bluuebunny/crossref_metadata_2025 huggingface dataset:
Intramolecular Energy Relaxation. Butyl Radical Decomposition at High Pressure
Authors: Placzek D. W. , Rabinovitch B. S. , Dorer F. H.
Published: January 2005

A study of the gas-phase decomposition of chemically activated 2-butyl radicals, produced by addition of H atoms to cis-butene−2, has been made over a wide range of pressures at 304°K. Together with earlier work below 5 mm at 300°K, the study of this reaction now embraces the range 1.6×10−3 mm to 115 atm. The observed rate constant for decomposition, ka, is invariant within experimental error over the range 0.036–115 atm and equals 1.62×107 sec−1; at the highest pressure of hydrogen bath molecules, the collisional relaxation time is τcoll∼3×10−13 sec. The assumption of randomization of internal energy, common to the RRK and RRKM theories of unimolecular reactions, is strongly validated by the present results for complex molecules on a time scale of >10−13 sec. Reasons are discussed why the assumption may hold for small molecules also. It appears that the RRKM treatment may be applied as a working theory to polyatomic molecules under virtually all experimental conditions that might be encountered for ground electronic-state species.
Electronic Structure of C2
Authors: Fougere P. F. , Nesbet R. K.
Published: January 2005

The electronic structure of the C2 molecule has been studied over the range R = 1.5a0 to 8.0a0 using three different Slater-type-orbital basis sets and two different levels of configuration interaction. Analytic potential curves and computed spectroscopic constants are given for all states studied. The behavior of all eigenvalues of each CI matrix was studied extensively with excellent agreement between molecular results and those obtained by independent calculations on a pair of separated carbon atoms. The Wigner—Witmer rules were obeyed in every case.

Observed and computed spectroscopic constants were highly correlated statistically; linear relationships were determined which allow semiempirical prediction of spectroscopic constants for those states not yet observed. Using the predictions for Te, an electronic spectrum has been derived.
Proton Tunneling in the Hydrogen-Evolution Reaction
Authors: Bockris J. O'M. , Matthews Dennis B.
Published: January 2005

The quantum-mechanical theory of tunneling was applied to the proton-discharge step of the hydrogen-evolution reaction. An unsymmetric Eckart barrier with allowance for zero-point energies was employed. The quantum-mechanical rate iq was calculated by integration with a digital computer for a large number of combinations of barrier width, barrier heights, heats of reaction, and temperatures over a large potential range for protium, deuterium, and tritium. From these results the quantum-mechanical transmission coefficient τ and the quantum-mechanical correction Γ to the separation factor, Tafel slopes, and activation energies were calculated. By comparison to observed values of SH,T, and SH,T as a function of temperature and potential the most probable barrier parameters were obtained. These values were tested by comparison of calculated and observed activation energy, Tafel slopes, SH,D as a function of potential, and the rate of protium evolution at high cathodic overpotentials as a function of temperature. The degree of proton tunneling was found to be significant being 69% at a cathodic overpotential of 1 V for Hg in acid solution.
Consistent Fourth Virial Coefficient for a Square-Well Potential Gas
Authors: Cole G. H. A.
Published: January 2005

The fourth virial coefficient D is derived for a classical gas composed of particles interacting according to the square-well potential having the form ψ(r) = ∞ for r<1, ψ(r)=—ε for 1<r<2, and ψ(r)=0 for r>2, where ε is the magnitude of the attractive well depth and the hard-core diameter is the unit of distance. The calculations are based on the Born—Green—Yvon equation and the density modified form of the original Kirkwood superposition approximation expression, viz., g(3)(r, s, t) = g(2)(r)g(2)(s)g(2)(t)[1+X1n], where g(2) and g(3) are, respectively, the pair and triplet distributions, n is the average particle number density, and (r, s, t) are the triplet particle-separation distances. The approximation is invoked that X1 is a function of the gas temperature T and of ψ, but is independent of (r, s, t). X1 is chosen in order to ensure consistency between the values of D calculated independently from fluctuation theory and from the virial theorem. The expression derived for X1 in this way is Eq. (21) of the text. Consistent values of D are then to be determined from Eq. (22). Data for D are calculated as function of T according to the present arguments and a comparison is made in the form of a graph with alternative calculated data.
Study of the Low-Frequency OH− Motions of LiOH by Neutron Inelastic Scattering
Authors: Safford George J. , LoSacco Frank J.
Published: January 2005

Low-frequency OH− motions in polycrystalline LiOH have been studied in the range 900 to 8 cm−1 by inelastic neutron scattering at temperatures of 220°, 293°, 360°, and 412°K. This experiment contrasts the models proposed by Hexter and Wickersheim to explain the infrared sideband splitting in LiOH. The experimental data show the following: (1) The infrared sidebands of 152 and 135 cm−1 must be associated with an acoustic mode with a cutoff near 138 cm−1; (2) the sideband of 95 cm−1 may be associated with a possible acoustic mode with a cutoff in the range 85 to 100 cm−1; (3) optical modes are observed at 625, 468, and 332 cm−1; (4) an exact description of the OH− motions associated with each mode is not yet available. Further, the present data are difficult to correlate with a highly localized rotational model.
Energy Levels of Pu3+ in Lanthanum Trichloride
Authors: Conway John G. , Rajnak K.
Published: January 2005

Polarized absorbtion spectra and some Zeeman effect measurements in the region of 20 000–32 000 cm−1 are reported for Pu3+ in LaCl3. A total of 25 J levels was fitted with an rms deviation of 100 cm−1 with the parameters values E0=14 930.5, E1=3726.7, E2=14.99, E3=350.18, ξ=2260.2, α=36.5, β=−1171. The large values of α and β indicate that configuration-interaction effects cannot be neglected in an analysis of the spectra of the higher actinides.
Spectroscopic Study of the Reduction of Nickel and Cobalt Ions in Sapphire
Authors: Müller Rudolf , Günthard Hs. H.
Published: January 2005

It is shown that Ni3+ and Co3+ in sapphire single crystals may be reduced to Ni2+ and Co2+ by hydrogen or deuterium gas at high temperatures. The ions may be reoxidized by heating the crystals in oxygen. From studies of the ir spectra the hydrogen is shown to form hydrogen-bonded groups of the type O–H···O situated near the site of the reduced heavy-metal ion. The assignment of the visible and the uv spectra for the reduced species Ni2+ and Co2+ in the trigonal crystal field of sapphire is suggested, which also allows some corrections of the trivalent spectra. Crystal-field parameters for the divalent species obtained by second-order perturbation theory and by trial-and-error adjustment, are as follows: Ni2+:  Δ=10 700 cm−1,B=970 cm−1,C/B=4.7,v<0Co2+:  Δ=12 300 cm−1,B=915 cm−1,C/B=4.6,v>0
Scintillations and Energy Transfer in Argon—Nitrogen Mixtures
Authors: Schultz Harvey A.
Published: January 2005

Pulse-height measurements have been made on scintillations produced by the complete stopping of alpha particles in gaseous argon, nitrogen, and argon—nitrogen mixtures. The results are correlated with the published results of spectrographic studies to derive information about energy transfer in collisions among Ar and N2 molecules.

The optical system responds to light within the spectral range 2200–6000 Å. Total pressures varied from 3.5 to 6 atm. It was observed that the pulse height is greatest for pure argon. As nitrogen is added, the pulse height decreases, then increases, and finally decreases again. From this behavior and the effect of total pressure, it is concluded that the detectable light consists of three components: (1) that emitted by argon excited directly; (2) that emitted by a nitrogen state, probably C 3Πu, excited by energy transfer from an argon state that does not emit in the detection range, apparently the lower metastable state, (3) that emitted by nitrogen excited directly. The states that emit Components (1) and (2) are quenched by nitrogen in the ground state. For three pairs of competing processes, one pair associated with (1) and two with (2), values of the product (lifetime)×(cross section)×(relative velocity) have been obtained by fitting kinetic equations to the pulse-height data. The breakdown of the products into individual factors is discussed.
Absolute Gross Ionization Cross Sections for Electrons (0.6–12 keV) in Hydrocarbons
Authors: Schram B. L. , van der Wiel M. J. , de Heer F. J. , Moustafa H. R.
Published: January 2005

Measurements have been made of absolute gross ionization cross sections for 0.6–12 keV electrons in the following hydrocarbons: the series of alkanes from methane to hexane, a number of alkenes, butadiene, and benzene. A description of the experimental technique is given, the results are compared with those of other authors and the additivity of the cross sections is discussed.

In all cases the energy dependence of the cross sections is in agreement with the theoretical relation: the cross section σ is proportional to MI2Ee1−1 lnEe1, which gives a possibility of comparing with photoionization cross sections.
Symmetry Rules for Optical Rotation
Authors: Schellman John A.
Published: January 2005

It is shown that to produce optical rotation in a chromophore, a potential function must have the symmetry properties of a pseudoscalar in the symmetry group of the unperturbed chromophore. It is thus possible to establish regional rules of optical rotation without recourse to particular models and assumptions of the electronic states of the chromophore. Formulas and geometric representations of the resulting regional rules are given for a number of symmetries which are encountered in molecular problems. The results are not applicable to coupled oscillator models of optical rotation.
Thermal Relaxation Absorption of Sound in the Deuterated Methanes at 26°C
Authors: Gravitt James C. , Whetstone Clayton N. , Lagemann Robert T.
Published: January 2005

The thermal relaxation absorption in the deuterated methanes has been obtained by the tube method for frequencies between 20 and 640 kc/sec·atm. The relaxation time, transition probability, and collision efficiency were determined for each gas. The collision efficiency as a function of molecular weight has been found to follow a simple relation of the form: P10∝[M]−½.
Non-Gaussian Corrections to Van Hove's Gs(r, t) for a Monatomic Gas
Authors: Desai Rashmi C.
Published: January 2005

Non-Gaussian corrections to Van Hove's self-correlation function, Gs(r, t), are studied for real monatomic gases. Gs(r, t) is identified with the motion of a tagged atom in a dilute gas, where the motion is determined entirely by free streaming and random binary collisions with the untagged atoms. In this description, Gs(r, t) is the velocity integral of a distribution function f(r, v, t) which is initially Maxwellian, localized at the origin, and which satisfies a linearized Boltzmann equation. Spatial moments of Gs(r, t) are calculated using the Lennard-Jones (12–6) potential and the modified Buckingham exp (14–6) potential as interatomic potentials. Results are compared with those using a rigid-sphere potential and with those of Rahman from a high-density molecular-dynamics calculation. It is found that (i) the behavior of non-Gaussian corrections is qualitatively similar in all the cases, (ii) the corrections are larger for higher densities, and (iii) at low densities, the corrections increase almost by a factor of 2 when attractive forces are included.

It is also shown that the moments approach (through space-dependent BE) and the velocity correlation-function approach (through velocity—space BE) in calculating the non-Gaussian corrections are equivalent.
NMR Studies of the Pressure Dependence of Self-Diffusion in Four Organic Solids
Authors: Anderson J. E. , Slichter W. P.
Published: January 2005

NMR pulse techniques have been used to study the influence of hydrostatic pressure on self-diffusion in four organic solids composed of nearly spherical molecules: cyclohexane, 2,2-dichloropropane, t-butyl chloride, and t-butyl bromide. The self-diffusion was studied from the pressure and temperature dependence of T2, the spin—spin relaxation time, at pressures between 1 and 680 atm, and at temperatures within 10–50 deg of the melting point. The measured activation volumes were 8%—15% of the molar volumes. Comparable ratios have been previously observed for rotational motion in similar solids. The activation enthalpies for self-diffusion were 5–6 kcal/mole, somewhat exceeding the values for rotational motion. Comparisons are made with the latent volumes and enthalpies of fusion.
Mass-Spectral Studies of Kinetics behind Shock Waves. III. Thermal Dissociation of Fluorine
Authors: Diesen R. W.
Published: January 2005

The thermal dissociation of molecular fluorine in an inert gas was investigated over the temperature range 1650°—2700°K in a shock tube coupled to a time-of-flight mass spectrometer. Rate constants were determined from both fluorine molecule and atom analysis in mixtures containing 1% F2 or less. The results are compared with the results for other diatomic molecules and the variations discussed.

A simple correlation between the orifice flow parameters and the experimental spectra is presented along with some information concerning the rather elusive boundary layer.
Xenon-Sensitized Radiolysis of Propane
Authors: Bone L. I. , Sieck L. W. , Futrell J. H.
Published: January 2005

The xenon-sensitized radiolysis of propane has been investigated in the presence and absence of small amounts of ion and free radical interceptors. From an analysis of mixtures of deuterated propanes and a knowledge of radical disproportionation yields in the scavenged and unscavenged systems it is possible to construct a complete quantitative kinetic analysis for the decomposition. Ion titration methods demonstrate that the neutralization of C3H7+ ions occurs heterogeneously in the system investigated and leads quantitatively to the production of equivalent yields of isopropyl radicals and hydrogen atoms.
Fundamental Frequency Assignment of Thionyl Fluoride (SOF2)
Authors: Pace E. L. , Samuelson H. V.
Published: January 2005

The fundamental frequency assignment of thionyl fluoride has been made from Raman spectra of the liquid at −100°C and the gas at 2.5 atm and the infrared spectrum of the gas. The sample used has a purity of greater than 99.9 mole %. The fundamental frequency assignment with the following frequency values taken from the infrared spectrum is ν1(a′), 1329.9, 1339.3 cm−1 (Fermi resonance doublet); ν2(a′), 808.2 cm−1; ν3(a′), 530.4 cm−1; ν4(a′), 377.8 cm−1; ν5(a′), 747.0 cm−1; ν6(a″), 392.5 cm−1.

The symmetric and asymmetric SF2 bending modes, ν4 and ν6, have been definitely identified in all the spectra and their symmetry characterized by polarization measurements from the Raman spectrum of the liquid.
On the Non-Hecht Pulse-Height—Voltage Behavior of Anthracene
Authors: Sage Gloria W.
Published: January 2005

The existence of a p—n junction is shown to be able to account for non-Hecht pulse-height-vs-voltage curves in pulsed photoconductivity measurements. No changes in the pulse-height-vs-voltage curves were observed in crystalline anthracene, however, when capacitive feedback was used to eliminate the effect of such a junction.
Electrical Conduction by Oxygen Ions in Cerium Oxide
Authors: Holverson E. L. , Kevane C. J.
Published: January 2005

Oxygen gas was observed by means of a mass spectrometer to be evolved from calcium-doped ceramic cerium oxide when direct current was passed through it at 450°C. The applied voltage necessary to cause the electrolysis was about 100 V across a sample 4 mm long containing 0.86 at. % calcium. When voltages of 1.0 V or less were applied to ceramic and single-crystal samples there were pronounced transients and nonlinear potential distributions. These latter effects appear to be consistent with a picture of oxygen ions migrating to an electrode where they are at least partially blocked.
Melting of Iodine at High Pressures
Authors: Klement William , Cohen Lewis H. , Kennedy George C.
Published: January 2005

The melting curve of iodine, which has been determined by differential thermal analysis, monotonically increases from about 114°C at zero pressure to about 590°C near 30 kbar. The extrapolated zero-pressure slope for the melting curve is consistent with the value of 27.2 deg/kbar, as calculated from zero-pressure data for the volume and entropy changes, and with the 27.8-deg/kbar value from the unpublished data of Babb; near 30 kbar, the slope is about 11 deg/kbar. To a good approximation, the melting characteristics of the isostructural elements—iodine, bromine, and chlorine— should be quite similar, and the data for these other halogens are examined in an effort to anticipate their behavior at high pressure.
Raman Spectral Studies of the Effects of Urea and Sucrose on Water Structure
Authors: Walrafen G. E.
Published: January 2005

Integrated intensities of the 152–175-cm−1 intermolecular Raman bands from water and ∼2M aqueous solutions of urea and sucrose were obtained. The intensity data and the stoichiometric water molarities of the solutions were then employed in conjunction with an operational definition to obtain information related to ``structure-breaking'' and ``structure-making'' effects. Urea and sucrose were thus found to produce effects on the water structure in general agreement with the work of Klotz and of Frank.
Host-Crystal Effects on the Mechanism of the π, π Phosphorescence. II. N-Heterocyclics
Authors: Chaudhuri N. K. , El-Sayed M. A.
Published: January 2005

The polarization of the π, π* phosphorescence emission of quinoxaline (1,4-diazanaphthalene) dissolved in EPA rigid glass as well as in durene host crystal has been measured and the two compared. The polarization characteristics of the different vibronic bands in the two hosts indicate that the emission originates from at least two mechanisms—a first-order mechanism that gives rise to Subspectrum I with the 0, 0 band as its origin, and a second-order, spin—orbit—vibronic mechanism that gives rise to Subspectrum II. When the host is changed from EPA to durene, the polarization of Subspectrum I in the quinoxaline framework seems to change from out of plane to long axis. Subspectrum II seems to be less sensitive to host-crystal effects than Subspectrum I. The similarity of these results to those obtained previously for naphthalene-d8 (Chaudhuri and El-Sayed) might indicate that the lone pair on the nitrogens in quinoxaline plays no specific role in explaining this phenomenon. This conclusion suggests that the most probable configuration for quinoxaline in durene is that in which the lone pairs on the nitrogen atoms of quinoxaline are far away from the methyl groups of durene. The observed durene host-crystal effects on the emission of quinoxaline can be explained in a similar manner to those given for naphthalene. It is proposed that the quinoxaline molecule in durene crystal is slightly nonplanar in its triplet state due to repulsive forces of the methyl hydrogens of durene and the hydrogen atoms of the quinoxaline molecule. The nonplanarity results in an enhancement of the spin—orbit interaction between singlet and triplet π, π* states and thus introduces long-axis polarization. Mixing between quinoxaline triplet state and durene-crystal states is an alternative mechanism and is briefly mentioned.
Molecular Orbital Studies of the Ground and Low-Lying Excited States of the HeH+ Molecular Ion
Authors: Michels H. H.
Published: January 2005

The molecular ion HeH+ has been examined using a method of molecular orbital calculation in which the total wavefunction is taken as a linear combination of configurations, each a properly antisymmetrized product of flexible, elliptic functions. We have examined the ground 1Σ state and 14 excited states of 1Σ, 3Σ, 1Π, and 3Π symmetry. Including the ground state, there are a total of seven bound molecular states for this system, all arising from atomic states with principal quantum number of 2 or less. All higher molecular states are indicated to be repulsive. Contrary to previous investigations, we find that the first excited 1Σ state is weakly bound and can support several vibrational levels. An extensive analysis of the final optimized wavefunctions has been made and, in addition to the potential curves, we have evaluated spectroscopic constants, values of the radiative transition moments, and certain other molecular quantities. An analysis of experimental studies which require a detailed knowledge of the electronic properties of this molecular ion is given.
Negative Fragment Ions from Resonance Capture Processes
Authors: Dorman F. H.
Published: January 2005

An examination of negative fragment ions formed by resonance capture processes has been made using a mass spectrometer. It has been found in some cases that the various fragments for a particular molecule arise at the same ionizing energy, possibly by competing decomposition paths from the same state of the negative molecular ion. Other cases where the fragments do not arise at exactly the same energy may be explained by close upper energy states of the negative molecular ion.

In general the observed ionization energies are greater than those calculated from the energies of bonds broken and electron affinities. Kinetic energy measurements on some of the more abundant fragments, i.e., Cl− (CCl4, CH3·CH2Cl·CO), O− (SO2, CO2, N2O, NO), show that this excess energy is not translational.
Rotational Excitation of Molecules in Collisions with Slow Electrons
Authors: Wijnberg L.
Published: January 2005

The scattering of slow electrons on dipolar symmetrical-top molecules and on quadrupolar linear molecules is calculated at energies below the threshold for vibrational excitation. The result for symmetrical-top molecules is the same as that obtained previously for linear molecules. The result for quadrupolar linear molecules is independent of the energy of the incident electron.
Anisotropic Rotational Relaxation in Rigid Media by Polarized Photoselection
Authors: Lombardi John R. , Dafforn Geoffrey A.
Published: January 2005

A study is made of anisotropic rotational relaxation of solute molecules in rigid glasses. Assuming the relaxation process to be Brownian diffusion, equations are derived which connect the rate of depolarization in a photoselection experiment with the components of the rotational-diffusion tensor. These equations are an extension to symmetric- and asymmetric-top cases of equations previously derived only in the spherical-top limit. These new equations indicate the possibility of determining two distinct relaxation times for the molecule. In the light of these equations previous measurements are extended to allow measurement of a a second relaxation time for N,N,N′,N′-tetramethylparaphenylenediamine in various mixtures of 3-methylpentane and isopentane at 77°K. These results allow a more sensitive examination of the character of the local environment of solute molecules in such media. In particular, the predictions of Stokes' law for an ellipsoid rotating in a continuous viscous fluid are compared with the experimental results. A discrepancy of a factor of as much as 5 is found, and the implications of this are discussed.
Random Sequential Addition of Hard Spheres to a Volume
Authors: Widom B.
Published: January 2005

The configurations produced by placing spheres one at a time in a volume, subject to no overlap of the spheres but otherwise placing each at a point chosen at random, differ in a fundamental way from the configurations characteristic of a hard-sphere system of the same density which is in thermodynamic equilibrium. The difference is illustrated in four examples. The density at which the system becomes jammed is found in each case. The distribution of gaps produced by the random sequential placement of spheres on an infinite line is found for all densities up to that of jamming.
Compressibilities of the Molten Alkali Nitrates and Silver Nitrate at High Pressure
Authors: Owens B. B.
Published: January 2005

The densities of the pure molten salts LiNO3, NaNO3, KNO3, RbNO3, and AgNO3 were determined by the piston—cylinder method at pressures up to 9000 atm. The temperature covered by the measurements was from just above the liquidus curves up to about 500°C. The results were related to the corresponding-states theory of fused salts. In the case of LiNO3, deviation from the corresponding-states law was ascribed to anion—anion contact.
Optical Absorption and Energy Levels of Manganese in ZnS : Mn Crystals
Authors: Gumlich H. E. , Pfrogner R. L. , Shaffer J. C. , Williams F. E.
Published: January 2005

The energy of the 6S state of the 3d5 configuration of substitutional manganese is located with respect to the band structure of zinc sulfide by approximate theoretical methods and found to be consistent with a tight-binding, crystal-field analysis for the states of this impurity. In addition, the perturbation by the manganese of the band structure is estimated and found to be negligible. Optical absorption measurements are reported on a series of manganese-activated crystals. The five absorption bands are ascribed to intercombination transitions in the 3d5 configuration of manganese. The intensities of these bands are linear in manganese concentration. The peak absorption energies are analyzed using the Racah coefficients and the crystal field as parameters, and the most probable identification of the transitions determined. The energy of the 6S state of substitutional chromium is also estimated and found to agree with experiment, thus supporting the approximate theoretical methods used for locating these impurity states with respect to band structure.
On the Electronic Energy of a One-Electron Diatomic Molecule near the United Atom
Authors: Brown W. Byers , Steiner Erich
Published: January 2005

The behavior of the electronic energy for the ground state of a one-electron heteronuclear diatomic molecule in the vicinity of the united atom is obtained through terms of order R5 in the internuclear distance R. The presence of a term in R5logR reveals that the electronic energy is not an analytic function of R at the united atom. The expansion is checked by means of the Hellmann—Feynman theorem and the work of Dalgarno and Lynn.
Correlated EPR—Optical Spectra of Potassium in Ethylamine—Ammonia Mixtures
Authors: Dalton L. R. , Rynbrandt J. D. , Hansen E. M. , Dye J. L.
Published: January 2005

Extensive electron paramagnetic resonance (EPR) studies of potassium in ethylamine—ammonia mixtures were made over a temperature range of −180° to +100°C and at varying ammonia concentrations up to 68 mole %. Hyperfine splittings, g values, linewidths, and spin concentrations were measured. Optical spectra were measured from −65° to +35°C for a number of the solutions.

Correlation of optical and EPR results rules out the assignment of the visible absorption to the monomeric species responsible for hyperfine splitting. The unusual temperature dependence of the EPR spectra cannot be explained in the light of current models, nor can the ammonia dependence be quantitatively interpreted. A model involving equilibrium between atoms and monomers quantitatively describes the temperature dependence. To explain the dependence upon ammonia concentration, it is necessary to consider two monomeric species, one fully solvated by ethylamine and the other involving replacement of ethylamine by one molecule of ammonia.

Above about 8 mole % ammonia, computer analysis of the EPR spectra showed the building-in of an extra absorption consisting of a single broad line. The intensity of this absorption relative to the four-line pattern continued to increase until the lines merged at about 25 mole % ammonia.

Under varying conditions, the optical spectra showed the three peaks characteristic of metal—amine solutions. Relative intensities were very sensitive to temperature and ammonia concentrations. At low ammonia concentrations only the visible absorption was obtained while the intermediate and infrared absorptions occurred at higher concentrations. The latter two peaks were favored by high temperature, while the visible absorption was more pronounced at lower temperatures. These spectra are discussed in the light of current models for metal—amine solutions.
Brownian Motion of Polyatomic Molecules: The Coupling of Rotational and Translational Motions
Authors: Condiff Duane W. , Dahler John S.
Published: January 2005

The coupling of rotational and translation Brownian motions is examined from several points of view. The first is a phenomenological theory based upon generalized Langevin equations of motion and a Markoff integral equation. Next, a more detailed statistical-mechanical theory is fashioned after the pattern of Kirkwood's theory for nonequilibrium processes in monatomic liquids. Both schemes lead to a generalized Fokker—Planck—Chandrasekhar equation for the singlet-distribution function. This equation includes terms that account for separate rotational and translational motions as well as two mutually symmetric contributions which are descriptive of their coupling. The friction tensors associated with the uncoupled components of these motions are found to be proportional to the autocorrelations of the environmental force and torque which act upon a given molecule. The frictional coupling is related to the cross correlation of force and torque. From the principle of microreversibility it is possible to establish a reciprocal relationship between the two coupling tensors. A third approach is to derive the generalized Fokker—Planck equation from the Boltzmann equation for a dilute solution of rotating molecules. This has been done for the model of perfectly rough spheres and also for ``loaded spherocylinders.'' In both cases explicit formulas are obtained for the various friction tensors. The last section of the paper is devoted to the application of these theories to problems of diffusion.
Positron Annihilation in Materials under Ionizing Radiation
Authors: Tao S. J. , Green J. H.
Published: January 2005

Positron-annihilation lifetime spectra in tritiated water and ice are described, and the effect of irradiation products on positron-annihilation rates in a medium is estimated. In a liquid medium the interference mainly comes from stable products accumulated during irradiation and in a solid medium from free radicals frozen in the lattice. It is also indicated that care must be taken in preparing samples for positron-annihilation experiments to avoid excessive radiation damage to the medium by the positron source.
Nuclear Magnetic Resonance Studies of Pure and Samarium-Doped CaF2 Crystals
Authors: Lysiak R. J. , Mahendroo P. P.
Published: January 2005

The spin—lattice relaxation time T1 of 19F was measured over a temperature range of 77° to 1300°K in natural and synthetic CaF2 crystals and in CaF2 crystals doped with 0.05% Sm, 0.16% Sm, and 1.20% Sm. Most of the data was taken with the magnetic field along the [100] and [111] directions using the magnetic recovery method. For annealed samples T1 at room temperature and below is found to be inversely proportional to the concentration of samarium. Measurements show that in the high-temperature regions T1 is primarily governed by translational diffusion. Activation energies in the extrinsic and intrinsic regions were found to be 0.36 and 2.3 eV, respectively, for the pure sample and 0.53 and 2.4 eV for the doped samples. These are in good agreement with the activation energies obtained from conductivity measurements. The knee separating the extrinsic and intrinsic regions occurred at higher temperatures as the amount of dopant was increased. The T1-vs−1/T curves had a minimum at 1120°K for all the samples. Below 400°K T1 was found to be directly proportional to temperature for the doped samples. The low-temperature data indicate that the correlation time of samarium at room temperature is of the order of 10−14 sec.
Thermal Energy Ion—Neutral Reaction Rates. II. Some Reactions of Ionospheric Interest
Authors: Goldan P. D. , Schmeltekopf A. L. , Fehsenfeld F. C. , Schiff H. I. , Ferguson E. E.
Published: January 2005

A pulsed, flowing afterglow has been utilized to measure rate constants at room temperature for the following reactions involving NO: N2++NO→NO++N2,k1≈5(+1,−3)×10−10cm3/sec,N++NO→NO++N,k2=8(+1,−4)×10−10cm3/sec,O2++NO→NO++O2,k3≈8(+2,−5)×10−10cm3/sec,O++NO→NO++O,k4≤2.4×10−11cm3/sec.In addition the following related reactions have been measured:N++O2↗NO++O↘N+O2+,k5≈1(+0.1,−0.6)×10−9cm3/sec,N2++O2→O2++N2,k6≈1(+0.2,−0.6)×10−10cm3/sec,O2++N→NO++O,k7≈1.8(+0.2,−0.9)×10−10cm3/sec.Some additional information concerning the end products of N++O2 is offered.
Oxygen−17 Nuclear Magnetic Resonance Study of the Hydration Shell of Nickelous Ion
Authors: Connick Robert E. , Fiat Daniel
Published: January 2005

The solvation shell of nickelous ion in aqueous solution at room temperature was observed using 17O nuclear magnetic resonance. The hyperfine interaction A between the unpaired electrons of the nickelous ion and the 17O nucleus was found to be 3.0×107 cps. The relaxation time of the electron, assuming T1e=T2e, was found to be 4.3×10−12 sec. Calculations show that the relaxation of the 17O nucleus occurs through the scalar coupling with the unpaired electrons, whereas the relaxation of the protons occurs through the dipolar coupling. Consequently, in the latter case the calculated electron relaxation time is very sensitive to the Ni–H distance, whereas in the former it is independent of the Ni–O distance, but governed by the independently determined hyperfine coupling constant. It is also pointed out that in the expression for the dipoledipole interaction between the nuclei and the unpaired electrons it is necessary to distinguish between the longitudinal and transverse relaxation times of the electrons.

The rate constant at 298°K for the exchange of water between the hydration shell and the bulk was found to be (3.0±0.3)×104 sec−1, and the enthalpy of activation 10.8±0.5 kcal/mole.
Dielectric Studies. IX. Relaxation Processes of Anisole- and Fluorine-Substituted Anisoles
Authors: Farmer D. B. , Holt A. , Walker S.
Published: January 2005

The dielectric constants and losses at wavelengths of 0.428, 0.860, 1.249, 1.850, and 3.220 cm and the static dielectric constant at 149.9 m have been measured for methoxypentafluorobenzene, pentafluorobenzene, trifluoromethoxybenzene, and anisole in cyclohexane solutions at 25°C. Measurements were also carried out on trifluoromethoxybenzene in decalin solution at 25°C. Dielectric relaxation times have been evaluated and the results for methoxypentafluorobenzene, trifluoromethoxybenzene, and anisole have been interpreted in terms of two relaxation times, one corresponding to molecular rotation and the other to intramolecular group rotation. Consideration has been given to the shortening of the methoxy group relaxation time in the pure liquid state compared with that in dilute solution. Mesomeric moments have been estimated from the dielectric data.
Primary and Afterglow Emission from Low-Temperature Gaseous Nitrogen Excited by Fast Electrons
Authors: Sebacher Daniel I.
Published: January 2005

Measurements were made of the primary and afterglow emission decay times of some of the emitting species in an expanded nitrogen flow when excited by a 10-kV electron beam. Both the first negative system of N2+ and the second positive system of N2 were observed in the afterglow to persist for about 2×10−6 sec. The origin of the afterglow is explained by the possible transfer of energy from ground-state N2+ ions and secondary electrons to ground state N2 molecules. This is substantiated by observations of the departure from a Boltzmann distribution of the rotational energies in the N2 molecules.
Electric Quadrupole Transition in the A 1Π←X 1Σ+ System of CO
Authors: Tilford S. G. , Simmons J. D.
Published: January 2005

In the fourth positive system, A 1Π←X 1Σ+, of CO, electric quadrupole transitions (ΔJ=2) have been observed for the first time in bands of an electric dipole allowed transition. This system also represents the first example of an electric quadrupole transition to be observed in a heteronuclear diatomic molecule. The quadrupole transition probability has been determined to be ≈1.1×103 sec−1. This value compares well with the value of ≈2.0×103 sec−1 determined for the quadrupole transition probability of the electric dipole forbidden a1 Πg←X 1Σg+ transition in the isoelectronic N2 molecule.
Long-Range Retarded Potentials between Molecules
Authors: Gomberoff L. , McLone R. R. , Power E. A.
Published: January 2005

The retarded interaction between neutral systems with no permanent moments, i.e., relativistic dispersion forces, is analyzed by quantum electrodynamics and the two-photon exchange potential is computed for three cases: (i) When both systems are in their ground states, where the potential is the Casimir—Polder potential which falls off for separations R greater than λ/, the characteristic reduced wavelength in dipole transitions, as R−7; (ii) when one system is in an optically allowed excited state where the potential at short distances is the well-known resonance potential proportional to R−3; and (iii) when both molecules are in excited states. The interaction energies are computed at all separations larger than a few molecular radii, so all overlap and Pauli effects are not considered. The asymptotic forms are given both for R>λ/ and R<λ/ (but still larger than molecular size). The latter give the familiar London and resonance potentials. The former are new results and show a very much slower falloff like a modulated inverse distance or distance squared. This effect is due to the true radiation field of a dipole containing in the radiation zone fields which fall off as R−1. The London potentials, calculated normally by Coulomb interaction only, arise in the fully retarded theory from the near-zone fields which fall off as R−3.
Electron Spin Resonance Studies of Chromium Nitrosyl Complexes
Authors: Danon J. , Panepucci H. , Misetich Antonio A.
Published: January 2005

The electron paramagnetic resonance results of three chromium nitrosyl complexes are reported (pentacyano, penta-aquo, and penta-amino). Hyperfine structure with the nucleus of the metal as well as with the nuclei of some of the ligands is observed. We attempt to explain the interaction with the ligand nuclei by mixing the ground state with excited states (charge transfer) by means of the exchange with the unpaired electron. Different possibilities for the configuration of the ground state are discussed.
Electronic Absorption Spectra of Mn2+, Fe2+, and Co2+ in Dihydrated Halide Crystals
Authors: Lawson Katheryn E.
Published: January 2005

The absorption spectra of Mn2+, Fe2+, and Co2+ in dihydrated halide crystals have been studied as a function of temperature and with polarized incident radiation. The Mn2+ spectrum is quite adequately explained by considering the combined effects of a tetragonally distorted cubic potential and vibrational and/or spin—orbit perturbation on the electronic levels. The data for the Fe2+ and Co2+ crystals support the existence of potential fields of symmetry lower than tetragonal.
Temperature and Pressure Dependence of the Nuclear Quadrupole Resonance of 14N in (CH2)6N4
Authors: Matzkanin G. A. , O'Neal T. N. , Scott T. A. , Haigh P. J.
Published: January 2005

The pure nuclear quadrupole resonance frequency of 14N in hexamethylenetetramine has been studied as a function of pressure and temperature. At constant (atmospheric) pressure the temperature dependence was studied from 4.2° to 340°K. The isothermal pressure dependence was measured at three temperatures, 77°, 196°, and 299°K. These data were analyzed by two methods. In one case, following the method of Brown, the torsional frequency of vibration of the molecules is assumed to decrease as the temperature increases, and this temperature dependence is determined by fitting the quadrupole frequency temperature dependence at atmospheric pressure with Bayer theory. In the second method the volume dependence of the NQR frequency is determined following the method of Kushida, Benedek, and Bloembergen; the parameters involved in this case are found to be intrinsically temperature dependent.
Dipole Moment Function and Vibration—Rotation Matrix Elements for CO
Authors: Young Lee A. , Eachus W. James
Published: January 2005

Electric dipole matrix elements for vibration—rotation transitions in CO have been calculated using a computer program developed by Cooley for the solution of the radial Schrödinger equation. By means of this program four possible cubic dipole moment functions M(r) for CO were obtained from room-temperature measurements of the integrated intensities of the fundamental and first two overtone infrared bands. Relative measurements of rotational line intensities in the overtone bands indicate clearly that the most linear of these four functions is the correct one: M(r)=±0.112+3.11(r−re)−0.15(r−re)2−2.36(r−re)3D. (The internuclear separation r and its equilibrium value, re, are in angstroms.) Using this expression we find in the case of the overtone bands that there is an appreciable deviation of the vibrational matrix elements from the usual binomial expression, and that the matrix elements have a significant rotational dependence.
Fifth Virial Coefficients
Authors: Barker J. A. , Leonard P. J. , Pompe A.
Published: January 2005

A numerical method for evaluating fifth virial coefficients for spherical pairwise-additive potentials is described. Results are given for the case of the Lennard-Jones 12–6 potential.
Statistical Mechanics of Dense Matter: A New Self-Consistent Field Theory
Authors: Barker J. A.
Published: January 2005

A new ``self-consistent field'' method in classical statistical mechanics is described. For lattice systems with nearest-neighbor interactions the method is equivalent to the Bethe or quasichemical approximation. However it is more readily generalized to apply to more complicated systems with further-neighbor interactions, provides insight into the physical meaning of the approximation, and provides the basis for a perturbation theory leading to expansions which are at least formally convergent. Application to lattice models of dense matter leads to integral equations which can presumably be solved by iteration. For a one-dimensional system of hard lines the integral equation derived using the new method and a cell model can be solved exactly and the result is identical at all densities with the known exact expression for the partition function, as it should be since the perturbation corrections all vanish in this case.
Comparison of the Lennard-Jones, exp−6, and Kihara Potential Functions from Viscosity Data of Dilute Argon
Authors: Hanley H. J. M.
Published: January 2005

Experimental viscosity coefficients of argon were used to illustrate how the variation of the parameters of the Lennard-Jones, exp−6, and Kihara functions effect the correlation of the Chapman—Enskog transport theory with experimental data. By rationalizing the choice of the parameters, better correlations were possible than obtained by previous workers and it was shown that the Kihara function gave the best results.
Measurement of Densities and Estimation of Critical Properties of the Alkali Metals
Authors: Dillon I. G. , Nelson P. A. , Swanson B. S.
Published: January 2005

The vapor and liquid densities of the alkali metals rubidium, cesium, sodium, and potassium were measured from room temperature up to near the critical point by a method which utilizes radioactive isotopes of the alkali metals. Critical temperature and critical density were then estimated by several methods of correlation including those of (1) Rowlinson, (2) Cailletet and Mathias, and (3) Kordes, and by a generalized correlation of reduced density versus reduced temperature. Critical temperatures of the alkali metals estimated by these correlating methods were as follows: 2573°±350°K for sodium, 2223°±600°K for potassium, 2093°±25°K for rubidium, and 2057°±40°K for cesium. Corresponding critical densities were: 0.206±0.041 g/cc for sodium, 0.194±0.37 g/cc for potassium, 0.346±0.009 g/cc for rubidium, and 0.428±0.012 g/cc for cesium. The critical temperature and critical density of lithium were estimated using the liquid-density data for lithium reported by Tepper and the generalized correlation of reduced density with reduced temperature. The estimated critical temperature of lithium was 3223°±600°K and the estimated critical density 0.120±0.033 g/cc. The technique used in these measurements involved charging a metal capsule (molybdenum or molybdenum—tungsten alloy) with a calculated amount of alkali metal, sealing the capsule, and irradiating it in a thermal neutron flux to obtain a radioactive isotope of the metal being tested. The irradiated capsule was then placed in an insulated inductively heated high-temperature cell made of molybdenum—tungsten alloy. Gamma radiation emanating from the vapor and liquid regions in the capsule passed through the thin capsule wall (30 mil) and telescoping holes in the high-temperature cell to a sodium iodide crystal outside the furnace. The measured radiation was proportional to the density of the vapor or liquid. While this method of measurement was demonstrated on alkali metals, the technique is general and can be applied in many cases to measure vapor and liquid densities at high temperatures (up to 220°K) for metals, alloys, fused salts, and other materials.
Vibrational and Rotational Excitation of Diatomic Molecules. Two-Dimensional Model
Authors: Benson Sidney W. , Berend George C.
Published: January 2005

The change of energy of a diatomic molecule upon collision with an atom in two dimensions was calculated. The energy contributed to the various internal degrees of freedom of the molecule was evaluated. The vibrational transition probabilities obtained were compared to experimental data for the case of O2→Ar collisions. By contrasting these results with those of a one-dimensional treatment, the form of a realistic three-dimensional potential function was predicted. It was found that at lower initial rotational energies, transfer of energy from rotational to vibrational degrees of freedom is as effective as translational→vibrational transfer. For higher initial rotational energy, rotational→vibrational transfer is shown to be less probable.
High-Temperature Heat Contents and Related Thermodynamic Functions of Eight Rare-Earth Metals: Sc, Gd, Tb, Dy, Ho, Er, Tm, and Lu
Authors: Dennison D. H. , Gschneidner K. A. , Daane A. H.
Published: January 2005

The high-temperature heat contents of scandium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, and lutetium were measured from 0°C to at least the melting points of these metals. The specific heats, heats of transition, heats of fusion, and related thermodynamic functions were calculated. The smoothed values of H°T—H°298.15, (H°T—H°298.15)/T, S°T, and − (F°T—H°298.15)/T are tabulated at 100° intervals. An examination of the entropies of transition and fusion of all of the measured rare-earth metals shows that the entropy of the fcc(or hcp)⇄bcc transition depends upon the number of valence electrons and the entropy of fusion decreases with increasing rare-earth-metal size. The electronic dependence of the entropy of transformation has also been observed to hold for other metals undergoing similar transformations.