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Volume 42, Issue 2, 15 January 1965
42(1965); http://dx.doi.org/10.1063/1.1695953View Description Hide Description
Shock‐tube interferometry has been used to observe vibrational relaxation of O2 in O2+D2 mixtures. From 300° to 850°K the present shock tube and previous ultrasonic relaxation times in atmosphere seconds are given by . Above 1500°K the relaxation time of O2 is further shortened due to effects of chemical reaction or possibly to a resonant‐energy exchange with the more rapidly excited D2. Hydrogen vibrational relaxation is too rapid to be resolved, yielding for T = 1400°K. The vibrational relaxation of deuterium appears to be more complex than other diatoms studied and is not yet understood. However, it is observed that at T = 1400°K.
42(1965); http://dx.doi.org/10.1063/1.1695954View Description Hide Description
The model to which the cluster theory of conductance was applied in an earlier paper is extended to allow for nonpairwise contributions to the interactions among the ions. When the nonpairwise parts of the long‐range hydrodynamic interactions are included in the cluster theory calculation, then the electrophoretic term of the limiting law found by Debye, Hückel, and Onsager is recovered.
42(1965); http://dx.doi.org/10.1063/1.1695955View Description Hide Description
The electrophoretic term of the limiting law for conductance is evaluated using Oseen's expression for the velocity field generated in a fluid medium by the motion of an immersed ball. This expression accounts for the nonzero inertia and kinetic energy of the fluid, unlike Stokes' velocity field which is usually used in conductance theory. The electrophoretic term calculated in the framework of the Debye—Hückel conductance theory reduces to the classical result in the usual range of experimental conditions and also makes a very small contribution to the Wien effect for electric fields in the accessible range.
42(1965); http://dx.doi.org/10.1063/1.1695956View Description Hide Description
The calculation of the limiting‐law terms from the cluster theory of conductance, as presented in recent papers, is extended to solutions of mixtures of electrolytes. The more general evaluation of one of the cluster integrals required for this purpose is achieved by using some results from the theory of symmetric polynomials. The resulting relaxation term is very different in form from that of Onsager and Kim but, at least for solutions of three solute species, the two theories give the same numerical results for the ionic conductances in a variety of systems.
42(1965); http://dx.doi.org/10.1063/1.1695957View Description Hide Description
The M 4 band, one of the absorption bands of the M center, was observed free from any interfering absorption in additively colored KCl crystals. The band maximum was found to lie at 633 mμ, the half‐height width was 0.059 eV, and the oscillator strength was 0.052 that of the M 1 transition. In KBr, the M 4 band was observed near 700 mμ as a shoulder on the long‐wavelength side of the F band.
Microwave Absorption and Molecular Structure in Liquids. LX. Intramolecular Relaxation Mechanisms in Aromatic Ethers and Several Related Molecules42(1965); http://dx.doi.org/10.1063/1.1695958View Description Hide Description
The dielectric constants and losses of 11 aromatic ethers and related compounds in dilute benzene solution have been measured at wavelengths between 1.25 and 50 cm at temperatures from 20° to 60°. The substances measured are dibenzyl ether, benzyl phenyl ether, dicyclohexyl ether, 2‐nitrophenyl phenyl ether, m‐diphenoxybenzene, 4‐bromophenyl phenyl ether, 4‐biphenyl phenyl ether, phenoxathiin, thianthrene, triphenylphosphine, and triphenylchloromethane. The dielectric relaxation times calculated from these data indicate that most of the seemingly small values obtained result from combination of short, coupled, ring rotations with over‐all molecular rotation.
Comparison of the dipole moment values calculated for twenty‐three substituted phenyl ethers with the observed values gives no evidence of the large mesomeric moments seemingly necessary to make mesomeric charge shift a generally important factor in lowering the relaxation times of these molecules. The low relaxation time found for phenoxathiin probably results from combination of dipole orientation by a ``butterfly motion'' of the nonplanar molecule with orientation by over‐all molecular rotation.
42(1965); http://dx.doi.org/10.1063/1.1695959View Description Hide Description
A study of the kinetics of the thermal desorption of Sr from W has been performed in which the field electron microscope was used to identify the state of adsorbate—substrate system. The activation energy for the thermal desorption of Sr from W falls from 4.21±0.22 eV/atom at zero Sr coverage to 1.78±0.13 eV/atom at ``monolayer'' coverage. This latter value approaches the heat of sublimation of bulk Sr (1.69 eV/atom). The desorption energies found using field‐emission techniques deviate markedly from the extrapolated thermionic results of Moore and Allison near θ=0 and for θ>0.5. A linear relationship was found to exist between the activation energy for desorption and the logarithm of the pre‐exponential factor in the rate equation κ(kT/h) exp(ΔS‡/R).
42(1965); http://dx.doi.org/10.1063/1.1695960View Description Hide Description
Raman frequencies, polarizations, and infrared frequencies of nearly saturated aqueous solutions of KOH containing various amounts of GeO2 (0.5 to 6.0 mole liter−1) have been obtained at 25°C, and relative integrated Raman intensities of bands of the alkaline solutions at 529, 667, and 765 cm−1 were also obtained for various stoichiometric GeO2 molarities, C GeO2 , under conditions of nearly constant, and of varying stoichiometric KOH molarity, C KOH.
In the concentration ranges 0<C GeO2 <6M, and 10.53<C KOH<14.87M, the relative integrated Raman intensity of the 765‐cm−1 band, I 765, was observed to be nearly proportional to C GeO2 , which suggests that much of the germanium is present in one form, e.g., as H2GeO4 2—. However, marked downward deviations from proportionality observed for another intensity of H2GeO4 2—, I 667, evident in the range ∼2<C GeO2 <6M, indicate that appreciable concentrations of a second species, e.g., Ge2O5 2—, must contribute to the 765‐cm−1 band intensity to produce the observed near proportionality. The species Ge2O5 2— is also thought to give rise to another band at 529 cm−1, the intensity of which increases from very low to measurable values in the range 0<C GeO2 <6M, and the presence of more than one germanium‐containing species is given additional support by polarization data.
Raman and infrared frequencies of solidNa2GeO3 and of vitreous GeO2, and infrared frequencies of hexagonal GeO2, also obtained in this work, are included, as are viscosity and electrical conductivity data for alkaline solutions of germanium dioxide.
42(1965); http://dx.doi.org/10.1063/1.1695961View Description Hide Description
The 2+2→3−2 rotational transition in water vapor has been carefully studied by using both a simple video and a double modulation millimeter wave spectrometer. The line center remeasured is ν0 = 183 310.12±0.10 Mc/sec. Self‐broadening and foreign‐gas broadening were investigated over the pressure range of 5 to 400 μ of Hg with the following results:
These results, obtained by the double modulation spectrometer, have been compared with other line broadening studies, and for the first time linewidth calculations on asymmetric molecules appear to be valid.
42(1965); http://dx.doi.org/10.1063/1.1695962View Description Hide Description
Liquid—vapor equilibrium phase compositions for the binary system neon—argon have been determined at seven temperatures in the range 84.42°−129.93°K and at pressures up to 1050 psia. The vapor‐recirculation method of obtaining equilibrium was used in conjunction with a vapor‐pressure‐controlled cryostat, in which both liquid nitrogen and liquid argon have been used as the bath fluid. The results are presented in both tabular and graphical form, and the general behavior of the system is discussed. A comparison with some earlier data is given.
42(1965); http://dx.doi.org/10.1063/1.1695963View Description Hide Description
Magnetic susceptibility of (pyridine N‐oxide)‐copper(II) chloride, C5H5NOCuCl2, has been measured by the Faraday method from 90° to 300°K. The magnetic moment decreases rapidly with temperature; the dimeric structure proposed on the basis of magnetic behavior has been confirmed by the results of crystal structure determination. The crystals are monoclinic, P 21/b—C 2h 5, with four copper atoms in the unit cell of dimensions: a = 5.844 Å, b = 10.049 Å, c = 13.643 Å (all ±0.005 Å), γ = 104° 52′±10′. Data were collected by Weissenberg photography. The structure was determined from Patterson projections on (100) and (010) and refined by two dimensional electron density difference syntheses. The Cu–Cu internuclear distance of 3.23 Å is quite a bit larger than that observed in a number of dimeric copper systems. Another novel feature of the dimer is that it has distorted tetrahedral environment for copper in a binuclear system and consists of two distorted bisphenoids which share an edge.
42(1965); http://dx.doi.org/10.1063/1.1695964View Description Hide Description
The existence of ferroelectric behavior in the Phase III polymorph of potassium nitrate has permitted the direct recording of the rate of transition of the Phase III to the Phase II at temperatures far removed from the normal transformation temperature at atmospheric pressure. The data presented indicates that the III—II transition may be described by two first‐order processes which may each be described by a single rate constant. These rate constants as a function of temperature are given.
42(1965); http://dx.doi.org/10.1063/1.1695965View Description Hide Description
A brief account of the theory is given, and the results presented for a light‐scattering study of Wyoming sodium bentonite solutions in the absence and presence of applied electric fields.Measurements made without electric fields gave no indication of the side‐by‐side aggregates found by other workers. If it is assumed that the particles are flat disks, the data indicates a radius of 3400 Å, and a thickness of 9.4 Å. The application of alternating current fields to solutions of polar or electrically anisotropic particles results in a change in the angular scattering pattern, and moreover enables a distinction to be made between these two classes. Furthermore such fields introduce an alternating scattered intensity component of twice the frequency of the applied field. The solutions were subjected to fields up to 374 V cm−1 at frequencies up to 400 cps and were found to consist of at least two kinds of particles. Consideration of the frequency dependence of the intensity changes enabled rotary diffusion constants to be estimated, which in turn indicated the relative particle sizes of the two constituents. Measurements of the alternating intensity changes supported the results obtained from the data with the nonalternating changes, and this confirms the usefulness of detecting and measuring these components. x‐ray diffraction studies have revealed the two constituents of the bentonite to be sodium montmorillonite, gypsum, and quartz.
42(1965); http://dx.doi.org/10.1063/1.1695966View Description Hide Description
The possibility has been examined that structural symmetry may be utilized to reduce the order of matrices to be treated in the calculation of unperturbed mean‐square end‐to‐end distances of polymer chains. It is found that this is the case for a class of polymers possessing such a symmetry that when all the skeletal bonds are forced to be in the trans conformation the chemical structure is symmetric with respect to the plane involving skeletal bonds. For this class of polymers, the order of matrices is shown to be reduced from 3s to when the cis and trans states are forbidden to occur, and from 3s to (s+1) when the cis state is forbidden but the trans state is allowed. Here s is the number of rotational isomeric states of skeletal bonds. It is suggested that the method is equally effective in the calculation of higher even moments of end‐to‐end distances and optical anisotropies of polymer chains.
42(1965); http://dx.doi.org/10.1063/1.1695967View Description Hide Description
The infrared emission from nitric oxide mixed with argon was measured. The gas was shock heated to temperatures ranging from 1000° to 2500°K. At the same time the density variations in the heated sample were examined with a Mach—Zehnder interferometer. For varied concentrations of nitric oxide and the range of temperatures covered the observed relative emission intensity at vibration equilibrium is in good agreement with that calculated by using the measured density and the vibrational oscillator strengths derived from the experiments of Penner and Weber. The vibrational relaxation time of nitric oxide is less than 1 μsec, in laboratory time, over the above temperature range, and the corresponding minimum collision transition probability is approximately 10−3.
42(1965); http://dx.doi.org/10.1063/1.1695968View Description Hide Description
Quantum‐mechanical calculations of the transport cross sections Q (1)☆ and Q (2)☆ and the associated Ω(n,t)☆ integrals for a Lennard‐Jones (12, 6) potential are discussed. The computations are made for three values of the quantum parameter Λ* (=1, 2, 3), and include the effect of statistics. The quantum effects become quite important at reduced temperatures T * below about unity. The quantum corrections to the integrals are negative at moderate temperatures, but become positive at higher temperatures.
42(1965); http://dx.doi.org/10.1063/1.1695969View Description Hide Description
The transport collision integrals for the 12–6 potential have been calculated with exact quantal phase shifts. Tables of the collision integrals, accurate to 1 or 2 parts in 1000 over most of the temperature range, have been prepared for reduced temperatures kT/ε from 0.01 to 100 and for a number of values of the reduced de Broglie wavelength up to a value of 3.5 in steps of 0.5. The effects of statistics are included.
42(1965); http://dx.doi.org/10.1063/1.1695970View Description Hide Description
The photolysis of CH4–CD4 mixtures has been briefly investigated at 20.4°K using the xenon and krypton resonance lines. From the isotopic composition of the hydrogen and ethane fractions, it could be derived that, in the solid phase, methylene and methyl radicals are produced. The methylene radicals, which are formed by the process CH4 *→CH2+H2, insert into methane to form ethane.
In the argon‐sensitized radiolysis at 20.4° and 77°K, the hydrogen‐molecule elimination process predominates, indicating that neutral excited‐methane molecules are formed nearly exclusively. In the xenon‐sensitized radiolysis, however, mainly hydrogen atoms and methyl radicals are observed. In all inert gas‐sensitized radiolyses, there is a gradual decrease in the efficiency of the energy transfer with increasing dilution.
In the direct radiolysis, hydrogen atoms play a more important role than in the photolysis at 1236 Å. Radiolysis of CD4−C2H4 (1:0.01) mixtures indicated that, at 77°K, hydrogen atoms react with ethylene and propylene to form higher saturated hydrocarbons while, at 20.4°K, hydrogen atoms disappear mainly by recombination with other free radicals. From the isotopic composition of the ethylene fraction formed in the radiolysis of Ar–CH4–CD4 mixtures, it is surmised that a fraction of the methylene recombines to form ethylene.
Nonequilibrium Effects in the Kinetics of Isomerization Reactions and in the Kinetics of Dissociation and Recombination of Diatomic Molecules42(1965); http://dx.doi.org/10.1063/1.1695971View Description Hide Description
A study was made of the time evolution of a system of diatomic molecules undergoing dissociation and recombination and of a system of molecules undergoing isomerization. The starting point in each case was a master equation. The particular aims of the study were to determine the conditions under which the time evolution is describable by the appropriate phenomenological equation [Eq. (1) or (2)] and also to determine whether or not the phenomenological equations can hold under far from equilibrium conditions with forward and reverse rate constants whose ratio is not the equilibrium constant. In the isomerization it was found that the appropriate phenomenological equation [Eq. (2)] always holds after a sufficiently long time. In dissociation—recombination there exist systems in which the appropriate phenomenological equation [Eq. (1)] never holds. Certain necessary conditions involving rate constants for the elementary processes and the atom concentration must be fulfilled in order for this equation to ever hold. In both dissociation—recombination and isomerization the ratio of forward and reverse rate constants is always equal to the equilibrium constant when the phenomenological equations hold.
42(1965); http://dx.doi.org/10.1063/1.1695972View Description Hide Description
The spatial distribution of helium atomic and molecular radiation has been investigated in the negative glow of a dc discharge. The atomic radiation peaks sharply at the cathode edge of the negative glow, the molecular radiation less sharply at a greater distance from the cathode.Microwave quenching indicates that most of the atomic and all of the molecular radiation results from electron‐ion recombination processes. The decrease in atomic radiation reflects the decrease in atomic ion concentration which is controlled primarily by diffusion away from the cathode and by three‐body conversion to molecular ions. The molecular ions are lost by diffusion and by collisional—radiative recombination to the neutral molecule, with collisional processes predominating. The negative glow can be characterized as a plasma steady in time but with a one‐dimensional spatial decay away from the cathode.