Index of content:
Volume 31, Issue 5, 01 November 1959
31(1959); http://dx.doi.org/10.1063/1.1730564View Description Hide Description
Vinyl chloride‐d 3 has been prepared and the infrared spectrum has been obtained in the region from 400 to 4000 cm‐1. The spectrum is compared with the that of vinyl chloride. Normal coordinate analyses are made for vinyl chloride and vinyl chloride‐d 3. A force field of the Urey‐Bradley type is used for the planar vibrations, and a modified valence‐type potential function is applied to the nonplanar motions. The vibrational secular equations are set up in the GF matrix fashion. The force constants are determined by a least‐square process. The force constants established for vinyl chloride are used to calculate the fundamental frequencies of vinyl chloride‐d 3. Satisfactory results are obtained.
31(1959); http://dx.doi.org/10.1063/1.1730565View Description Hide Description
The spectra of phenol‐d and p‐nitrophenol‐d associated with amines in chloroform show, in the region of the stretching fundamental, a band splitting that can be interpreted in terms of a double minimum potential for the proton. For p‐nitrophenol and a base as strong as triethylamine, both the infrared and visible spectra show that the associated complex consists of a tautomeric equilibrium between proton transferred and nonproton transferred species. For these systems also, the potential experienced by the proton shows a double minimum. It appears, therefore, that for hydrogen‐bonded systems of the type dealt with here in nondissociating solvents the hydrogen‐bonding proton will experience a double minimum potential for all strengths of association.
31(1959); http://dx.doi.org/10.1063/1.1730566View Description Hide Description
We have derived, by using simple considerations, a relation between the diffusion constant D in a liquid of hard spheres and the ``free volume'' vf . This derivation is based on the concept that statistical redistribution of the free volume occasionally opens up voids large enough for diffusive displacement. The relation is , where v * is the minimum required volume of the void and A and γ are constants. This equation is of the same form as Doolittle's [J. Appl. Phys. 22, 1471 (1951)] empirical relation between the fluidity φ of simple hydrocarbons and their free volume. It has been shown [Williams, Landel, and Ferry, J. Am. Chem. Soc. 77, 3701 (1955)] that the Doolittle equation also can be adapted to describe the abrupt decrease in molecular kinetic constants with decreasing temperature that accompanies the glass transition in certain liquids. Our result predicts that even the simplest liquids would go through this glass transition if sufficiently undercooled and crystallization did not occur. The problem of transport in actual simple and network liquids also is discussed.
It is shown that data on self‐diffusion in some simple van der Waals liquids and liquid metals are described satisfactorily by our relation with v * near the molecular volume for the van der Waals liquids and near the volume of the ion, corresponding to the highest valence state, for the metals.
31(1959); http://dx.doi.org/10.1063/1.1730567View Description Hide Description
The previous theory treating the analogous problem is developed to include rigorously the interactions between the atomic groups whose relative spatial configurations are determined by the rotational angles of two neighboring skeletal bonds. The mean‐square end‐to‐end distances and/or the electric moments are calculated for isotactic‐ and syndyotactic‐vinylic macromolecules as well as a few other macromolecules with similar structures. As a model for linear macromolecules is adopted, the discrete one whose each C–C bond is assumed to take only three rotational configurations (e.g., trans, gauche, and another gauche). In such a model the problem of taking all of the interactions between neighboring bonds into account is equivalent to that of a one‐dimensional cooperative system. While the partition function of this system can be obtained easily, some techniques are required to find the mean quantities under consideration. Results obtained involve the task of evaluating the trace of a certain matrix of nine degrees. Numerical calculations by a computer and discussions of the results will be given in part II of this series.
31(1959); http://dx.doi.org/10.1063/1.1730568View Description Hide Description
The dielectric constant, and the ferroelectric,pyroelectric, and piezoelectricproperties of thiourea crystals have been measured in the temperature range 90°K to 300°K. At least three dielectric anomalies are found at 169°K, 177°K, and 202°K, the lowest of these corresponding to a pronounced discontinuity. The crystals are ferroelectric in two regions, below 169°K and between 176°K and 180°K. Substitution of deuterium for hydrogen causes the anomalies to move upwards in temperature by 16°, 16°, and 11°, respectively. The crystal structure has been determined in detail at 120°K in the lower ferroelectric region. The transition from the antiferroelectric room temperaturestructure to the ferroelectric state is accomplished by small rotations of the molecules such that two of the molecules in the crystal unit cell have tilts to the ferroelectricb axis appreciably different from the other two, and the resultant of the molecular dipoles along  is no longer zero. The ferroelectric reversal is thus easily accomplished by interchanging the tilts of the two pairs of molecules.
Theoretical Investigations on the Light Scattering of Colloidal Spheres. VII. Dissymmetry in Unpolarized and Polarized Light31(1959); http://dx.doi.org/10.1063/1.1730569View Description Hide Description
Light scattering of nonabsorbing colloidal spheres is calculated, on the basis of the Mie theory, for the angles of observation, γ, of 45° and 135°. The parameters considered are α = 0.2 (0.2) 15.2 and m = 1.20. The scattering ratio is derived for both angles, for both unpolarized and linearly polarized light. Numerical data are given for the dissymmetry in both unpolarized and polarized light. A graph is included for an easy, approximate calculation of dissymmetries at any m values within the range 1.00–1.25. The maxima and minima of light scattered at 45° and 135° and of the dissymmetry are discussed, and a simple equation is given for deriving the α values at which they occur if m→1.0. The results are compared with alternate ones derived from the Rayleigh‐Gans and Debye equations.
31(1959); http://dx.doi.org/10.1063/1.1730570View Description Hide Description
A method of making measurements of atomic recombination times with the use of a paramagnetic‐resonance spectrometer and its advantages are described. The theory of the paramagnetic‐resonance spectrometer applied to these measurements is presented. Methods for using both diffusion and flow systems for determining surface and volume recombination coefficients are analyzed. The operation of the system that was used is illustrated for atomic oxygen recombination. The surface recombination coefficient for oxygen atoms on a quartzsurface is shown to be 3.2×10—4 per collision, and the second‐order volume recombination coefficient was less accurately determined as 5×1015 cm6 mole—2 sec—1. The measurement of the diffusion coefficient of atomic oxygen is described. The possible application of these methods to further study of reaction rates is discussed.
31(1959); http://dx.doi.org/10.1063/1.1730571View Description Hide Description
A method has been developed for the calculation of the equilibrium properties of an ionized gas consisting of many nuclear and molecular species. An essential feature of the present calculation is that it explicitly considers more than one ionic species per atom and therefore applies to partially ionized atoms and molecules. Free and bound electrons are distinguished by counting as bound electrons all those in the ground state of each ionic species. Molecular species with internal degrees of freedom are also included. The additivity of kinetic and potential energy is assumed, a classical electrostatic potential of interaction is used, and electron degeneracy is included only in the kinetic energy terms. The Helmholtz free energy of the system is minimized with respect to the concentration of each species assumed present, thus determining the equilibrium composition of the system as a function of temperature and volume. The thermodynamic quantities of interest are then calculated for an appropriate temperature‐volume grid. This method thus allows the effect of the variation of composition on the equation of state to be determined, as well as the delineation of regions in PVT space where the electron degeneracy and electrostatic interaction each becomes important. The present model is applied to a system of particles arising from the hydrogen molecule.
31(1959); http://dx.doi.org/10.1063/1.1730572View Description Hide Description
Luminescence induced by Co60‐gamma excitation of some organic solvent‐solute pairs has been compared with 2537 A excitation as to dependence of intensity on solute concentration and on concentration of an added quencher. The solutions studied were 1,6‐diphenylhexatriene in benzene, p‐terphenyl in benzene, and p‐terphenyl in toluene. The quencher was bromobenzene. The energy‐transfer parameter Q of the Kallmann‐Furst theory and the quenching constant were obtained for each of the systems. Within an estimated experimental error of about 5%, Q was unaffected by change in source of excitation. The efficiency of quenching was found to be greater for Co60‐gamma than for uv excitation for the two systems involving p‐terphenyl. With diphenylhexatriene as solute, however, the quenching constant was unchanged. These results argue against a mechanism of energy exchange involving charge transfer. The high rates of transfer and quenching are consistent with a picture of the solvent involving the existence of small ordered regions within which exciton transfer can occur so that the entire region is viable to attack by a foreign molecule with resultant quenching or energy transfer.
Computation of Asymmetric Rotator Constants from Energy Moments. III. First‐Order Centrifugal Stretching Effects31(1959); http://dx.doi.org/10.1063/1.1730573View Description Hide Description
Further expressions are developed which relate the parameters of the asymmetric rotator to experimental data through moments of the energy levels. The expressions developed here apply to an asymmetric rotator system described by a Hamiltonian which includes terms allowing for first‐order centrifugal stretching effects. A criterion for the applicability of the first‐order theory is given.
31(1959); http://dx.doi.org/10.1063/1.1730574View Description Hide Description
The compounds have been prepared where X is F‐, Cl‐, Br‐, CH3CO2 ‐, CrO4 2‐, WO4 2‐, C2O4 2‐, HCO3 ‐, HPO4 2‐, and y is approximately 32. They form an isomorphous crystal series which is tetragonal with a=23.65±0.15 A, c=12.40±0.15 A.
A similar series of the type has been prepared where X is F‐, Cl‐, CrO4 2‐, WO4 2‐, and y′ is approximately 40. They also form an isomorphous group which is orthorhombic with a=12.10±0.10 A, b=21.50±0.15 A, c=12.65±0.15 A.
These compounds are believed to be of the clathrate type, similar in general character to the gas hydrates.
31(1959); http://dx.doi.org/10.1063/1.1730575View Description Hide Description
The spin‐coupling problem is discussed for systems of p+q nuclei falling into two groups ApBq where all members of a group are magnetically equivalent. The energies are given explicitly for p=1, arbitrary q, and formulas are given from which the transition intensities can be computed for this case. The results are applied to the proton resonance spectrum of isobutane (p=1, q=9), with the results δCH3 —δCH=0.85 ppm, A CH–CH3 =6.8 cps.
31(1959); http://dx.doi.org/10.1063/1.1730576View Description Hide Description
Samarium shows anomalies in its heat capacity near 13°K and at 105.8°K. The former has already been shown to be magnetic in origin; it appears certain that the latter is also, although there is only a slight sign of an anomaly in the magnetic data near 105°. The magnetic ordering does not appear to be explicable on the assumption of an isotropic S·S coupling mechanism. The thermodynamic functions are tabulated for the temperature region studied.
31(1959); http://dx.doi.org/10.1063/1.1730577View Description Hide Description
Line shape and f value in the ultraviolet transition 2Σ+—2Π of OH have been studied by the curve of growth method, and rough direct measurements of line width have been made. The lines Q 16, P 16, R 16, Q 216, and S 16 fit a curve of growth indicating a collision broadening width of 0.02±0.02 cm‐1 at 2600°K and 1 atmos in flame gases of the approximate composition O2 60%, H2O 20%, and CO2 20%. For the Q 16 line, the f value is (11.7±4)×10‐4. This corresponds to a radiative lifetime for the free molecule of 5.5×10‐7 sec, in excellent agreement with the earlier work of Oldenberg.
Brief discussions are given of theoretical limitations on the use of the curve of growth, and of the qualitative factors to be considered in explaining the observed line width.
31(1959); http://dx.doi.org/10.1063/1.1730578View Description Hide Description
Polarizabilities and antishielding factors are obtained for a number of ions that have ten and eighteen closed shell electron configurations. Certain empirical relationships are found so that other polarizabilities and antishielding factors can be deduced. The results using Hartree and Hartree Fock wave functions are also compared.
31(1959); http://dx.doi.org/10.1063/1.1730579View Description Hide Description
The growth of aluminum oxide crystals has been observed in progress at 80X magnification with a stereo‐microscope. Hydrogen is passed over an aluminum‐oxide rod heated by a surrounding tungsten coil. As the hot products diffuse to the cooler region around the reaction zone, the reaction reverses to grow aluminum‐oxide crystals. This system is of particular interest since it allows the screw dislocation theory of crystal growth to be examined in great detail on a high‐temperature system.
31(1959); http://dx.doi.org/10.1063/1.1730580View Description Hide Description
Liquid dispersion data in the neighborhood of the 14μ absorption bands of CCl4 and the 9μ band of CH2I2 have been analyzed in terms of the Kramer dispersion equation. The so‐called oscillator strengths obtained from the dispersion data were found to be in good agreement with those obtained directly from integrated absorption coefficients.
The liquid state absorption coefficients for the 9μ band of CH2I2 are essentially equal to that previously reported for the vapor state. Thus it would appear that the Polo‐Wilson ratio of intensities is not satisfied in this case.
31(1959); http://dx.doi.org/10.1063/1.1730581View Description Hide Description
The electrical conductivity of magnesium oxide at temperatures in the region of 1300°C is observed to depend upon the partial pressure of oxygen surrounding the sample. The conductivity increases at oxygen pressures both higher and lower than 10—5 atmospheres. At this pressure the conductivity is a minimum. This effect is increased as the iron content is increased and is almost absent in the purest samples.
The conductivity is electronic rather than ionic and the number of charge carriers is controlled by the number of lattice vacancies. The dependence of conductivity on oxygen pressure may be satisfactorily explained by changes in stoichiometry and thus lattice defects in magnesium oxide. These changes in stoichiometry are larger when the magnesium oxide is contaminated with a variable valence impurity like iron than when it is pure.
If an explanation based on iron changing valance state is accepted, then it may be demonstrated by an analysis of the chemical equilibria involved that anion deficiencies must appear at low oxygen pressures, cation deficiences at high oxygen pressures, and that all defects must lie close to the variable valence impurity ions.
31(1959); http://dx.doi.org/10.1063/1.1730582View Description Hide Description
Observations of the Stark effect in the microwave rotational spectra of light molecules have been extended into the sub‐millimeter wave region. The Stark shifts of the J=0→1 transition of deuterium chloride at 0.93 mm wavelength, and of deuterium bromide at 1.18 mm have been measured. Values of the molecular electric dipole moment μ, obtained from analysis of the data, are found to be 1.12±0.04 debye for DCl and 0.83±0.02 debye for DBr. An error in the calculation of μ for DI, from measurements at 1.5 mm previously reported, is corrected, and μ for DI is found to be 0.445±0.02 debye.
31(1959); http://dx.doi.org/10.1063/1.1730583View Description Hide Description
BaTiO3 has been activated with Pr, Sm, Eu, Dy, or Er ions. The fluorescence spectra were determined at —196°C, —28°C, room temperature, and at 130°C. We looked for crystalline field effects on the energy levels of the rare earths and changes in these effects as the crystallographic phase of BaTiO3 is changed. In particular, we sought changes at the Curie point in going from the ferroelectric tetragonal phase to the cubic phase. The high‐temperature data were largely unresolvable and no changes were observed at the low‐temperature transitions in going from the tetragonal to the orthorhombic phase in the range of 5 to 13°C and from the orthorhombic to the rhombohedral phase in the range of —70 to —80°C. No crystal field splittings were observed at any temperature, leading to the possible conclusion that the rare earth centers are in positions of either high symmetry or low field strength. The fluorescence data support the hypothesis that the rare earths are present as the trivalent ions and that they can be assigned energy levels and term signatures resulting from the 4fn configuration.