bluuebunny/crossref_metadata_2025 huggingface dataset:
Paramagnetic-Resonance Studies of Irradiated High-Density Polyethylene. II. Effect of Irradiation Dose on the Radical Species Trapped at Room Temperature
Authors: Lawton Elliott J. , Balwit J. S. , Powell R. S.
Published: January 2005

The previous paper presented a study of the radical species in irradiated Marlex-50 at low dose levels. This paper extends that study to a level of 4000 megaroentgens. The kind and relative number of each radical trapped at room temperature (RT) depends on the degree and tightness of the crystalline and crosslinked fractions during irradiation. At least two of three distinct species, having different hyperfine structures (six-, five-, and a single-line) are present in varying concentrations at all doses. The six- and five-line radicals are trapped in the crystal, whereas the single-line radical is trapped in the highly crosslinked medium. During irradiation at RT and liquid-nitrogen (LN) temperature, the crystal is not as effective in trapping the six-line radical as in the absence of irradiation. At 640 megaroentgens the six-line radical does not survive during irradiation at RT, leaving the five- and single-line radicals above this level. The single-line radical appears at 320 megaroentgens and increases until at 3000 megaroentgens, where crystallinity is zero, it accounts for about 70% of the total.

Heating the irradiated samples causes all radicals to disappear; the ``extinction temperatures'' for the six-, five-, and single-line radicals were 90°, 135°, and about 250°C, respectively. The relative effectiveness of the preirradiated annealed samples compared to the nonirradiated Marlex-50 in trapping radicals at RT was 0.5 for the 20-megaroentgen, 1.0 for the 320-megaroentgen, and 1.4 for the 4000-megaroentgen preirradiated material. There is evidence in the uv spectrum for conjugated double bonds in the highly irradiated samples. It is proposed that the single-line radical is initially formed adjacent to the conjugated sequence and then becomes trapped within the sequence by resonance. The radical could be represented as –CH=CH–CH=CH–CH– lim ←·→CH=CH–CH=CH–..
Structure of the Infrared Y Bands of N2
Authors: Dieke G. H. , Heath D. F.
Published: January 2005

The rotational analysis of the n+4, 3 band of the ``Y'' system of N2 shows that the initial state is a 3Σu— level with Bn+4 = 1.3325. The band has exactly the structure to be expected from a 3Σu—→3IIg transition and all expected 27 branches have been observed. The triplet separation of the 3Σ state degenerates into a doublet for all but the lowest values of K as the two states with J = K±1 nearly coincide.
Search for a Jahn-Teller Effect in IrF6
Authors: Claassen Howard H. , Weinstock Bernard
Published: January 2005

An investigation of the vibrational spectra of IrF6 has failed to reveal the anomalies found for OsF6 that were attributed to a Jahn-Teller coupling. This is taken to indicate that the Γ8 ground electronic state of IrF6 has a strong spin character. For the vapor in the NaCl range the observed absorption frequencies (cm—1) and their assignments were: 720 (σ3), 852 (σ2+σ6), 921 (σ2+σ4), 979 (σ1+σ4), 1364 (σ2+σ3), and 1425 (σ1+σ3). A Raman shift of 651 cm—1 ascribed to σ2 was obtained for a solution of IrF6 in n-C7F16.
Transferability of Urey-Bradley Force Constants. IV. Methyl Halides
Authors: Overend John , Scherer James R.
Published: January 2005

Urey-Bradley force constants have been fitted by least squares to the vibrational frequencies of CH3F, CH3Cl, CH3Br, CH3I, and their fully deuterated isotopes. Both observed and zeroth-order frequency data have been used and the corresponding sets of force constants have been compared.
Energy of Interaction of Two Helium Atoms
Authors: Moore Neal
Published: January 2005

The interaction energy of two helium atoms in the ground state is calculated as a function of internuclear separation. Use is made of a variational trial state function developed in analogy with Hirschfelder and Linnett's treatment of the hydrogen-hydrogen interaction. The results are in good agreement with the best previous treatments in the repulsive region as well as with the results of Rosen, Margenau, and Page in the neighborhood of the van der Waals minimum; in addition, information is obtained concerning the instantaneous mutual polarization of the two atoms.
Interaction Energies for the H–H2 and H2–H2 System
Authors: Vanderslice Joseph T. , Mason Edward A.
Published: January 2005

Interaction energies for the H–H2 and H2–H2 systems have been obtained by a semiempirical perfectpairing procedure used previously. The results have been compared with interaction energies obtained from other sources and the agreement among the different curves is reasonably good. A brief discussion of the previous applications of this semiempirical scheme to other systems is included.
Dissolution Kinetics at Dislocation Etch Pits in Single Crystals of Lithium Fluoride
Authors: Ives M. B. , Hirth J. P.
Published: January 2005

The kinetics of dissolution at dislocation etch pits on lithium fluoride in dilute aqueous solutions of ferric fluoride were studied by interferometric observations on etched surfaces.

The effects on dissolution of the variables time, temperature, undersaturation, crystal perfection, and crystal orientation were determined. It was found that dissolution was consistent with the mechanistic theories of crystal dissolution involving dissociation of lithium fluoride from monomolecular ledges on close-packed surfaces and subsequent diffusion into solution, if a time-dependent adsorption of inhibitor at the receding ledges is invoked.
Heterogeneous Reactions Studied by Mass Spectrometry. II. Reaction of Li2O(s) with H2O(g)
Authors: Berkowitz Joseph , Meschi David J. , Chupka William A.
Published: January 2005

The reaction of water vapor with lithium oxide was studied by a mass-spectrometric technique. In the temperature range 1100–1400°K and with water vapor pressures of the order of 0.1 mm, the major reaction product in the vapor phase was LiOH. Smaller amounts of Li2(OH)2 and traces of Li3(OH)3 were measured. Various equilibria among the above species were studied with the use of isotopic substitution for lithium and hydrogen. The decomposition of lithium hydroxide was studied in the temperature range 500–600°K. Structural parameters and vibrational frequencies were estimated and thermodynamic functions were calculated for the LiOH and Li2(OH)2 molecules. The following heats of reaction, which are consistent within experimental error, were then determined: Li2O(s)+H2O(g)→2LiOH(g)ΔH1300∘=79.0±2.0 kcalLi2O(s)+H2O(g)→Li2(OH)2(g)ΔH1250∘=15.0±2.0 kcalLi2(OH)2(g)→2LiOH(g)ΔH1300∘=60.0±3.0 kcal2LiOH(s)→Li2O(s)+H2O(g)ΔH500∘=30.4±1.0 kcal2LiOH(s)→Li2(OH)2(g)ΔH600∘=45.0±3.0 kcal.
Secondary Reactions in a Gas Discharge
Authors: Ortenburger Irene B. , Hertzberg Martin , Ogg Richard A.
Published: January 2005

The pressure variations of H+, H2+, H3+, He+, and HeH+ ions emanating from an electrodeless discharge in pure hydrogen and in mixtures of hydrogen and helium have been measured. Mass analysis was accomplished with a ``strong-focusing'' mass spectrometer. The analysis of the results in hydrogen are discussed, as well as the alternative mechanisms for hydrogen dissociation. From the results in hydrogen-helium mixtures, a value of 0.37±0.15 has been obtained for the ratio k2′/k1′; where k2′ is the rate constant for reaction He++H2→HeH++Hand k1′ is the rate constant for the reaction H2++H2→H3++H.In addition, a value of 0.016±0.013 has been obtained for the ratio k3′/k2′, where k3′ is the rate constant for the reaction H2++He→HeH++H.
Proton-Magnetic-Resonance Study of Barium Bromide Monohydrate
Authors: McGrath J. W. , Silvidi A. A.
Published: January 2005

The proton-magnetic-resonance doublets were obtained for rotation of the crystal around its c axis. From these data, the proton-proton separation was computed to be 1.56±0.02 A. The hydrated water molecule was found to lie in one orientation whose proton-proton axis makes direction angles of α0=89±1°, β0=1±1°, and γ0=90±6°, measured from the positive a, b, and c crystallographic axes, respectively. This orientation fits well into the crystal structure and indicates that the complex, BrI— —H–O–H— —BrII, exists.

Line widths range from 6.5 to 4.2 gauss and show a correlation with T1 as a function of orientation. Observation was necessarily made with some saturation.

A new effect, an asymmetry of line areas in the doublets, was observed for narrow ranges near two crystal orientations. The two orientations were symmetrically close to that for which the proton-proton line was parallel to the external magnetic field. It may be due to crossing of the barium quadrupole resonance frequencies over the magnetic-resonance frequencies of the protons.
Charge Transfer Reactions Producing Intrinsic Chemical Change: Methyl, Methylene, and Hydrogen Radicals Produced from Argon and Methane Reactions
Authors: Melton C. E.
Published: January 2005

Charge transfer reactions producing intrinsic chemical changes in the neutral molecule have been proven by mass spectrometric techniques. The charge transfer reaction Ar++CH4→Ar+CH3++Hproducing an intrinsic chemical change in CH4 was found to be more probable by a factor of five than the simple charge transfer reaction Ar++CH4→Ar+CH4+.Charge transfer reactions in mixtures of Ar and CH4 and Kr+CH4 were studied over the pressure range of 0.1–0.5 mm of Hg in the ionization chamber. Reactions were elucidated by catalytic and negative ion studies as well as by the usual pressure and appearance potential techniques. In the Kr+CH4 mixture, the reaction Kr++CH4→Kr+CH3++Hproducing the charged radical CH3+ was found to have a high probability. Absolute values for rate constants and cross sections are given for all of the charge transfer reactions observed in the Ar+CH4 mixture. Products from these elementary charge transfer reactions are correlated to previously reported radiolytic, α ionization (W value), and hydride ion transfer studies.
Spin Exchange in Biradicals
Authors: Reitz D. C. , Weissman S. I.
Published: January 2005

The electron spin resonance spectra of four isotopically labeled biradicals have been observed. The hyperfine splittings demonstrate independence of the halves.
Spin Densities in Organic Free Radicals
Authors: Brown Thomas H. , Anderson D. H. , Gutowsky H. S.
Published: January 2005

The proton hyperfine constants obtained from proton magnetic resonance spectra of polycrystalline free radicals and from valence bond calculations of π-orbital spin densities are compared for the free radicals α,α′-diphenyl-β-picryl hydrazyl, and tris-p-chlorophenylaminium perchlorate. Two lines are observed in the proton magnetic resonance spectra, one shifted upfield and one downfield from the normal resonance frequency. These are assigned to the ortho and para protons, and the meta protons of the free radicals, respectively. Though the agreement between theory and experiment is not quantitative for the hyperfine constants, the theoretical and experimental ratios of hyperfine constants agree within experimental error. This serves to verify the existence of positive and negative spin densities and the signs of some of the relationships involved.
On the Equilibrium C–H Distance in Methane
Authors: Stevenson D. P. , Ibers James A.
Published: January 2005

An equilibrium C–H distance re of 1.091±0.002 A has been calculated with the aid of a normal coordinate treatment from vibrational and rotational spectroscopic data on CH4 and CD4. From these results we also derive for the mean C–H distance, of interest in electron diffraction studies, the value 1.102±0.002 A.
Green and Purple Sulfur: Electron-Spin Resonance Studies
Authors: Radford H. E. , Rice F. O.
Published: January 2005

Electron spin resonance absorption has been found in the colored deposits formed by condensing heated sulfur vapor on cold surfaces. Complexities in the resonance spectrum give evidence for the existence in the cold deposits of at least two types of trapped sulfur radicals with differing degrees of internal magnetic anisotropy. Measurements of the intensity and stability of the resonance absorption yield information on the radical trapping process.
Nuclear Magnetic Resonance in Solid Adamantane
Authors: McCall David W. , Douglass Dean C.
Published: January 2005

Proton magnetic resonance studies of solid adamantane reveal the existence of a rotational transition at about —130°C. The activation energy associated with the rotational transition is found to be about 5 kcal/mole. Theoretical and experimental second moments agree if it is assumed that the molecules are rigidly fixed below the transition and rotate freely above the transition.
Separation Theorem for Degenerate Eigenvalues
Authors: Davies D. W.
Published: January 2005

An algebraic theorem concerning the separation of the eigenvalues of a matrix is discussed for degenerate eigenvalues in variation calculations. It is shown that the occurrence of degenerate eigenvalues in a given approximation does not prevent the application of the theorem to the determination of upper bounds for exact eigenvalues in physical problems.
Threshold Law for the Probability of Excitation of Molecules by Photon Impact. A Study of the Photoionization Efficiencies of Br2, I2, HI, and CH3I
Authors: Morrison J. D. , Hurzeler H. , Inghram Mark G. , Stanton H. E.
Published: January 2005

A study is made of two types of excitation process in molecules, leading to either dissociation to an ion-pair, or to autoionization. The latter process, in the case of the iodine-containing molecules, clearly makes a very significant contribution to the total ionization. The threshold law for the probability of excitation by photon impact is shown to be approximated closely by a delta function of the excess energy. Energy values are measured for various states of the molecules, and are in good agreement with available spectroscopic data. The electron affinities of Br and I are found to be 3.53±0.12 and 3.13±0.12 ev, respectively.
Electron-Spin Resonance of Electrochemically Generated Free Radicals. Isomeric Dinitrobenzene Mononegative Ions
Authors: Maki August H. , Geske David H.
Published: January 2005

The mononegative ions of meta-, ortho- and para-dinitrobenzene have been prepared in acetonitrile by controlled potential electrolysis within a microwave cavity and their electron spin resonance observed. The radical spectra exhibit hyperfine structure due to the isotropic magnetic interaction of the unpaired electron with the nitrogen and ring proton nuclear moments. Coupling constants were obtained with the aid of deuterium substitutions in the parent molecule. The nitrogen hyperfine coupling constants for the isomeric meta, ortho, and para anions were found to be 4.68, 3.22, and 1.74 gauss, respectively, and were identical for each of the two nitrogen nuclei of a given radical. Proton coupling constants range between 0.42 gauss and 4.19 gauss. The larger total hyperfine width of the meta-dinitrobenzene anion compared with the ortho and para isomers is ascribed to the existence of negative spin density in the π system of the first-mentioned radical and to the possibility of quinonoid resonance in the others which places considerable unpaired spin density in the oxygen nonbonding orbitals.
Diamagnetism as a Test of Wave Functions for Some Simple Molecules
Authors: Banyard K. E.
Published: January 2005

A theoretical study is made of the diamagnetism of some simple molecules in a gaseous form, attention being mainly devoted to the ``neon-like'' series Ne, H2O, NH3, and CH4. In this way an attempt is made to gain insight into the way in which the radial electron density distribution within the molecules is influenced, firstly, by the allowance of exchange effects and secondly, by the inclusion of angular terms which must be accounted for in any ``physically real'' description of the electron density.

In general, it is found that exchange effects cause the radial density distribution to contract, while the inclusion of angular terms results in the subsequent radial electron density becoming more diffuse.
Mass Spectra of Aluminum(III) Halides and the Heats of Dissociation of Al2F6(g) and LiF·AlF3(g)
Authors: Porter Richard F. , Zeller Ernest E.
Published: January 2005

Mass spectra of gaseous aluminum(III) chloride and bromide have been obtained and interpreted quanitatively in terms of the degree of association in the vapor phase. Ion currents indicative of a molecular trimer of AlCl3 have been observed. Mass spectra of the vapors effusing from a Knudsen cell containing AlF3 have been obtained and the stability of the molecular dimer of AlF3(g) has been determined quantitatively. Mass spectra of vapors from LiF–AlF3 mixtures indicate the existence of a stable LiF·AlF3(g) molecule. Ion current data have been obtained as a function of condensed phase composition. A second complex molecular species which appears to be either (LiF)2·AlF3(g) or (LiF·AlF3)2(g) has been observed. For the reaction Al2F6(g)=2AlF3(g), ΔH°1000=48.0±4.0 kcal/mole dimer, and for LiF·AlF3(g)=LiF(g)+AlF3(g), ΔH°1000=73±4 kcal/mole.
Effects of Pressure on Proton Spin-Lattice Relaxation in Several Degassed Organic Liquids
Authors: Nolle A. W. , Mahendroo P. P.
Published: January 2005

The hydrogen nuclear magnetic relaxation time (T1) for degassed samples of several organic liquids has been measured, by a transient method, at pressures up to 1400 kg/cm2, primarily for comparison with results obtained without degassing. Certain of the liquids were investigated, without degassing, by Benedek and Purcell, who concluded that T1 decreases under pressure less rapidly than the rates of translational processes (fluidity and diffusion). The present results confirm this for degassed methyl iodide and n-heptane, in both of which the effect of degassing is to increase T1 less than 20%. For benzene and toluene, degassing causes T1 to increase by several hundred percent, and the preceding conclusion ceases to apply, but instead, in the degassed samples, the relative rate of decrease of T1 under pressure is comparable to that of the fluidity; in benzene, at low pressures, it is greater. Additional pressure studies are reported for purified cyclohexane, for purified 1,1,1-trichloroethane, and for chloroform, which was not successfully purified.
Electronic Structure and Hyperfine Structure Constants of NO Molecule
Authors: Lin Chun C. , Hijikata Katsunori , Sakamoto Michiko
Published: January 2005

The coupling constants of the magnetic hyperfine, electric quadrupole, and spin-orbit interaction have been calculated from the self-consistent field molecular orbitals formed by linear combination of atomic orbitals. The calculated values of the electron spin-orbit, nuclear spin-orbit, and nuclear-electronic spin-spin interaction constants agree reasonably well with experiment. The results for the nuclear quadrupole coupling constant and the Fermi contact term are less satisfactory, although the latter can be improved by configuration mixing. The relations of these coupling parameters to the electronic structure of the molecule are discussed.
Identification of Colloidal Sodium in Sodium Azide
Authors: Miller Brian S.
Published: January 2005

Under treatment with ultraviolet radiation and heat, sodium azide develops an optical absorption band centered at 520 mμ. The centers responsible for this band have been identified by the dual techniques of electron spin resonance and cryoabsorption spectroscopy as colloidal sodium.
Spectral Solvent Shift. I. Paraffin Hydrocarbon Solvent Interactions with Polynuclear Aromatic Hydrocarbons
Authors: Weigang O. E.
Published: January 2005

The electronic shifts for 11 ultraviolet transitions of the chromophores naphthalene, phenanthrene and the polar aromatic hydrocarbon, azulene, have been observed in a series of 17 paraffin hydrocarbon solvents from isopentane to n-tridecane. The contribution to the shift of branching and cyclization of solvent molecules has been observed by including the five structural isomers of hexane, 2,2,4-trimethylpentane and 2,2,5-trimethylhexane together with the cyclo- and methylcyclopentanes and hexanes.

The statistical approach is used to interpret the electronic shifts in terms of interbond potentials and the solvent radial distribution function and is compared to the McRae extension of the Bayliss solvent shift theory. Dispersive type potentials suffice to account for the frequency shifts of transitions, except the 1Lb transition of azulene which shifts to the blue from the vapor to hydrocarbon solutions. The behavior can be accounted for by a change in the static dipole moment of azulene on excitation, a phenomenon predicted by quantum mechanical calculations on the molecule.
Interatomic Distances in FeS2, CoS2, and NiS2
Authors: Elliott Norman
Published: January 2005

The crystal structures of FeS2, CoS2, and NiS2 have been re-examined. The sulfur-sulfur distances are found to vary, depending on the number of antibonding electrons shared with the metal ions.
Thickness of Shock Fronts in Argon
Authors: Hansen K. , Hornig D. F.
Published: January 2005

The accuracy and sensitivity of the optical reflectivity method for determining the thickness of shock fronts have been improved. The thicknesses of shock fronts in argon have been measured up to M=2.38. Most of the effort was concentrated at M=2.38 where the reciprocal thickness in mean free paths, l0/L0=0.234±0.007. At M=2.38 the front is about twenty percent thicker than calculated from the Navier-Stokes equations but the thickness agrees very closely with that calculated by Muckenfuss using a bimodal distribution function.
Kinetic Theory of the Moderately Dense Rigid-Sphere Fluid. V. Relaxation in Momentum Space
Authors: Harris Robert A. , Rice Stuart A.
Published: January 2005

We consider the problem of a dense rigid-sphere fluid at equilibrium in configuration space but perturbed in momentum space. The relaxation time for the return to equilibrium is computed analytically and shown to correspond to very few collisions—about four at gas densities and about one at liquid densities. This result is in good agreement with machine computations by Alder and Wainwright and shock-tube measurements by Greene, Cowan, and Hornig. The results indicated that correlated successive binary collisions need not be considered to first order in the finite dense rigid-sphere fluid.
Temperature Dependence of the Rates of Addition of Oxygen Atoms to Olefins
Authors: Cvetanović R. J.
Published: January 2005

Relative rates of addition of oxygen atoms to several representative olefins have been measured at 25° and 125°C, and the ratios of the pre-exponential factors and differences in activation energies have been calculated from the mean values of the relative rate constants at the two temperatures. The results obtained show that the differences in reactivities are primarily due to differences in the activation energies while the pre-exponential factors remain approximately constant.
Growth Poisoning of Lithium Fluoride from Aqueous Solutions
Authors: Sears Gerald W.
Published: January 2005

The presence of a few ppm of step poisons strongly alters both crystal growth and dissolution rates. It was known that a few ppm ferric fluoride was a poison for the dissolution of lithium fluoride. In the present report it is shown that ferric fluoride is also a growth poison for lithium fluoride from aqueous solution. Ferric fluoride has the properties characterizing a step poison for the lithium fluoride-water system.
Preliminary Analysis of U4+ Ion Spectra in Crystals
Authors: Satten Robert A. , Young Donald , Gruen Dieter M.
Published: January 2005

An analysis of a number of features of the absorption spectra of U4+ ions in crystals is given. Absorption spectra of crystals of the compounds Cs2UCl6, and [N(CH3)4]2 UCl6, and to a lesser extent [N(C2H5)4]2 UCl6 have been studied at room temperature, liquid N2 and liquid He temperatures. The visible spectrum is essentially entirely vibronic. Pure electronic transitions are absent or very weak in thick crystals in agreement with a model of electric dipole transitions within the 5 f2 shell at an equilibrium site of inversion symmetry. We believe this to be the first demonstrated case of an essentially purely vibronic spectrum reported for rare earth or actinide salts. The three ``ungerade'' frequencies of the UCl6= complex are coupled to the electronic frequencies and are determined by their appearance with the same frequency of superposition in all three salts as well as by being the most intense of the vibronic lines in every group in which they appear. Other lattice modes and internal frequencies of the tetramethylammonium ion are also found to be superimposed. The weak pure electronic transitions are fairly sharp, an indication that there is still considerable shielding in the 5 fn electronic states even though this shielding is less than in 4 fn states. The independence of superimposed vibration frequencies on 5 f2 electronic states indicates the fact that the 5 f states do not contribute much to the binding. The similarity in the spectra of the three salts studied is due to the fact that the nearest-neighbor Cl— ions are the principal origin of the crystalline field in contrast to the rare earths, wherein this type of similarity is due to the fact that the crystalline field is small and each group of lines represents a multiplet level of the free ion. Evidence is presented that the crystalline field splitting is larger than hitherto believed and is the same order of magnitude as the spin-orbit interaction. Methods of attacking the problem of the experimental classification and calculation of energy levels in the situation in which three major interaction are of comparable size are discussed.
Vibrational Spectra of Penta-Deutero-Fluoro-Benzene
Authors: Steele D. , Lippincott E. R. , Xavier J.
Published: January 2005

The infrared and Raman spectra of penta-deutero-fluoro-benzene have been measured and a set of assignments for the vibrational fundamentals is proposed. These are shown to be consistent with the present assignments of C6H5F, C6D6, and C6D5H by application of the product and inequality rules.
Quantitative Relations in the Mass Spectra of n-Paraffins
Authors: Coggeshall Norman D.
Published: January 2005

The mass spectra of n-paraffins in the C6 to C30 range have been examined for quantitative relations that must be predicted by any theory of ion formation by electron impact. An ion sum C(M, n) is defined as the sum of the normalized intensities of all ions of n carbon atoms from a n-paraffin of M carbon atoms. The molar yield Y(M, n) per unit of ionizing current will be MC(M, n). It has been observed that for large ions from large molecules the yield is independent of M or n but proportional to (M—n). Yields for smaller ions, i.e., n between 3 and 15, are linear with M but not proportional to M. The yields in this region may be expressed as Y(M,n)=An4e−bn(M−n′)where A and b are constants, one set applying for 3≦n≦10 and another set applying for 10≦n; the n′ values are constants, each depending upon the associated n. The observations indicate that the details of the fragmentation process for n-paraffins depend primarily upon the type of molecular skeleton, i.e., straight chain, single valence carbon-carbon linkages and secondarily upon the size of the molecule.
Dynamics of the Quasi-Linear Molecule
Authors: Thorson Walter R. , Nakagawa Ichiro
Published: January 2005

Calculations of energy levels, eigenfunctions, dipole transition moments, and other significant properties have been made for a phenomenological model of a two-dimensional harmonic oscillator with a superposed barrier at the minimum of the harmonic potential. A high-speed electronic digital computer was employed. The method of calculation does not involve perturbation theory and converges rapidly for all barrier heights. The problem concerns the behavior of the degenerate bending vibration of a linear triatomic molecule, for example, when a potential barrier is introduced at the linear configuration. In the limit of a high barrier, the motion is that of a ``bent'' molecule with rotational motion superposed on the bending vibration about the minimum of potential energy. Results for moderate to low barriers, and those for anharmonic vibration in a well with no barrier, show that the rigid classification of molecules as ``linear'' or ``bent'' is not possible in some cases and that the intermediate case of the ``quasi-linear'' molecule must be considered. The dynamical behavior of such anharmonic motion and its interaction with other vibrations have been investigated, and the primary identifying characteristics of the quasi-linear molecule delineated.

The analytical method of solution used has also been applied successfully to the one-dimensional barrier problem.
Dielectric Constants of Imperfect Gases. I. Helium, Argon, Nitrogen, and Methane
Authors: Johnston D. R. , Oudemans G. J. , Cole R. H.
Published: January 2005

Measurements from 1 to 100 atm have been made at one or more temperatures between —30° and 70°C by a special transformer ratio arm bridge operating at 10 kc; derived values of the Clausius-Mossotti function are of sufficient precision (0.1%) to justify comparison with theoretical pair fluctuation, polarizability and multipole moment interaction effects at higher densities. Helium shows a decrease of 0.3% and argon an increase of 0.1% in C-M at 100 atm, while nitrogen and methane show somewhat larger positive effects, especially at lower temperatures. A decreased effective polarizability of atom pairs at small distances is discussed as a possible explanation of the data for helium and argon, while the effect in nitrogen is consistent with quadrupole-induced dipole moments of pairs. A theory of octupole-induced dipole interactions is shown to be capable of explaining the methane results with plausible estimated values of the octupole moment.
On the Theory of the Critical Point of a Simple Fluid
Authors: Green Melville S.
Published: January 2005

The consequences of a new system of integral equations for the theory of the critical point are discussed. Reasons are given for believing that the fundamental assumption of the Ornstein-Zernicke theory about the direct correlation function is incorrect.
Ensembles of Maximum Entropy
Authors: Mayer Joseph E.
Published: January 2005

A theorem is stated and proved. The theorem considers the various possible probability density functions, WN, in the phase space of all the N molecules of a system, defined for an ensemble for which known mechanical properties require a given set of reduced probability densities, wn, for small numbers of molecules n<n0. The theorem states that the function, WN, of maximum entropy is that with the simplest possible correlations between the molecules consistent with the restraint imposed by the fixed wn, n<n0. It is then shown that the course of the negative entropy flow in a real ``isolated'' system undergoing spontaneous change is a flow of negative entropy into the correlation functions of many molecules followed by the destruction of these negative entropy terms due to the random time dependent fluctuations at the container walls.
Molecular Friction in Dilute Gases
Authors: O'Toole J. T. , Dahler J. S.
Published: January 2005

General formulas have been derived for the molecular friction coefficients of a dilute gas. The velocity and temperature dependencies of these coefficients are examined in detail for several choices of the pair interaction potential. Also we have considered the frictional loss of kinetic energy and, for one special case, the dissipation of molecular internal angular momentum. The concepts of free path length and collision frequency are extended to nonrigid molecular models.
Flow Equations and Frames of Reference for Isothermal Diffusion in Liquids
Authors: Kirkwood John G. , Baldwin Robert L. , Dunlop Peter J. , Gosting Louis J. , Kegeles Gerson
Published: January 2005

Equations for testing Onsager's reciprocal relations for isothermal diffusion depend on the frame of reference chosen for the flows. This subject is considered for certain frames of reference, as is the problem of measuring diffusion coefficients when there is a change of volume on mixing. Frames of reference discussed are those moving with the local center of mass, the local center of volume, the local velocity of the solvent (or of any single component), and that fixed on the diffusion cell. Multicomponent systems, both of strong electrolytes and nonelectrolytes, are considered. An expression is derived which relates the flow of a component in the cell-fixed frame of reference to the flows in any other frame of reference when there is a change of volume on mixing. This relation is used to show that a flow relative to the cell becomes identical to that in the volume-fixed frame as the initial differences in concentration within the diffusion cell are made sufficiently small. Throughout this article a special effort has been made to present derivations and final equations in a form well adapted for use in experimental work.
Structure of the Isobutane Molecule; Change of Dipole Moment on Isotopic Substitution
Authors: Lide David R.
Published: January 2005

The microwave spectra of 5 isotopic species of isobutane have been measured and analyzed. The isobutane molecule is shown to belong to point group C3v. The structural parameters determined by the substitution method are r(CC)=1.525 A, ≰CCC=111.15°, r(CH)=1.108 A (tertiary), r(CH)=1.09–1.10 A (methyl), ≰HCH=107.5°—109.5°. The structure is compared with that of other hydrocarbons, and it is suggested that a small systematic difference exists between CC distances determined by microwave and electron diffraction methods. Accurate Stark measurements show that the dipole moment of (CH3)3CD is 6.5%±0.9% higher than that of (CH3)3CH.
A Theory for the Triplet-Triplet Absorption Spectra of Porphyrins
Authors: Gouterman Martin
Published: January 2005

The triplet excited states of porphin are classified as either singly or doubly excited electron configurations. The latter are discussed in detail in terms of a circular box model with electron interaction plus a perturbation due to the actual molecular shape. The energy and intensity of the triplet-triplet transitions from the lowest triplet to these doubly excited states are predicted to consist of: (1) transitions to a pair of states of energy ∼25 000 cm-1; (2) transitions to a group of four states of energy ∼20 000 cm-1; and a transition to a state of energy ∼18 000 cm-1. The first two groups are predicted to share equally an intensity half that of the porphin Soret band, while the last transition is weakly forbidden. The predictions compare reasonably well with experiment. In addition, a metastable molecular quintet is predicted, with a transition energy to the lowest triplet state slightly smaller than any observed triplet-triplet transition.
Normal Vibrations of the Polymer Molecules of Helical Configuration
Authors: Tadokoro Hiroyuki
Published: January 2005

A method suitable for numerical calculations of the normal vibrations of helical molecules is derived by the use of GF-matrix method. The method is described for the case of the isolated infinite helical molecule in which the one-dimensional crystallographic repeat unit contains n chemical units and m turns (one chemical unit contains p atoms). It is shown that the optically active fundamental frequencies of such molecules can be obtained by solving the secular equations for A, B, E1, and E2 species, the maximum orders of which are 3p—2, 3p, 3p—1, and 3p, respectively. This method can be also applied to the cases of infinitely extended planar zigzag chains such as polyethylene and cyclic molecules such as trioxane, etc., as special cases. As examples of application of this method, calculations of the skeletal vibrations of a simple model of polyoxymethylene molecule under the group D(10π/9) and of the planar zigzag chain of carbon atoms are given.
Forces in Molecules. I. Application of the Virial Theorem
Authors: Clinton William L.
Published: January 2005

It is shown that the virial theorem can be used to derive a force constant expression that sheds new light on the process of molecular binding. In connection with the latter the quantum-mechanical virial theorem is derived in such a way as to be useful in discussing molecular applications in which the Born-Oppenheimer approximation is applied.
Pressure Effects in Nickel Dimethylglyoxime and Related Chelates
Authors: Zahner J. C. , Drickamer H. G.
Published: January 2005

The effect of pressure on the absorption peak characteristic of the solid phase of certain metal chelates has been measured for Ni(DMG)2, Pd(DMG)2, Pt(DMG)2, Ni nioxime, Pd nioxime, Ni benzoxime, and Ni heptoxime. The peak shifts strongly red with pressure. At high pressure the shift levels off for nickel, tends to reverse for palladium and reverses strongly for plantinum. There is considerable pressure broadening. These and other related observations are consistent with the assignment of the transition as from the A1g (or A1g and Eg) ground state to the A2u (pz) excited state.
Mass Spectrometric Study of Heats of Dimerization of Alkali Chlorides
Authors: Milne Thomas A. , Klein H. Michael
Published: January 2005

The heats of sublimation of the important species in equilibrium with the five alkali chlorides have been determined using the Bendix time-of-flight mass spectrometer. The mass spectrometrically determined differences between the heats of sublimation of monomer and dimer have been combined with the best available value for the monomer heat of sublimation to calculate the dimerization energies for all five salts. For LiCl a trimerization energy was also determined. These results are compared with the results of previous studies.
Methyl Affinities Determined by Photolysis of Azomethane
Authors: Steel C. , Szwarc M.
Published: January 2005

The thermal decomposition of acetyl peroxide forms acetate radicals which decarboxylate into methyl radicals. The reaction products may result, therefore, either from methyl radicals or from acetate radicals which decarboxylate simultaneously as they interact with the substrate. To identify the reacting species, reactions previously investigated in an acetyl peroxide system were reinvestigated using the photolysis of azomethane as the source of radicals. The results prove that at least in hydrocarbon solvents methyl radicals, and not acetate radicals, are the reacting species in the acetyl peroxide system. Furthermore, it was shown that photolysis of azomethane in solution provides us with a clean and simple system to study reactions of methyl radicals.
Dynamical Jahn-Teller Effect in Hydrocarbon Radicals
Authors: Hobey W. D. , McLachlan A. D.
Published: January 2005

The first part of this paper shows how the ordinary Born-Oppenheimer approximation for separating nuclear and electronic motion can be adapted to a degenerate electronic state. To set up equations of motion for the dynamical Jahn-Teller effect in their simplest form we use vibrational amplitudes associated with special linear combinations of the degenerate electronic wave functions, chosen to vary as slowly as possible with nuclear displacements. We also discuss briefly the symmetry-forbidden electronic transitions allowed by a Jahn-Teller distortion. In the second we make molecular orbital calculations of the energies and distorted shapes of some aromatic hydrocarbon molecules. The differences in energy between the distorted and symmetrical shapes (in kcal/mole) are cyclobutadiene 11.43; cyclopentadienyl 1.414, cycloheptatrienyl 0.859; benzene negative ion 1.077; triphenylene and coronene negative ions 0.385 and 0.299. In the last three each shape of minimum energy is separated from two equivalent ones by a small potential barrier, respectively, 0.000, 0.001, and 0.002. The ground state of each radical is doubly degenerate, and it can oscillate about a continuous series of distorted shapes. In the excited 1E1u+ and 3E1u+ states of benzene the distortions are much smaller, and the CC bonds probably bend rather than stretch.
Frequency Distribution and the Specific Heat of NaCl at Low Temperatures
Authors: Arase Elizabeth M. , Hatcher Robert D.
Published: January 2005

Using the Kellerman model of the NaCl crystal, the eigenfrequencies at 0°K are found from those at room temperature by a first-order perturbation theory, which is developed here. From this the frequency distribution at 0°K is obtained and is compared with the room-temperature frequency spectrum. The specific heat and apparent Debye temperatures below 100°K based on both distributions as well as a linearly weighted average are given.
On the Molecular Nature of the Dielectric Anomalies in Thiourea
Authors: Calvo Crispin
Published: January 2005

Of the four dielectric anomalies in thiourea, three are shown to be correlated with the disordering of the molecules in the crystal. This disordering involves both a relative rotation and a translation of the molecules between potential minima. One of the other anomalies, the high one in temperature, is shown to result from a translation of the molecules within the unit cell. Lattice parameter measurements as a function of temperature confirm that the lowest transition is of first order and show only a change in slope at the highest transition. An electrostatic model based upon the electronic resonance structures of thiourea is used to discuss the binding energy of the molecules in the crystal, the vibration of the molecules, the equilibrium orientation of the molecules in the unit cell, and the spontaneous polarization of the crystal. A simple statistical model based upon two interpenetrating nonidentical sublattices reveals a disordering of the molecules from 0°K to 178°K and yields the first-order transition together with the two ferrielectric regions of temperature.
On the Absorption Spectrum of CF2 and Its Vibrational Analysis
Authors: Mann D. E. , Thrush B. A.
Published: January 2005

The flash photolysis of CF2Br2 has been used to obtain the absorption spectrum of the CF2 radical. The principal features of the spectrum are a progression of the upper state bending frequency, and a number of weak bands which are shown to arise from a vibrationally excited lower state. There is no evidence for transitions involving stretching vibrations. The vibrationless origin of the system (v1′=0, v2′=0, v1″=0, v2″=0) is shown to lie at approximately 37 695 cm—1. The deformation frequencies of the lower and upper states are about 660 and 500 cm—1, respectively.
Infrared Spectra of Crystalline CD3Cl and CD3Br
Authors: Dows David A.
Published: January 2005

Infrared spectra have been obtained for deuterated methyl chloride and bromide. The region covered includes all fundamental vibrations, many of which showed splittings similar to those observed for the normal methyl halides. [See D. A. Dows, J. Chem. Phys. 29, 484 (1958).] Assignments are presented, and librational frequencies in the methyl halides are summarized.
Critical Opalescence of Polystyrene in Cyclohexane
Authors: Debye P. , Coll H. , Woermann D.
Published: January 2005

Light scattering measurements on the system cyclohexane-polystyrene (molecular weight range 69 000 to 1 000 000) show an angular dissymmetry of critical opalescence in essential agreement with theory. The interaction range between polymer segments as calculated from the data appeared to be considerably smaller than the radius of gyration of the polymer coil. The dependence of critical temperature and concentration on the molecular weight is shown.
Heat Capacity of Ice at Low Temperatures
Authors: Flubacher P. , Leadbetter A. J. , Morrison J. A.
Published: January 2005

The heat capacity of normal hexagonal ice has been measured over the temperature range 2° to 27°K with an estimated precision varying between ±2% at the lowest temperatures and ±0.2% at the higher temperatures. The results agree satisfactorily with those of earlier measurements in the region T> 10°K, and do not significantly affect the value of the residual entropy of ice calculated by Giauque and Stout [W. F. Giauque and J. W. Stout, J. Am. Chem. Soc. 58, 1144 (1936)]. Although the new results do not influence the existing thermodynamic description of ice, they provide information which is important in understanding its vibrational properties. In the first place, extrapolation of the results to T=0°K yields a value of Θ0, the Debye characteristic temperature corresponding to continuum behavior. This is found to agree satisfactorily with Θ (elastic) estimated from the elastic constants of ice. In the second place, complete ΘD(T) curves can be constructed, and an examination of these, computed for different sizes of vibrational unit, enables the gross features of the lattice frequency spectrum of ice to be determined. The conclusion reached is that the three components of the spectrum, due respectively to translational and rotational vibrations of the water molecule and to intramolecular vibrations, are well separated. The contribution of the librational modes to the thermodynamic properties can be approximated rather well by a single frequency of 620 cm—1.
Infrared and Raman Spectra of Fluorinated Ethanes. XIII. 1,2-Difluoroethane
Authors: Klaboe Peter , Nielsen J. Rud
Published: January 2005

The infrared absorption spectra of CH2F–CH2F in the gaseous, liquid, and solid states have been obtained with a Perkin-Elmer double-pass spectrometer equipped with CsBr, NaCl, and LiF prisms. While the gas was studied in the spectral range from 6000 to 300 cm—1, the liquid was examined from 6000 to 650 cm—1 and the solid from 3500 to 350 cm—1. In addition, the infrared spectrum of the gas has been recorded at five different temperatures between 25°C and 180°C, and some of the absorption bands have been studied in solution in solvents of different polarities. The Raman spectrum of the liquid at —25°C and 35°C has been photographed with a 3-prism glass spectrograph and polarization measurements have been made. In all three states of aggregation the compound exists as a mixture of rotational isomers. The two isomeric forms (trans and gauche) are about equally stable in the gas, while the gauche configuration is more stable in the liquid state. Tentative assignments have been made of all fundamentals except the lowest fundamental of the trans isomer.
Lattice Heat Capacity of the Rare Earths. Heat Capacities of Yttrium and Lutetium from 15–350°K
Authors: Jennings L. D. , Miller R. E. , Spedding F. H.
Published: January 2005

The heat capacities of lutetium and yttrium have been measured and are found to have the same dependence on a reduced temperature as does that of lanthanum. The lattice heat capacities are given by θ values of 130.7, 166.0, and 213.7 for La, Lu, and Y and the corresponding electronic heat capacities are given by γ values of 100, 95, and 85×10—4 joules/g atom-deg2.