bluuebunny/crossref_metadata_2025 huggingface dataset:
Relative Signs of the Nuclear Spin Coupling Constants in Propylene Oxide and Indene Oxide
Authors: Elleman Daniel D. , Manatt Stanley L. , Pearce Claude D.
Published: January 2005

The 60-Mc/sec high-resolution NMR spectrum of propylene oxide was analyzed as an ABCD3 nuclear spin system in the conventional iterative manner utilizing in addition double resonance to decouple the D3 (methyl group) protons from the ABC protons. A fit was obtained by two sets of parameters whose main difference was that either both long-range couplings JBD and JCD are positive with respect to the other couplings or only JCD is negative. By use of a weak perturbing rf field to irradiate a particular resonance transition it was determined that JCD has a different sign than the other couplings.

The 60-Mc/sec spectrum of the protons of the five-membered ring of indene oxide (II) was analyzed as an ABCD system with the aid of triple-irradiation experiments in which the long-range couplings of the A, C, and D protons with the aromatic ring protons were destroyed by a large rf irradiation applied at the resonance position of the aromatic protons while a second weaker perturbing irradiation was applied at particular lines in the ABCD spectrum. The results of these experiments determined the energy level scheme and suggested that if this spectrum is truly first order then all the coupling constants in the four spin system are positive except JCD. However, complete iterative analysis using the Swalen and Reilly program showed the spectrum of II was definitely not first order and that JAD is almost zero and JBC very small. The following sets of parameters were found for I and II. JABJACJADJBCJBDJCDδAδBδCδDI+3.88+2.57+5.15+5.37+0.52−0.362.8492.5892.2791.214II+2.90+1.32−0.01+0.12+3.11−18.224.1393.9833.1422.879 The spin—spin couplings are in cycles per second and chemical shifts in parts per million downfield from tetramethylsilane.

Stereochemically the H–C–C–C–H couplings in II and the positive H–C–C–C–H coupling in I are similar, i.e., the protons on the oxirane ring are related in what can be considered a ``trans'' manner to the carbon—carbon bond joining the methyl or methylene group to the oxirane ring. The results from the rigid molecule II suggest that this particular long-range coupling involving four saturated bonds is positive when the protons are in an ``anti—trans'' relation or furthest away and near zero when the protons are in a ``syn—trans'' relation or nearer. The magnitudes and signs of the H–C–C–C–H couplings found in I and II are discussed in some detail and compared with other reported similar long-range couplings.

The description of the field-frequency lock spectrometer used in this work is given. With this system it was possible to detect excursions of the field-frequency setting of the order of 1–2 parts in 1010.
Mass-Spectrometric Study of Ions at Near Atmospheric Pressures. I. The Ionic Polymerization of Ethylene
Authors: Kebarle P. , Hogg A. M.
Published: January 2005

An apparatus is described which allows the mass-spectrometric analysis of ions produced by the alpha-particle irradiation of gases in the pressure range 5–200 Torr. The ions emerge from the field free ionization chamber by effusion. This method of sampling should give an (approximate) picture of the steady state ionic concentration. A simplified kinetic treatment based on the steady state assumption can explain the experimental results.

The mass spectrum of ethylene at 40 Torr pressure is very complex. It extends beyond the highest mass (215) measured. The major ions are CnH2n−1+.

A simplification of the reaction system is achieved with a dilution—charge-exchange technique. The ethylene spectrum obtained from 1% ethylene in xenon gives the ionic polymerization initiated by C2H4+. The most abundant series is (C2H4)n+. Xenon is deactivating the excited addition products.

Low ionization potential impurities or reaction products, present in less than parts-per-thousand concentration, can still change the ionic population profoundly. This is of significance to conventional radiolysis work.

Temperature increase from 20°—60°C has little effect on the ethylene spectra. Other gases or gas mixtures show large changes because of cluster rearrangement.
Transition Probabilities of the Nuclear Pure Quadrupolar Relaxation of 35Cl in Paradichlorobenzene
Authors: Pissanetzky Sergio
Published: January 2005

A measurement of the transition probabilities W1 and W2 for the pure quadrupolar relaxation of 35Cl in paradichlorobenzene is interpreted in terms of the Woessner—Gutowsky theory.

A supposition about two-torsional oscillation frequencies contributing simultaneously to the relaxation is found to produce a good agreement with experiment at a temperature of 77°K. This is shown to be a transition temperature, because at lower temperatures the relaxation is governed principally by the oscillation of lower frequency, while at higher temperatures it is governed by the oscillation of higher frequency.
Raman Spectra of Liquid AlCl3·KCl and AlCl3·NaCl
Authors: Balasubrahmanyam K. , Nanis L.
Published: January 2005

The Raman spectra of AlCl3·KCl (solid and liquid) and AlCl3·NaCl (liquid) were recorded using a Cary 81 Raman spectrophotometer. Both solid and liquid AlCl3·KCl exhibit nine Raman lines. For liquid AlCl3·NaCl, only four Raman lines were observed. Polarization measurements indicate the existence of the complex species AlCl4—, with a distorted tetrahedral structure (C2v) in solid and liquid AlCl3·KCl and a regular tetrahedral structure (Td) in AlCl3·NaCl. The force constants for AlCl4— ion were calculated using a generalized valence force.
Frequency Shifts and Band Contours of Vibrational Transitions of Vapors Trapped in High-Density Polyethylene. The ν3, ν5, ν6, ν5−ν3, and ν2−ν6 Bands of CHCl3 and the ν2, ν3 Modes of CS2
Authors: Rothschild Walter G.
Published: January 2005

Frequency shifts and band contour changes of far-infrared vibrational transitions of chloroform and carbon disulfide vapor upon entrapment in high-density polyethylene above the glass transition temperature have been studied between 240 and 420 cm−1. The data were applied to elucidate the interactions between the trapped molecules and the polymer. The ν6, ν5, ν3 fundamentals and the ν2−ν6, ν5−ν3 difference bands of chloroform and the ν2, ν3 fundamentals of carbon disulfide were measured with the molecules in the free vapor state and each included in polyethylene. The two difference bands and the ν5 fundamental of chloroform undergo large red shifts upon entrapment of the molecules in polyethylene. A qualitative evaluation of the red shift of the ν5 band based on the Kirkwood—Bauer—Magat theory shows that the interaction between the trapped chloroform and the polyethylene can be described in terms of a polarization of the polymer by the dipoles of chloroform. There is no appreciable amount of localized bonding between chloroform molecules or chloroform and polyethylene. The carbon—chlorine deformation modes ν6 and ν3 of chloroform undergo slight blue shifts upon entrapment in polyethylene. Based on Buckingham's quantum-mechanical model of intermolecular interactions, the smallness of these shifts may be explained by the relatively minor degree of anharmonicity of the ν6 and ν3 modes compared to that of the other modes of chloroform. Two hot bands, which are hidden under the R and P branches of the ν2 mode of free carbon disulfide molecules, appear in the spectrum of the ν2 mode of the trapped molecules. Intensity measurements indicate that the hot bands arise from the levels ν2 and 2ν2, respectively. It is shown that the solvent shifts of the ν2 and ν3 modes of carbon disulfide in polyethylene, which amount to 2.8 and 8.0 cm−1, are insufficient data to afford a quantitative evaluation of the intermolecular potential in Buckingham's model.
Pulse Radiolysis Studies. VII. The Absorption Spectra and Radiation Chemical Yields of the Solvated Electron in the Aliphatic Alcohols
Authors: Sauer Myran C. , Arai Shigeyoshi , Dorfman Leon M.
Published: January 2005

The absorption spectra of the solvated electron in five aliphatic alcohols have been determined by the pulse radiolysis method. For the alcohols: ethylene glycol, methanol, ethanol, n-propanol, and isopropanol, the absorption maxima show a red shift with decrease in the value of the static dielectric constant. The absorption maxima for these alcohols are, respectively, 5800, 6300, 7000, 7400, and 8200 Å. The molar extinction coefficient at the maximum and the oscillator strength of the broad absorption band has been determined for each alcohol.

The radiation chemical yields of the solvated electron in these irradiated alcohols as determined by pulse radiolysis are, respectively, 1.2, 1.1, 1.0, 1.0, and 1.0 per 100 eV.

The correlation between the transition energy for optical excitation of the solvated electron and the dielectric behavior of the liquid is discussed in terms of the theory.
Viscoelastic Properties of Monodisperse Polystyrene
Authors: Tobolsky A. V. , Aklonis J. J. , Akovali G.
Published: January 2005

The viscoelastic properties of five monodisperse polymer samples of polystyrene ranging in molecular weight between 80 000 and 270 000 were studied and accurate values of ηt, Je, τm, and Em were obtained. It is shown that the dependence on molecular weight of these quantities is very different from that predicted by the Rouse—Bueche theory or by the Ferry—Landel—Williams modification of this theory.
Exchange Effects on the Electron and Hole Mobility in Crystalline Anthracene and Naphthalene
Authors: Silbey Robert , Jortner Joshua , Rice Stuart A. , Vala Martin T.
Published: January 2005

In this paper we present the results of calculations of the electron and hole band structure of crystalline anthracene and naphthalene in the tight binding approximation, and of the mobility tensor in the constant-free-time and constant-free-path approximations. This treatment differs from previous formulations by inclusion of the effects of intermolecular electron exchange and of vibronic coupling (in the weak coupling scheme). The bandwidths were found to be of the order of 0.02 eV and smaller, and the mobility data were found to be consistent with the band scheme. The predicted mobility in the c′ direction is found to be in good agreement with experiment, in contrast to previous treatments.
Influence of Electric and Magnetic Fields on the Microwave Dielectric Constant of a Liquid Crystal with a Positive Dielectric Anisotropy
Authors: Carr E. F.
Published: January 2005

The dielectric constant and loss in the anisotropic and normal liquid phases of anisal-p-aminoazobenzene were measured at frequencies of 6 and 24 kMc/sec. Measurements were made with an external magnetic field parallel and perpendicular to the microwave electric field at both frequencies while the measurements in the presence of an external electric field were made at only 6 kMc/sec with the external electric field parallel to the microwave electric field. Results in the presence of an external magnetic field were similar to those for p-azoxyanisole and anisaldazine which have a negative dielectric anisotropy. Measurements in the presence of an external electric field indicate that the alignment of the molecules due to low frequency ac fields is comparable to that produced by magnetic fields providing saturation is reached. Disturbances which were due to an electric field appeared to have an appreciable effect on the alighment when dc fields were applied, but this was not observed for ac fields with frequencies between 20 and 300 000 cps.
Internal Vibronics in Terbium Compounds—A Cooperative Phenomenon
Authors: Yatsiv S. , Ehrenfreund E. , El-Hanany U.
Published: January 2005

The observation of absorption and emission vibronics in Tb3+ compounds is reported. This follows a similar analysis of Gd3+ compounds and a comparison is made between the two cases. A theoretical model based on a cooperative approach to these transitions is developed. This model yields the activity of vibrational modes involved in internal vibronics. It also gives the relative intensity of a vibronic compared to its parent electronic transition as a function of the particular rare-earth (RE) ion and of its physical surroundings.
Entropy and Related Thermodynamic Properties of Acetonitrile (Methyl Cyanide)
Authors: Putnam William E. , McEachern Douglas Marvin , Kilpatrick John E.
Published: January 2005

The heat capacity, the heats of fusion and vaporization, and the entropy have been measured for acetonitrile. This substance has a triple point at 229.315±0.020°K (ΔH=1951.96±0.40 cal/mole), a broad transition at 216.9±0.1°K (ΔH=214.6±0.3 cal/mole), and a heat vaporization at 298.15°K of 7941 cal/mole. The standard entropy of the ideal gas at 25°C was found to be 58.67±0.20 cal/deg·mole. The best value of the entropy calculated from statistical mechanics, 58.01 cal/deg·mole, shows a surprisingly large discrepancy from our experimental results.
Ground States of Conjugated Molecules. I. Semiempirical SCF MO Treatment and Its Application to Aromatic Hydrocarbons
Authors: Chung Alice L. H. , Dewar Michael J. S.
Published: January 2005

The π-bonding energies and resonance energies for a series of monocyclic polymethines (CH)n, and several benzenoid and nonbenzenoid hydrocarbons are calculated by the Hückel, Pople, and SPO methods. Special attention is paid to the formulation and definition of such energy terms. For simplicity equal bond lengths are assumed in each case; in the case of the polymethines, the planar configurations of regular polygons are taken.

The calculated π-bonding energies of 11 benzenoid hydrocarbons are combined with experimental heats of formation and an assumed carbon—hydrogen bond energy to obtain estimates of the bond energy of a carbon—carbon σ bond in an aromatic ring. The values obtained for the eleven compounds agree very closely, implying that a good estimate of the heat of formation of such hydrocarbons can be obtained by adding the σ-bond energies to the calculated π energy. This approach is used to estimate resonance energies of the aromatic hydrocarbons.

The resonance energies of the polymethines are found to alternate strongly, regardless of the choice of methods used; the values are uniformly larger for rings with 4n+2 π electrons than for rings with 4n π electrons. In the Pople and SPO cases, bond alternation is predicted for all the rings with 4n carbon atoms as well as for those with 4n+2 carbon atoms starting at n=4.

For certain nonbenzenoid hydrocarbons the calculated resonance energies are only in fair agreement with experimental findings. For most, agreement is satisfactory.
Focusing and Orientation of Symmetric-Top Molecules with the Electric Six-Pole Field
Authors: Kramer K. H. , Bernstein R. B.
Published: January 2005

The electric six-pole field is employed for focusing of beams of symmetric-top molecules via the first-order Stark effect. Molecules capable of a specified degree of orientation of dipole moment with respect to an electric-field vector can be selected according to the voltage applied to the electrodes of the six-pole field. The rotational angular momentum of the focused molecules can also be well aligned with the field. Experiments with CH3I and CHI3, prolate and oblate tops, have been carried out to illustrate the method.
Photodesorption
Authors: Adams R. O. , Donaldson E. E.
Published: January 2005

Monochromatic radiation with a wavelength between 2000 and 6000 Å is shown to desorb CO from surfaces of Fe, Ni, and Zr. The desorption efficiency has a maximum at 2700 Å for Ni, at less than 2500 Å for Zr, and in the visible region for Fe. Photodesorption from W and Mo was not detected. A suggested mechanism for photodesorption indicates that valuable information concerning surface binding can be obtained from refined measurements.
Electronic Structure of Ni2+ in MgF2 and ZnF2
Authors: Ferguson J. , Guggenheim H. J. , Kamimura H. , Tanabe Y.
Published: January 2005

The absorption spectra of nickel (II) in MgF2 and ZnF2 are reported. The important feature of the spectra is that the first spin-allowed absorption band shows strongly polarized line structure. From its polarization, the mechanism of the absorption for this line structure has been determined to be magnetic dipole. Furthermore, together with its temperature dependence, symmetry assignments have been made for the fine structure of 3T2 and the ground state. The energy separations and assignments of the ground state thus determined are compatible with the results of electron spin resonance. Choosing two parameters of the orthorhombic field so as to fit the energy separations of the ground state, each energy level of 3T2 under the combined action of the spin orbit force and orthorhombic fields has been calculated as a function of two remaining parameters and compared with experiment. The values of the four parameters and the discrepancy with experiment are discussed. It is shown that the effective Hamiltonian approach for 3T2 is as good as the configuration interaction approach including all the states of d8 electron configuration, provided the second-order effect of the spin—orbit interaction is included. As one of possible mechanisms to remove the discrepancy with experiment within the framework of the crystal field theory, Jahn—Teller distortions of the 3T2 state are considered.
High-Temperature Microwave Spectroscopy : AlF and AlCl
Authors: Lide David R.
Published: January 2005

Microwave transitions of gaseous AlF and AlCl have been studied in a high-temperature spectrometer. The molecular constants obtained for AlF are: Be=16 562.56 Mc/sec,αe=148.40 Mc/sec,re=1.65437 Å,(eqQ)A1=−37.6 Mc/sec,μ=1.53 D; for Al35Cl:Be=7312.74 Mc/sec,αe=48.03 Mc/sec,re=2.12983 Å,(eqQ)A1=−29.2 Mc/sec,(eqQ)C1=−8.8 Mc/sec; for Al37Cl:Be=7140.69 Mc/sec,αe=46.34 Mc/sec. The nature of the bonding in aluminum halides is discussed; it is concluded that the bonds are highly ionic and that the Al orbitals are sp hybrids. The details of the high-temperature spectrometer are given.
Paramagnetic Resonance Studies of Bonding in Vanadyl and Molybdenyl Metal Complexes
Authors: DeArmond Keith , Garrett Barry B. , Gutowsky H. S.
Published: January 2005

Electron spin resonance data for [VOCl5]3— and [MoOCl5]2— in dilute single crystals are reported and and analyzed to give the spin Hamiltonian parameters for these complexes. A molecular orbital formulation is given for the spin Hamiltonian parameters, and terms dependent on spin—orbit interactions near ligand nuclei are found. This formulation is applied to the experimental results by means of an empirical method including radial expansion effects, and estimates of certain LACO—MO coefficients are obtained. The bonding in [VOCl5]3—, [VO(H2O)5]2+, and [MlOCl5]2— is discussed in terms of these LCAO—MO coefficients.
Diffusion Versus Surface Limitations in Vapor-Solvent Growth of Germanium
Authors: Jona F.
Published: January 2005

Measurements of transport rates as functions of pressure in the systems germanium—iodine and germanium—bromine have been carried out. The results are discussed in terms of Lever's theory for diffusive transport. It is concluded that while the germanium—iodine system is highly diffusion limited, the germanium—bromine system is noticeably surface controlled.
Pi-Electron Correlation in the Carbon Negative Ion Valence State
Authors: Hermann Robert B.
Published: January 2005

A configuration-interaction treatment has been carried out for the carbon negative ion in the 1s22s2p4(V3) valence state. Starting with the Hartree—Fock atom and treating only the two 2pz electrons, 0.617 eV or an estimated 80% of the correlation energy in the 2pz valence state geminal is accounted for. Some implications for pi-electron theory are discussed.
Paramagnetic Resonance Absorption by Divalent Vanadium Ion in Cadmium Dichloride
Authors: Chan I. Y. , Doetschman D. C. , Hutchison Clyde A. , Kohler Bryan E. , Stout J. W.
Published: January 2005

Paramagnetic resonance absorption by V2+ ions in CdCl2 single crystals has been investigated at 77° and 4.2°K. The experimental results are described by the spin Hamiltonian H=+H·g·|β|S+S·T·S+I·A·S,in which S=32,gzz≡g‖=+1.9661,σ{g‖}=0.0009,gxx=gyy≡g⊥=+1.9704,σ{g⊥}=0.0006,Tzz/hc≡D/hc=−0.2077 cm−1,σ{D/hc}=0.0002 cm−1,Txx/hc=−Tyy/hc≡E/hc=0.0000 cm−1,σ{E/hc}=0.0002 cm−1,Axx/hc=Ayy/hc=Azz/hc≡A/hc=±0.00767 cm−1,σ{A/hc}=0.00006 cm−1,where x, y, z refer to principal axes of the tensors, the trigonal axis of the crystal is the z axis, σ is the standard deviation, and the parameters are given for 77°K.
Nuclear Quadrupole Coupling in Polyatomic Molecules
Authors: Kern C. W. , Karplus M.
Published: January 2005

The Gaussian-transform method has been applied to the evaluation of the deuteron and nitrogen-14 quadrupole coupling constant (eqQ/h) with the various minimal and extended basis-set SCF—LCAO—MO functions that are available for the linear polyatomic molecules DCN, C2D2, DF2—, and N3—. Comparisons are made between calculations neglecting and including the three-center integral contributions. The coupling constant is found to be quite sensitive to the choice of basis orbitals, particularly those responsible for the form of the valence-shell charge density. This suggests that the quadrupole coupling constant in polyatomic molecules is a useful criterion for testing the wavefunction obtained in approximate calculations. Of particular interest is the variation in the (eqQ/h)D results for DF2—, which points out the need for an experimental coupling constant measurement for this hydrogen-bonded species.
Mössbauer Studies of Iron Organometallic Complexes. IV. Sign of the Electric-Field Gradient in Ferrocene
Authors: Collins R. L.
Published: January 2005

The quadrupole splitting of 57Fe Mössbauer spectra gives the magnitude, but not the sign, of the electric-field gradient. The sign can be determined by magnetically perturbing the energy levels, such that one line splits into a triplet and the other line splits into a doublet. A first-order perturbation treatment for the axially symmetric electric-field gradient case is given for powdered samples. The method is applied to ferrocene, which has been the subject of many theoretical papers. A crystal-field treatment predicts a positive efg, and molecular orbital treatments predict negative efg's. At 40 kG applied, the two lines split clearly into a doublet and a triplet. The result agrees with the MO treatment. This also explains the essential vanishing of the efg in ferrocinium compounds.
Laser Phenomena in Europium Chelates. III. Spectroscopic Effects of Chemical Composition and Molecular Structure
Authors: Brecher C. , Samelson H. , Lempicki A.
Published: January 2005

The emission spectra of the tris and tetrakis forms of four β-diketone chelates of europium were studied in the solid powder, and in alcohol solution with and without dimethylformamide added. Partial dissociation of the tetrakis form was observed in solution. Effective site symmetries, subject to steric distortion, were derived for the tetrakis-chelated europium ion in the various hosts: D2d in pure alcohol, C4v in alcohol plus dimethylformamide, and C4v in the crystal. For the tris chelates, in both their hydrated and anhydrous forms, a number of different low-symmetry species were found to exist simultaneously in each host medium. The implications of these findings to the laser capabilities of the chelates are discussed.
Low-Temperature Specific Heat of Finely Divided Sodium Chloride
Authors: Barkman James H. , Anderson Richard L. , Brackett Thomas E.
Published: January 2005

The specific heats of two samples of finely divided particles of sodium chloride (specific surfaces 41.8 and 78.3 m2/g) have been measured from 4° to 20°K. The excess specific heat is found to be proportional to the specific surface S and to T2 with a constant of proportionality equal to 0.64×10−6 cal·g deg−3· m−2·mole−1. This result lies within the range of various theoretical predictions of the effect.
Virial Coefficients for the Hard-Core Gas in Two Dimensions
Authors: Hemmer P. C.
Published: January 2005

The fourth virial coefficient for a gas of hard disks is calculated by means of the virial theorem. The exact result is B4/b3=2–93/2π+10π−2, where b is the second virial coefficient. The numerical value for B4/b3 of 0.532232 confirms previous estimates obtained by Monte Carlo integration.

The weights of all four-point irreducible clusters are also recorded.
Secondary Ions in the Mass Spectrum of Propane
Authors: Ryan Keith R. , Futrell Jean H.
Published: January 2005

The secondary spectra arising from ionic reactions in propane at several mean ion energies are reported. The results are compared with computed values taken from results obtained by the elegant techniques developed by Lindholm. From the comparison a calculation is made for the secondary spectrum obtained by bombarding C3H8 with C2H4+ ions. Experiments using mixtures of C2D4 and C3H8 lead to an observed secondary-ion spectrum which is in good agreement with that calculated. A significant number of ionic fragments in the secondary spectrum appear to be formed by endothermic processes. It is assumed that translational energy supplies the required energy. Some appearance-potential measurements support this assumption. There appears to be some evidence for CH3— transfer when C3H8 is bombarded either by C2H5+ or C2H4+. In both cases there is also a competing H— transfer process.
Hydrazine—Water System. II. Nonequilibrium Phase Transformations
Authors: McMillan J. A. , Los S. C.
Published: January 2005

Although neither hydrazine nor water supercool to a large extent, their mixtures do. Aqueous solutions of hydrazine may be strongly supercooled and stabilized as rigid glasses. The values of the glass-transformation temperatures determined during warmup depend on the warmup rate, permitting the evaluation of mean values of the relaxation times characterizing the motions that are frozen in below such temperatures. The supercooled mixtures crystallize during warmup at temperatures that also depend on the warmup rate. The duration of the crystallization process exhibits a one-to-one correspondence with the temperature at which it occurs. The logarithm of the process duration varies linearly with the inverse of the absolute temperature permitting the evaluation of activation energies. Application of the theory of absolute reaction rates leads to the determination of entropy barriers. The correlation observed with the equilibrium phase transformations permits an interpretation of the processes of supercooling and crystallization during warmup. Detailed experimental results are discussed.
Electron Diffraction Study of the Structures of Ethane and Deuteroethane
Authors: Bartell L. S. , Higginbotham H. K.
Published: January 2005

An electron diffraction structure determination for ethane and deuteroethane has been carried out to study the magnitudes of primary and secondary deuterium isotope effects on bond lengths. Mean parameters and estimated standard errors for C2H6 were rg(C–H) = 1.1122±0.0012 Å, lg(C–H) = 0.0760±0.0010 Å, rg(C–C) = 1.5340±0.0011 Å, lg(C–C) = 0.0496±0.0010 Å, and ∠CCH = 111.0±0.2°. Corresponding parameters for C2D6 were rg(C—D) = 1.1071±0.0012 Å, lg(C—D) = 0.0668±0.0010 Å, rg(C–C) = 1.5323±0.0011 Å, lg(C–C) = 0.0517±0.0010 Å and ∠CCD = 111.0±0.2°. Shrinkage corrections have not been made for bond angles. A primary deuterium isotope effect of 0.0050±0.0006 Å was found for the carbon hydrogen bond. A possibly significant secondary effect was observed in which the C–C length in ethane exceeded that in deuteroethane by Δrg(1) = 0.0016±0.0007 Å. Some aspects of secondary isotope effects are discussed briefly.
Paramagnetic Resonance of the Phosphorescent States of Quinoline and Isoquinoline
Authors: Vincent James S. , Maki August H.
Published: January 2005

Paramagnetic resonance measurements are reported in solid solutions of quinoline, and of isoquinoline in durene under irradiation with ultraviolet light at 77°K. The fine structure of the magnetic resonance spectrum observed at 9.2 Gc/sec may be described by the spin Hamiltonian H=βH·g·S+DSz2+E(Sx2−Sy2), with S = 1. D, E, and the principal values of g are reported for each molecule. The principal axis systems of the zero-field tensors D are found to be displaced from the molecular axis system of durene in the host crystal in both the quinoline and isoquinoline doped crystals. The D axis systems are found to be rotated about an axis perpendicular to the molecular plane of durene. The principal axis systems of D and g are found to be the same within experimental error for the quinoline phosphorescent state. Hyperfine structure is observed in both molecules, and is assigned to coupling with protons in the 1, 4, 5, and 8 ring positions in quinoline, and in the 1, 4, 5, and 8 ring positions in isoquinoline. The normalized spin density at these positions is approximately equal to 0.23 in both molecules, assuming that the hyperfine coupling tensors for doublet-state π radicals are applicable to triplet-state molecules.

The phosphorescent states of quinoline and isoquinoline are interpreted to result from π—π* excitations. The decay constants of the isomers were found to be 0.80±0.02 and 0.95±0.1 sec, respectively.

Preliminary measurements on the phosphorescent state of cinnoline are consistent with the interpretation of this as an n—π* triplet state.
Thermal Diffusion Column Transport Coefficients for Mass 28 and Mass 29 Carbon Monoxide
Authors: Rutherford W. M.
Published: January 2005

Thermal diffusion column transport coefficients were measured for mass 28—mass 29 carbon monoxide in a 7.32 m long, hot-wire column. The three coefficients which characterize column performance were independently evaluated at wire temperatures of 350° and 500°C from the results of both static and flow separation experiments at various pressures. If the value of the thermal diffusion factor at 288°K for carbon monoxide is assumed to be 0.0054, good agreement is obtained between the experimental coefficients and those predicted from existing theory with shape factor integrals based on the Lennard-Jones 12–6 potential.
Spectra and Energy Levels of Er3+ in YCl3
Authors: Rakestraw J. W. , Dieke G. H.
Published: January 2005

Yttrium chloride is monoclinic with C2 point symmetry at the site of a Y3+ ion. The point symmetry is approximately octahedral. The absorption and fluorescence spectra of Er3+ in YCl3 are used to find the energy levels of Er3+. The Zeeman effect and the excitation of fluorescence are studied. Assuming a cubic field, the Stark splittings of the Z and Y groups are used to obtain the crystalline field parameters: A4〈r4〉=175. cm−1,  A6〈r6〉=10.4 cm−1.

The cubic field gives approximate agreement with the experimental data and explains the clustering of Stark components which is characteristic of rare-earth ions in YCl3. The total Stark splitting of the free ion levels of a rare-earth ion is larger in YCl3 than in LaCl3. The centers of gravity of the excited levels of Er3+ are higher in LaCl3 than in YCl3, and this shift increases with increasing wavenumber.
Unified Treatment of One- and Two-Electron Multicenter Integrals for Harmonic Oscillator Functions
Authors: Roberts P. J.
Published: January 2005

Compact formulas are derived for one- and two-electron multicenter energy integrals between an orthogonal basis of isotropic harmonic oscillator (Gaussian) functions in Cartesian coordinates. Up to four centers are considered. Overlap and kinetic energy integrals are given in closed form, but the potential energy integrals require a one-dimensional numerical quadrature. A technique due to Smirnov was used to obtain all formulas.
Spectroscopy of TaO and TaO2 in Neon and Argon Matrices at 4° and 20°K
Authors: Weltner William , McLeod Donald
Published: January 2005

The TaO and TaO2 molecules vaporizing from tantalum oxide at 2270°K have been trapped in neon and argon matrices at 4° and 20°K and studied spectroscopically in the infrared, visible, and near-ultraviolet regions. TaO spectra exhibit the three electronic transitions observed in the gas and analyzed by Premaswarup and Barrow. The matrix spectra lead to a probable revision of the 4155 Å gas transition, indicating that TaO has a 2Δr ground state. In all, 16 electronic transitions from the X Δ322 level have been distinguished by 18O substitution and most of the upper-state vibrational frequencies determined. Two electronic transitions of TaO2 in a neon matrix occur at 8607 Å (strong) and 6159 Å (weak). The bending frequency in the upper state dominates both of the band systems and indicates that the O–Ta–O angle undergoes a large change in the transitions. The infrared spectrum of TaO2 exhibits two bands, suggesting that the molecule is bent in the ground state. Vibrational frequencies in the ground state are assigned as follows: TaO, 1020 cm−1 (corroborating the gas value); TaO2, v1″=971 cm−1, v2″=?, v3″=912 cm−1. A molecular orbital scheme for each of these molecules is proposed leading to X 2Δr for TaO and X 2B1 for TaO2.
Crystal-Field and Spin—Orbit Matrix Elements for Transition Metal Ions with Cubic Symmetry
Authors: Euwema Robert N.
Published: January 2005

Matrix elements which are diagonal with respect to the cubic field are given for the crystal-field and spin—orbit Hamiltonians for the transition metal d-electron configurations. A multiplication factor, the free-ion reduced matrix element, is not included in the tables given.
Spectra of Matrix-Isolated NiF2 and NiCl2
Authors: Milligan Dolphus E. , Jacox Marilyn E. , McKinley John D.
Published: January 2005

The infrared (400–4000-cm−1) and ultraviolet (5000–2200-Å) absorption spectra of NiF2 and NiCl2 molecules isolated in an Ar matrix at 14°K have been observed. Sharp systems of absorptions near 780 cm−1 for NiF2 and 520 cm−1 for NiCl2 can be assigned to the antisymmetric stretching fundamental of the isolated molecules. Most of the vibrational splittings of the more abundant isotopic species have been resolved. Absorptions due to dimers and to other as yet uncharacterized species also appear. Evidence supports the hypothesis that NiF2 and NiCl2 are linear. No ultraviolet absorptions have been observed for NiF2, but the intense absorption previously observed for NiCl2 between 3650 and 2750 Å has been found to have extensive vibrational structure, probably contributed by the symmetric stretching mode of the upper state.
Study on the Quinquevalent Chromium Complex
Authors: Kon Hideo , Sharpless Norman E.
Published: January 2005

Accurate values of the parallel and perpendicular components of g-factor and hyperfine coupling tensor were determined for [CrOCln]—(n−3) where n=4 and 5, by the ESR line shape analysis. It was shown by a molecular orbital treatment that these magnetic parameters can be explained consistently by taking into account of an excited electronic configuration in which an electron in a filled orbital is excited to the half-filled level. An assignment of a hitherto unexplained visible absorption band was proposed on the same ground.
Molecular Vibrations of Quinones. II. Infrared Spectra (Solution and Vapor) of p-Benzoquinone and p-Benzoquinone-d4
Authors: Charney Elliot , Becker Edwin D.
Published: January 2005

Infrared spectra of quinone and quinone-d4 have been obtained for both vapor phase (4000–650 cm−1) and solution (4000–75 cm−1). The vapor spectra are analyzed in terms of the band contours expected for transitions polarized along the three axes corresponding to the principal moments of inertia.
Molecular Vibrations of Quinones. III. Preparation and Infrared Spectra (Solution and Vapor) of p-Benzoquinone-d1, p-Benzoquinone-2,5-d2, p-Benzoquinone-2,6-d2, p-Benzoquinone-18O2, and p-Benzoquinone-d4-18O2
Authors: Ziffer Herman , Charney Elliot , Becker Edwin D.
Published: January 2005

Three specifically deuterated quinones, p-benzoquinone-d1, -2,5-d2, and -2,6-d2, have been prepared by a scheme involving (1) the formation of the dibenzyl ether of the appropriate bromohydroquinone, (2) reaction of this bromoether with n-butyl lithium, (3) introduction of deuterium by solvolysis of the lithium derivative in D2O, (4) cleavage of the ether with sodium in liquid ammonia, and (5) oxidation of the specifically deuterated hydroquinone by chromic oxide in buffered acetic acid. Infrared spectra have been obtained for the three compounds both in solution (4000–75 cm−1) and in vapor phase (4000–300 cm−1). The band contours of the vapor spectra are analyzed and discussed.

In addition, p-benzoquinone-18O2 and quinone-d4-18O2 have been prepared by exchange of quinone and quinone-d4 with H218O. Solution spectra (4000–300 cm−1) are reported.
Molecular Vibrations of Quinones. V. Normal Coordinate Analysis of p-Benzoquinone and Its Isotopic Derivatives
Authors: Anno Tosinobu
Published: January 2005

The frequencies of the normal vibrations of ordinary, monodeutero-, 2,5-dideutero-, 2,6-dideutero-, and tetradeutero-p-benzoquinone as well as ordinary and tetradeutero-p-benzoquinone-18O2 have been calculated by using a quadratic potential function of the valence-force field type with all the important cross terms. For the out-of-plane vibrations, Anno and Sadô's force constants have been used. For the planar vibrations, two sets of force constants have been tried. One of the sets was obtained from the force constants in benzene, hexafluorobenzene and ethylene with proper considerations and modifications. In the second set, the diagonal and off-diagonal constants among the CC and the CO stretches have been obtained by the method of Coulson and Longuet-Higgins, the other constants being the same as in the first set. Further calculations have been tried in order to improve the results by adjusting a few of the force constants in such a way that some of the frequencies well established by experiment are reproduced by the calculation. Only the results for ordinary and tetradeutero-p-benzoquinone are given in the present paper; the results for other isotopic quinones are tabulated in Part VI of this series, in which the assignment of vibrational frequencies to modes of vibrations is discussed.
Ice Electrets
Authors: Gelin Henry , Stubbs Robert
Published: January 2005

Both heterocharged and homocharged electrets have been made from common ice at reduced temperatures. Partially charged ice samples exhibit multiple dielectric relaxation times. Discharge measurements show that the Gross theory of heterocharge is applicable to electrets of ice. The dielectric relaxation found by Auty and Cole does not explain heterocharge in ice.
Theory of Zeeman Effect for Rare-Earth Ions in Crystal Field with C3h Symmetry
Authors: Murao Tsuyoshi , Spedding F. H. , Good R. H.
Published: January 2005

Rare-earth ions in ethylsulfate crystals give rise to sharp-line optical absorption spectra. The purpose of this paper is to give a part of the theory of the Zeeman effect for these lines. Special cases considered especially are when the magnetic field is parallel or perpendicular to the c axis, when the light polarization is parallel or perpendicular to both the c axis and the magnetic field, and when the crystal is rotated about the c axis while the light polarization and magnetic-field directions are held constant. The dependence of the frequency and intensity of the lines on the crystal orientation gives a measure of certain properties of the internal crystal fields which have not been observable before.
Electron-Diffraction Study of Diborane and Deuterodiborane
Authors: Bartell L. S. , Carroll B. L.
Published: January 2005

The molecular structures of gaseous B2H6 and B2D6 were determined by the sector-microphotometer method of electron diffraction. Structural parameters and standard errors for B2H6 were rg(B–B) = 1.7750±0.0035 Å; rg(B–H)term = 1.1960+0.008, −0.006 Å; rg(B–H)bridge = 1.3393+0.002, −0.006 Å; and <BBHt = 120.5±0.9°. Corresponding parameters for B2D6 were 1.7712±0.0035 Å; 1.1980+0.006, −0.005 Å; 1.3335+0.002, −0.004 Å; and 119.3±0.9°. Root-mean-square amplitudes of vibration were also determined. Bridge hydrogen amplitudes exceeded terminal hydrogen amplitudes in conformity with an extension of Badger's rule. Hydrogen amplitudes exceeded deuterium amplitudes in accordance with the difference in reduced mass. Isotope effects on bond lengths were obscured by an unanticipated experimental flaw which influenced results by 1 or 2 parts per thousand.
Electron-Diffraction Study of Water and Heavy Water
Authors: Shibata Shuzo , Bartell L. S.
Published: January 2005

The structures of gaseous H2O and D2O were investigated using the sector-microphotometer method of electron diffraction. Structural parameters and estimated standard errors for H2O included the mean bond length rg(OH) = 0.976±0.003 Å, rms amplitude lg(OH) = 0.0666±0.003 Å, and mean HOH angle αg = 107.2°±3°. Corresponding values for D2O were 0.970±0.0025 Å, 0.564±0.002 Å, and 104.2°±3°. Results agreed with spectroscopic values to within the larger limits of error of the diffraction results. Analyses were based on the radial distribution method and on a new automatic ``smooth-background'' method. Observed atomic intensities deviated significantly at small scattering angles from intensities calculated using the conventional approximations. The resulting discrepancy led to a greater uncertainty in structural parameters than did the random experimental intensity errors. This almost universally neglected source of error is briefly discussed.
Extensions of the Variational Theory of Chemical Reactions
Authors: Woznick Benjamin J.
Published: January 2005

The variational theory of chemical reactions has been extended to provide estimates for reaction rates across surfaces parallel to the tangent of the rotational barrier and for the case of three-body recombination in the presence of a catalyst whose dominant interaction with the recombining atoms is attractive.
Spin—Rotation Interaction and Magnetic Shielding in OF2
Authors: Flygare W. H.
Published: January 2005

High-resolution microwave spectroscopy has been used to study the spin—rotation interaction of the two 19F nuclei in OF2. Several transitions were resolved from J=9 to J=26 where half-widths at half-heights of 12–15 kc/sec were obtained. The chemical shift of the 19F nucleus was also measured. The value of the magnetic shielding relative to F in CFCl3 is −249±1 ppm. The paramagnetic component of the shielding in OF2(σOF2p) is then related to the paramagnetic shielding in F2(σF2p) yielding σOF2p—σF2p=205×10−6. σF2p can be computed from the known spin—rotation constant in F2 yielding σOF2p=−569×10−6. This data is then combined with the microwave data on the spin—rotation interaction in OF2 to yield Maa=−42kc/sec, Mbb=−22 kc/sec, and Mcc=−49 kc/sec.
Diffusion of Boron in Graphite
Authors: Hennig Gerhart
Published: January 2005

The mobility of substitutional boron in single crystals of graphite has been measured by an etch-decoration method, which makes it possible to locate individual boron atoms by electron microscopy. The mobility of boron is not very sensitive to the boron concentration, for B/C values between 10−2 and 10−8. The diffusion constants measured between 1700° and 2400°C are 6320 exp(−157 000/RT) for motion parallel to the layer planes and 7.1 exp(−153 000/RT) for motion perpendicular to the layers.
Infrared-Absorption Spectra of Chloro-, Bromo-, and Iodoalkanes in the 400-to-100-cm−1 Region
Authors: McDevitt Neil T. , Rozek Adele L. , Bentley F. F. , Davidson A. D.
Published: January 2005

The infrared-absorption spectra of 18 haloalkanes have been studied and the carbon—halogen bending vibration assigned for each molecule. The effect of rotational isomerism on this vibration was determined. The low-frequency torsional modes have also been assigned. Solid-state studies contributed to the support of the assignments and made it possible to determine rotational effects.
Nuclear Magnetic Double Resonance. Transmission of Modulation Information through the Nuclear Spin—Spin Coupling
Authors: Freeman R. , Anderson W. A.
Published: January 2005

Nuclear magnetic double-resonance experiments are described in which the perturbing radio-frequency field is amplitude or frequency modulated, causing the precessing moment vector of a group of nuclear spins (S) to mutate at a low audio frequency. Through the action of the nuclear spin—spin coupling this modulation information is transmitted to a second group of nuclear spins (I) in the form of a selective modulation of the local magnetic field, which may be used to excite a magnetic resonance ``sideband'' signal. A general theory is given, covering both the present modulation transfer experiments and also the removal of residual splitting in spin decoupling experiments by modulation of the irradiating frequency. Numerical calculations to predict the frequencies and relative intensities of the observed signals have been carried out on a high-speed computer and presented in graphical form. In all the experimental measurements the S spins are 13C nuclei in their natural abundance, and the I spins are coupled protons, examined at 60 Mc/sec. Good agreement with the theoretical predictions has been obtained in a detailed study of the AX spin system of chloroform. The application of modulation transfer experiments to the indirect measurement of 13C chemical shifts has been illustrated for chloroform, acetic acid, and diethyl ether. The technique has also been used to discriminate between signals from molecules with different isotopic constitution; for example, in acetic acid all proton signals from molecules not containing 13C may be suppressed, clearly revealing the small long-range spin coupling between carboxyl 13C and the methyl protons. In more complex molecules the theoretical frequency and intensity diagrams can be built up by superposition of the diagrams for simpler systems. Often the relative signs of certain coupling constants may be inferred by inspection of the modulated double resonance spectrum—the relative signs of J(13CH), J(13CCH), and J(HH) in diethyl ether have been determined in this way.
Luminescence of Solids Excited by Surface Recombination of Atoms. V. Quantitative Dependence of Luminescence Response on Oxygen- and Nitrogen-Atom Densities
Authors: Sancier K. M.
Published: January 2005

The quantitative relationship between luminescence response and atom density was investigated for the lumophor CaO:Sb:Cl excited by surface recombination of nitrogen or oxygen atoms. Atom densities were determined by electron spin resonance employing molecular oxygen as a standard of spin density.

Luminescence response is essentially linearly proportional to nitrogen-atom density for total nitrogen pressures of 0.007 to 0.29 Torr. Luminescence response to oxygen atoms, determined at a total oxygen pressure of 0.016 Torr, is linearly proportional to oxygen-atom density when account is taken of the decreased response caused by oxygen-atom exposure. However, for certain operating conditions of the discharge, enhanced luminescence response occurred at oxygen-atom densities less than 3×1013 atom/cc; also, no significant decrease of response occurred with exposure to oxygen atoms at densities less than 0.4×1013 atom/cc. The enhanced response and the absence of a decreased response upon continued exposure are attributed to electronically excited oxygen species, probably O(1D) or O(1S). Equal densities of nitrogen and oxygen atoms produced about the same luminescence response.
Mercury-Sensitized Photolysis of Propylene Primary and Radical Reactions
Authors: Heller Carl A. , Gordon Alvin S.
Published: January 2005

A description is given of the mercury-sensitized photolysis of propylene and mixtures of propylene with H2, D2, and propylene-d6 at 26°C using 253.7 and 184.9-nm light. There are at least five primary steps: C3H6*→H+C3H5,  C3H6*→CH3+C2H3,  C3H6*→cyclopropane,  C3H6*→CH4+C2H2,  C3H6*→H2+(C3H4).The ratios of the primary reaction rates depend upon wavelength of the light and deuteration of the propylene. Addition of hydrogen atoms to the propylene double bond gives 5% n-propyl radicals.

We find no evidence of vinyl—vinyl radical combination to form butadiene. The cross-combination ratio of isopropyl and allyl radicals is 6½.