations are presented. The results show that considerable computation time can be saved with little sacrifice in accuracy for well-chosen combinations.
Isotropic Nuclear Resonance Shifts in Some Trigonal Co(II) and Ni(II) Chelate Systems
Authors: Jesson J. P.
Published: January 2005

Well-resolved high-resolution proton nuclear resonance spectra have been observed for solutions of Co(II) poly(1-pyrazolyl) borate chelate systems in CDCl3. In a previous paper [J. P. Jesson, J. Chem. Phys. 45, 1049 (1966)], optical and paramagnetic resonance data have been described for some of these compounds. The combined NMR, EPR, and optical data are treated for a variety of substituted complexes to give a quantitative evaluation of the dipolar contribution to the proton resonance shifts in the ligands. On this basis, an approximate separation of the dipolar and scalar contributions to the shifts is achieved. The scalar contributions are similar to those observed in the corresponding Ni(II) complexes. Some consideration is given to the nuclear relaxation times for the ligand protons in the Co(II) compounds. g-tensor components for the Co(II) complexes obtained from paramagnetic resonance measurements on magnetically dilute powers at 4.2°K are presented to demonstrate their insensitivity to the effects of ligand substitution.
Vibrational Spectra and Structure of Four-Membered Ring Molecules. III. Bromocyclobutane, Bromocyclobutane-d1, Bromocyclobutane-d4, and Bromocyclobutane-d5
Authors: Durig James R. , Green William H.
Published: January 2005

The infrared spectra of bromocyclobutane, α-bromocyclobutane-d1, β,β,β′,β′-bromocyclobutane-d4, and α,β,β,β′,β′-bromocyclobutane-d5 in both the liquid and vapor phases have been recorded from 4000 to 250 cm−1. The far-infrared spectra of bromocyclobutane and β,β,β′,β′-bromocyclobutane-d4 have been recorded to 33 cm−1. The Raman spectra of the four isotopic species of bromocyclobutane in the liquid state have also been recorded and depolarization values have been measured; the carbon—bromine stretching region of bromocyclobutane-d1 has been scanned at temperatures varying from 35° to −83°C. The spectra have been interpreted by considering the molecules as having one plane of symmetry and belonging to point group Cs. Frequency assignments which are based on group-frequency correlations, isotopic shifts, depolarization values, band contours, and relative intensities where applicable are given for the normal vibrations. The assignments are tabulated and discussed according to symmetry species. The regimens of the product and noncrossing rules have been followed. Support for the existence of ``equatorial'' and ``planar'' conformers is presented and the nature of the potential function governing the ring-puckering vibration for bromocyclobutane is discussed.
Argon—Fluorine Phase Diagram
Authors: Barrett C. S. , Meyer L. , Wasserman J.
Published: January 2005

The phase diagram of solid argon and solid fluorine was determined by x-ray diffraction and the solidus and liquidus by thermal analysis. Although the high-temperature structures of oxygen and fluorine are very similar, their phase diagrams with argon are quite different. The addition of F2 does not change the fcc Ar structure to hcp as the addition of O2 does. In the solid, the miscibility gaps between the Ar-rich and the F2-rich solid solutions extend as two-phase regions from 25%±2% to 97%±2% F2 in the low-temperature (α) range at the eutectoid temperature (41°K). The presence of 22% F2 slightly contracts the fcc Ar lattice; the lattice constant at that concentration and 23°K is 5.295±0.010 Å compared with the Ar lattice constant, 5.318 Å. The solidus line is horizontal at 53°K from 37%±2% to 95%±2% F2, and there is a eutectic at 72%±2% F2; up to that concentration, the solidus and liquidus are widely separated. The β—α F2 transformation was observed visually; the β phase is soft and transparent, the α phase is pale yellow, opaque, very hard, and brittle. The transformation is frequently accompanied by a sharp click and an explosion blowing out the window of the sample holder.
Spectral Contours of Continuous Absorption Bands of Complex Molecules
Authors: Voorhof H. , Pollak H.
Published: January 2005

An analytical expression for the description of the shape of continuous absorption bands is calculated within the framework of a new one-dimensional potential model. The calculations are based on a semi-classical approximation of the Franck—Condon factors and on the application of the Mehler formula for the sum calculation of statistically weighted position probability densities.
Proton Magnetic Resonance of Dimethyl Phthalates
Authors: Schug John C. , Smith Barbara P.
Published: January 2005

We have studied the high-resolution proton magnetic resonance spectra of the ring protons in dimethyl phthalate, dimethyl isophthalate, and dimethyl terephthalate. The proton chemical shifts were determined relative to benzene in a series of solvents of widely varying dielectric constant, with both species at infinite dilution. This effectively removes the solvent van der Waals contribution to the observed shifts, and the remaining shifts are in accord with Buckingham's theory of dielectric reaction fields. Extrapolation to a medium of unit dielectric constant was performed in order to obtain chemical shifts typical of isolated molecules. These values were then approximately corrected for intramolecular electric and magnetic fields. For the two nearly planar molecules, the corrected values were correlated with pi-electronic charge densities obtained by Hückel molecular-orbital calculations. The failure of this correlation in the case of dimethyl phthalate can be attributed to the large deviations from planarity due to extreme steric hindrance.
Tetracene Dimer
Authors: Katul J. A. , Zahlan A. B.
Published: January 2005

It is shown that tetracene dimerizes. The association equilibrium constant K=2.2×10−4 exp(7.2/RT) for 283°≥T≥168°K. The absorption and emission spectra of the dimer are compared with those of the monomer and of crystalline tetracene. The dimer and the crystal spectra are similar.
Interaction Potential of the Inert Gases
Authors: Klein M. L. , Munn R. J.
Published: January 2005

The best available pair potentials of Ne, Ar, Kr, and Xe derived from second virial coefficient and low-pressure gas transport data are used to calculate the lattice parameter, sublimation energy, and bulk modulus for the solids at 0°K. If pairwise additivity is assumed for the interatomic forces in the solid, the agreement with experiment is poor. Inclusion of the Axilrod—Teller triple-dipole force improves the agreement with experiment but discrepancies still remain. Possible reasons for these discrepancies are discussed.
Matrix Elements of Spin-Interaction Operators
Authors: Harris Frank E.
Published: January 2005

Methods are given for calculating matrix elements of an arbitrary two-electron spin-dependent operator, using wavefunctions based on open-shell spin-projected spin—orbital products. The formalism is developed both in terms of the entire spin space of the desired multiplicity and in terms of the projection operators discussed by Löwdin. The results are also specialized to the important case of orthogonal spatial orbitals. The methods are illustrated by application to the Fermi-contact interaction.
Kinetics and Mechanism of the Photochemical Valence Tautomerization of Hexafluorobenzene
Authors: Haller Ivan
Published: January 2005

The kinetics of the photoisomerization of hexafluorobenzene to its ``Dewar'' isomer has been investigated in the gas phase at 2652, 2482, 2288, and 2120 Å. The addition of gases capable of removing vibrational excitation enhances the quantum yield of isomerization indicating that the vibrationally ``hot'' isomer is formed in a rapid reaction. The intrinsic quantum yields of the isomerization process, obtained by extrapolating the observed yields to infinite pressure, are 0.0207±0.0013, 0.0463±0.0031, and 0.081±0.014 at 2652, 2482, and 2288 Å, respectively. These results are in qualitative agreement with predictions of the correlation between the symmetry of the excited state and the direction of photochemical isomerization.
On the Stochastic Theory of Dissociation and Recombination of Diatomic Molecules in Inert Diluents
Authors: Brau Charles A.
Published: January 2005

A formal stochastic theory is developed to describe the dissociation and recombination of diatomic molecules by inert third bodies, and the manner in which this reaction is coupled with internal relaxation processes. Singular perturbation methods are used to obtain a uniformly valid asymptotic solution to the nonlinear master equation in the limit when the internal relaxation times are short compared with the dissociation time. The solution shows that the reaction begins with a short transient during which the internal distribution function relaxes from the initial state to a ``quasisteady'' state. Following this, the reaction obeys the usual phenomenological equations with well-defined rate coefficients. It is shown that to lowest order the observed rate coefficients are constants during the quasisteady period, and retain their nonequilibrium values as the reaction approaches equilibrium. In higher orders the dissociation and recombination rate coefficients depend on the instantaneous composition of the gas. However, the ratio of the instantaneous values of the dissociation and recombination rate coefficients remains equal to the equilibrium constant. It is also shown that the initial transient causes an observable ``incubation time'' to appear in the reaction. The formula for the incubation time is derived, and applied to the special cases of dissociation behind a shock wave and recombination following flash photolysis.

The results are applied to the dissociation and recombination of diatomic molecules possessing rotational, vibrational, and electronic degrees of freedom.
Electrostatic Hellmann—Feynman Theorem Applied to the Long-Range Interaction of Two Hydrogen Atoms
Authors: Hirschfelder Joseph O. , Eliason Morton A.
Published: January 2005

The electrostatic Hellmann—Feynman theorem is used to calculate exactly the leading term in the 1/R expansion of the force of interaction between two well-separated hydrogen atoms, −6 C6/R7. The exact wavefunction can be expanded in the series ∑ n=0∞ψnR−n.The expectation value of the approximate wavefunction ψ0+ψ3 gives the exact value of C6/R6. However, with the use of the electrostatic Hellmann—Feynman theorem it is necessary to know ψ0, ψ3, ψ4, and that part of ψ7 which has the same angular dependence as the electron coordinate za1 in order to determine −6C6/R7. Only 7% is contributed by ψ3 and ψ4; the other 93% is due to the ψ7. The relevant part of ψ7 is determined as the solution to a mixed second-order perturbation equation (first order with respect to each of two perturbations).
SCF—MO—LCAO—CI Treatment of the Pi-Electronic Structure of Formaldehyde Using Ohno's Formula for βCO and Constrained to Satisfy Koopmans' Theorem Exactly
Authors: Pilar F. L.
Published: January 2005

The Pople—Pariser—Parr simplification of Roothaan's matrix formulation of the Hartree—Fock self-consistent-field (SCF) equations is applied to the pi-electronic portion of the formaldehyde molecule as (1) a test of the use of Ohno's resonance integral formula as a basis for obtaining self-consistent resonance integrals for heterobonds and (2) as a test of the effect of constraining the energy of the highest occupied orbital to satisfy Koopman's theorem exactly. The calculated spectroscopic intervals, dipole moments, and charge distributions are not too far different from those obtained by the self-consistent-electronegativity method of Brown and Heffernan, but there are indications that the present method may form a more satisfactory basis for extension to other heteroatomic conjugated systems.
Internal Rotation Barriers for Hydrazine and Hydroxylamine from Ab Initio LCAO—MO—SCF Wavefunctions
Authors: Fink William H. , Pan Dorothy C. , Allen Leland C.
Published: January 2005

LCAO—MO—SCF ab initio wavefunctions with atomic basis orbitals of double-zeta accuracy have been constructed for N2H4 and NH2OH and the potential-energy curves versus internal-rotation angle have been determined. Similar wavefunctions for CH3CH3, CH3OH, CH3NH2, and H2O2, reported previously, showed a quantitatively useful correlation with experimental barrier heights and shapes. Since experimental information on the N2H4 and NH2OH barriers is incomplete or unknown, the theoretical results presented here may help guide experimental work. Decomposition of the total energy into one- and two-electron components has been found previously to help elucidate the physical origin of the rotational barrier, and results for the species studied here are given. The wavefunctions presented here (and those reported previously for the species noted above) are the most accurate available for molecules possessing a rotational barrier about a single bond, and comparison is made with the results of the other existing ab initio wavefunctions.
NMR Studies of Inorganic Fluorides. III. Si3F8
Authors: Johannesen Rolf B.
Published: January 2005

A high-resolution NMR study of octafluorotrisilane, Si3F8, is reported. The chemical shifts of 19F and 29Si, relative to SiF4 as a reference, are given. Coupling constants, including in every case the relative sign, are given for isotopic species containing not more than one 29Si atom. The results are compared with the corresponding values for SiF4 and Si2F6.
Effective Field Parameters in Iron Mössbauer Spectroscopy
Authors: Hoy Gilbert R. , Chandra Subhas
Published: January 2005

Relatively simple computational methods for interpreting Mössbauer spectra, in which there are simultaneously static quadrupole and hyperfine interactions, have been developed. Our explicit calculations are restricted to the case when either the source or absorber is a ``single line'' and the nuclear levels are the same as in the 57Fe 14.4-keV transition. Experimental spectra for powdered RbFeF3 and FeCr2S4 have been obtained and are analyzed using these methods. Our results show that although the quadrupole interaction ΔEQ is zero above the transition temperatures of both RbFeF3 and FeCr2S4 it is rather large below, i.e., in FeCr2S4, ΔEQ=0.78 mm/sec at 77° K and in RbFeF3, ΔEQ=3.00 mm/sec at 4°K. The isomer shift, the effective internal magnetic field, and its orientation with respect to the principal axes of the electric-field-gradient tensor in these substances at various temperatures are also obtained.
Molecular Beam Kinetics: Reactions of K, Rb, and Cs with Br2 and I2
Authors: Birely J. H. , Herm R. R. , Wilson K. R. , Herschbach D. R.
Published: January 2005

Crossed-beam studies have been made of the reactions of K, Rb, and Cs atoms with Br2 and of K and Cs with I2. It is found that for all these systems: (1) The reaction cross sections are remarkably large, ≳150 Å2. (2) Most of the alkali halide product recoils into the forward hemisphere with respect to the incident alkali atom beam, with scattering angle θ≲60° (in the center-of-mass system). However, there also appears to be considerable intensity (∼20% of the forward peak) throughout the backward hemisphere, 90°<θ<180°. (3) The angular distribution (in the c.m. system) of alkali atoms scattered without reaction falls off much more rapidly at wide angles than for collisions between unreactive molecules of comparable size. (4) The shape of the angular distributions of both the reactive and nonreactive scattering is the same for various alkali metals, but differs appreciably for Br2 and I2. (5) Most of the chemical energy released appears as internal excitation of the products. This could include substantial rotational and/or electronic excitation, but other evidence shows that vibrational excitation of the newly formed bond is dominant. All these properties can be accounted for by a model (suggested originally by Polanyi and Magee) which assumes that the attacking alkali atom transfers its valence electron to the halogen at large distances (≳7 Å), so that these are in effect ion-recombination reactions.
Fermi Doublet ν1, 2ν2 in the Cyanate Ion
Authors: Decius J. C. , Gordon D. J.
Published: January 2005

Cyanate ion enriched in 13C, 15N, or 18O has been introduced into single crystals of KBr and KCl grown from the melt. The infrared absorption of such matrix-isolated molecular ions has been observed between 1150 and 1350 cm−1 from room temperature down to liquid-N2 temperature. On the basis both of isotopic frequency shifts and changes in the relative intensities, an earlier assignment of ν1 and 2ν2 is reversed; the new assignment parallels the situation recently brought to light for carbon dioxide.
Atomic Screening Constants from SCF Functions. II. Atoms with 37 to 86 Electrons
Authors: Clementi E. , Raimondi D. L. , Reinhardt W. P.
Published: January 2005

Minimal basis-set atomic functions for the ground-state atoms from Rb(Z=37) to Rn(Z=86) are presented. These functions are analyzed in order to obtain systematic data for the screening constants and atomic radii following the work initiated by Slater.
Microwave Spectrum, Structure, and Quadrupole Interaction of Trifluoro-iodo Silane
Authors: Sams Lewis C. , Jache Albert W.
Published: January 2005

Rotational spectra of trifluoro-iodo silane observed with a video microwave spectrometer were fitted to the following molecular constants: B=1118.84 Mc/sec, eqQ estimated to be −1450 Mc/sec. Since dSiF and φFSiF have been found in other molecules to be 1.560±0.005 Å and 108°30′±1° these parameters were assumed, and dSiI was found to be 2.387±0.02 Å. This observed Si–I bond shortening has been found in other molecules and is attributed to ionic and double-bond character.