bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Photochlorination of Methyl Chloroformate in the Gas Phase
Authors: Brandy J. H. , Le Roy D. J. 
Published: January 2005

Under similar conditions of concentration and light absorption the rate of the gas phase reaction is almost the same as the rate in carbon tetrachloride solution, studied previously, although the mechanism is somewhat different. The gas-phase reaction is not inhibited by products and the bimolecular chain termination step consists in the formation of chlorine, rather than monochloromethyl chloroformate. First-order removal of chlorine atoms becomes important at low light intensities.
The ratio of the rate constant for hydrogen chloride formation to that for first-order chain termination is the same in the gas phase as in carbon tetrachloride solution within the accuracy of the measurements.
Chemical Effects Due to the Ionization of Impurities in Semiconductors
Authors: Reiss Howard 
Published: January 2005

This paper contains a theoretical account of the possible effects which the ionization of donor and acceptor impurities can induce in the thermodynamic phase relations involving their solutions with semiconductors. These effects reflect the energy band structure of the semiconductor. Furthermore, the phenomenon has an interest of its own, for within a certain range of experimental conditions the effects can be attributed to a chemical-like, mass action behavior of the electrons which play the roles of negative ions.
Section V is a brief discussion of a fine point concerning the Fermi level. It is shown that although the Fermi level is certainly the electronic electrochemical potential, it is not the Gibbs free energy per electron unless the density of electron energy levels is linear in the volume of the system.
Hot Atom Chemistry of the Alkyl Bromides; Absence of Effects Due to High Radiation Density; Isotope Separation in Solids
Authors: Rowland Frank S. , Libby W. F. 
Published: January 2005

A 30-curie polonium-beryllium neutron source which gives less than 0.1 roentgen per hour in close contact was used to study the hot atom chemistry of a selection of alkyl bromides. Comparison of the results with those obtained with ordinary neutron sources containing gamma rays in abundance up to 700 roentgen/hour equivalent strongly indicates that the essential phenomena reported are free of effects due to the gamma-radiation density.
The separation of the bromine isotopes in crystalline alkyl bromides has been observed in several additional cases. No isotope effect is shown with CBr4, however, nor with frozen glasses. The possible theoretical significance of these results is discussed.
Infrared Spectra of Gaseous and Crystalline Cyanogen Halides
Authors: Freitag Walter O. , Nixon Eugene R. 
Published: January 2005

The infrared spectra of gaseous ClCN and BrCN at room temperature are reported for the LiF, NaCl, KBr, and CsBr prism regions. Several upper stage bands as well as bands due to C13 appear in both spectra. Assignments are given, from which a number of the vibrational constants are evaluated and the Fermi resonant levels treated by a first-order perturbation method.
The spectra of crystalline ClCN, BrCN, and ICN at −180°C is also recorded. Absorption bands, including several due to C13 and N15, are assigned and the spectra are discussed in terms of the available x-ray crystal data.
Microwave Spectrum and Molecular Structure of Formamide
Authors: Costain C. C. , Dowling J. M. 
Published: January 2005

The microwave spectra of ten isotopic species of formamide (H2N–CHO) have been investigated. Type a and type b transitions have been identified and measured for all ten species. The inertial defect is found to decrease whenever a heavier isotope is substituted for any atom in the NH2 group, and in fact is negative for four of the species studied. It is concluded that the molecule is nonplanar with the H2N–C group forming a shallow pyramid. The structural parameters deduced from the rotational constants are: r(N–H′, where H′ is trans to the aldehyde hydrogen) = 1.014±0.005 A, r(N–H″, where H″ is cis to the aldehyde hydrogen) = 1.002±0.005 A, r(N–C) = 1.376±0.010 A, r(C–H) = 1.102±0.010 A, r(C=O) = 1.193±0.020 A, ∠H′NH″ = 118°53′ ±40′, ∠H″NC = 120°37′±40′, ∠H′NC = 117°9′±40′, ∠NCO = 123°48′±40′, ∠NCH = 113°14′±40′ and ∠OCH = 122°58′±40′. The dihedral angles between the H′NC plane and the NCO plane, and between the H″NC plane and the NCH plane, are 7°±5°, and 12°±5°, respectively.
In all the spectra investigated each line was accompanied by a vibrational satellite line of anomalously high intensity. Measurements of relative intensities were carried out for H2N14–CHO, cis- and trans-HDN14–CHO, and D2N14–CHO. The energy levels (above the zero point) deduced from these measurements show a very large isotope shift, and are interpreted as being due to the first excited state of the NH2 wagging frequency. A pyramidal model for formamide will have two equilibrium configurations separated by a potential barrier. With a Manning type potential, a barrier of 370±50 cm−1, hindering the ``inversion-wagging'' type of motion, is determined. The equilibrium value of the normal coordinate calculated from the Manning potential is found to be in good agreement with that found in the structure determination.
Theory of Ortho-Para Hydrogen Separation by Adsorption at Low Temperatures, Isotope Separation
Authors: White David , Lassettre Edwin N. 
Published: January 2005

A theory of separation of ortho and para hydrogen, by adsorption at low temperatures, is developed by considering the energy levels of a three-dimensional hindered rotator. The Schroedinger equation and boundary conditions are identical with those for prolate spheroidal wave functions and tables of the latter have been employed in calculating the energies as functions of the barrier height. Separation factors, at low surface coverage, have also been computed as a function of barrier height and these pass continuously from unity at zero barrier height over into the limiting separation factor for a two-dimensional rotator (in the adsorbed state) which was used by Sandler in the approximate calculation of separation factors. The theory predicts that ortho hydrogen is more strongly adsorbed than para hydrogen at all barrier heights and that para deuterium is more strongly adsorbed than ortho deuterium. Moreover, the ortho-para hydrogen separation factor is larger at all barrier heights than the para-ortho separation factor for deuterium. These results agree with the experiments of Cunningham, Chapin, and Johnston. Calculated and observed separation factors for hydrogen and deuterium (at low surface coverages) are not in accurate quantitative agreement, however this may be due to the fact that experimental separation factors for both isotopes were not determined under comparable conditions. Calculations have been made first by assuming that rotation and (center of mass) vibration are separable. This model is then refined to take into account the interaction of rotation and vibration.
The separation of the hydrogen-deuterium isotopes is also considered. Although the inclusion of interaction between vibration and rotation does not greatly change the ortho-para separation factors, this effect has a marked influence on the calculated isotope separation factors. It is of considerable interest that isotope separation factors are strongly dependent on the ortho-para composition of the isotope mixture, at least at low surface coverages, in the theory developed here.
Dissociation of Halogens in Shock Waves
Authors: Hiraoka Hiroyuki , Hardwick R. 
Published: January 2005

The rate of dissociation of Cl2 has been measured at high temperatures in a shock tube. The temperature dependence curves, regardless of Cl2 concentration, are fitted by invoking 4° of freedom of internal motion and an activation energy of 48 kcal.
From the temperature TH at which the decrease of Cl2 optical density through dissociation matches the increase due to the cooling, by reaction enthalpy, the dissociation energy of Cl2 has been calculated. The agreement with the well-known spectroscopic value gives a confirmation of the shock-tube temperature measurements and of many assumptions made in the other calculations.
On the Vapor Pressure of Electrically Charged Droplets
Authors: Gallily Isaiah , Ailam (Volinez) Gedalia 
Published: January 2005

A general expression is derived for the vapor pressure of a charged drop situated at the center of a spherical container with perfectly reflecting wall. It is assumed that the liquid is conducting, the medium devoid of external fields of force and that the gaseous phase comprises both neutral and charged molecules. The vapor pressure in the case where the radius of the container is close to that of the drop was evaluated after solving the equation for the distribution of the charged molecules near the surface.
It was shown that, in general, the vapor pressure tends to infinity with increasing distance from the droplet, thus rendering impossible the attainment of a thermodynamic equilibrium in the atmosphere. The vapor pressure of a charged mercury droplet is given as a numerical example.
Higher-Order Rotation-Vibration Energies of Polyatomic Molecules. V
Authors: Amat Gilbert , Nielsen Harald H. 
Published: January 2005

The Schrödinger equation for the energies of a rotating-vibrating polyatomic molecule is not exactly soluable. The common procedure is to expand the Hamiltonian for the problem in orders of magnitude, the parameter of smallness being of the order of (Be(αα)/ωs)½, where Be(αα) is a rotational constant and ωs is a vibration frequency, and to arrive at energy expressions by successive approximations.
The actual order of magnitude of a term in the Hamiltonian will depend upon the values of (Be(αα)/ωs) and the values of the rotational quantum numbers relative to the vibration quantum numbers. One may, therefore, use different expansions for the quantum mechanical Hamiltonian corresponding to the values of J and K taken under consideration, in which case the ``index'' of magnitude of the matrix element of an operator O belonging to the Hamiltonian operator hm, expansion for the Hamiltonian H as has been done by Goldsmith et al., whatever the values of the quantum numbers may be, accepting then that the true ``index'' of magnitude is not necessarily equal to m.
Adopting the latter scheme and using the expansion of the Hamiltonian proposed by Goldsmith et al. the contributions to the energy of the various terms comprising it are considered for various ranges of J and K and an assignment of the order of magnitude to which the contribution belongs is made.
Rotational Isomerism and Microwave Spectroscopy. I. The Microwave Spectrum of Normal Propyl Fluoride
Authors: Hirota Eizi 
Published: January 2005

The normal propyl fluoride molecule has been confirmed by microwave spectroscopy to exist in two rotational isomers, trans and gauche. Rotational constants in the ground vibrational state are A = 26 986.73, B = 3748.32, C = 3509.88 Mc/sec for the trans form and A = 14 503.69, B = 5085.71, C = 4295.28 Mc/sec for the gauche form. The dihedral angle of the gauche form is about 63° from the cis position.
The barrier height hindering methyl rotation has been determined, using lines in the first excited state of methyl rotation, to be 2.69 kcal/mole and 2.87 kcal/mole for the trans and the gauche forms, respectively. The dipole moment and its components along the principal axes have been determined by the Stark effect: μa = 1.970±0.026, μb = 0.566±0.064, μtotal = 2.050±0.043D for the trans form and μa = 1.137±0.008, μb = 1.450±0.033, μc = 0.472±0.137, μtotal = 1.902±0.064 D for the gauche form. The total dipole moment is nearly parallel to the C–F bond for both forms; the angle between them is 10.6° in the trans form and 7.4° in the gauche form.
The intensities of satellites due to the first and the second excited states of the C–C torsion have been measured relative to the ground-state lines. The energies of the first and the second excited states are 98.0 cm−1 and 211.3 cm−1 for the trans form and 160.8 cm−1 and 322.6 cm−1 for the gauche form. The same technique of the relative-intensity measurement has been applied to the temperature dependence of the intensity ratio of trans and gauche lines, giving the result that the gauche form is more stable than the trans form by 0.47±0.31 kcal/mole. Using these data the first seven constants were determined in the Fourier expansion of the potential function around the central C–C bond. The barrier at the cis position seems to be higher than that separating the trans form from two equivalent gauche forms.
Photolysis of Diborane at 1849 Å
Authors: Kreye W. C. , Marcus R. A. 
Published: January 2005

The photolysis of diborane at 1849 Å has been studied in a specially constructed, internal-type mercury-vapor lamp. The products have been found to be H2, B4H10, B5H11, and, at low pressures, a —BH— polymer. Reaction orders at 4°C have been obtained from linear plots of reaction products vs time for a range of diborane pressures from 0.08 to 80 cm, and at two light intensities. Linear relations between products and time existed only at very low conversions (∼1%), which required the development of a low-temperature separation method for manipulating and analyzing the traces of B4H10 and B5H11. Because of the reactivity of these compounds, a detailed conditioning procedure was employed for the glass system.
A mechanism consistant with the kinetic data and suggested by the kinetic results of thermal and photosensitized decomposition of diborane is postulated: the B5H11 is assumed to be formed from a dissociation of B2H6 into BH3's, the latter arising from an excited molecule. The B4H10 and polymer are assumed to be formed from a dissociation of B2H6 into B2H5 and H, followed by radical recombination. There is a significant difference between the kinetics of thermal and photochemical B5H11 formation, a result which may be due to the considerable energy excess of the 1849 quantum over that needed for dissociation (∼125-kcal excess). These kinetic results raise a number of interesting questions, questions which can only be resolved through further investigations of effects due to light intensity, added inert gases, and temperature.
The primary quantum yield of the step forming B2H5 and H is about 10 times higher than that of the one forming BH3's. A rather rough estimate suggests that the former is of the order of magnitude of unity.
Mass Spectral Studies of Kinetics behind Shock Waves. II. Thermal Decomposition of Hydrazine
Authors: Diesen R. W. 
Published: January 2005

The decomposition of hydrazine diluted in argon has been studied over the temperature range 1200° to 2500°K and pressure range 0.04 to 0.25 atm using a shock tube coupled to a time-of-flight mass spectrometer. The time-resolved mass spectra (25 μsec) enable the simultaneous identification and determination of N2H4, NH3, N2, H2, and the NH2 radical, the five major species observed. The material balance is within the experimental error (10%) during reaction up to complete decomposition.
The primary process in the dissociation of hydrazine is shown to be the rupture of the N–N bond to give NH2 radicals. The observed rate constants for the disappearance of hydrazine are those expected of a unimolecular reaction: N2H4+M→ lim k1N2H4*,N2H4*→ lim k22NH2,at or near the second-order region where the collisional activation (1) is rate controlling. At the higher temperatures, the results are consistent (within experimental error) with the very simple reaction scheme of Reaction (1) and (2) followed by NH2+NH2→ lim k3NH3+NH,NH+NH→ lim k4aN2H2*→ lim k4bN2+H2.At the lowest temperatures the reaction NH2+N2H4→N2H3+NH3 appears to become important.
From the experimental concentrations, a value of k3=2.5×1013 cc/mole−sec (2000∘K)is obtained. An order-of-magnitude estimate gives k4∼1014 cc/mole−sec (2000∘K).
Dissociation of H2 and Other Diatomic Molecules by Neutron Bombardment
Authors: Clendenin W. W. 
Published: January 2005

The perturbation treatment of neutron scattering introduced by Fermi is extended to the case of dissociation of diatomic molecules. In contrast to the usual determination of the kinematics of one fragment only, in the present calculation the detailed energy distributions of both fragments of the dissociated molecule are obtained. The theory has been applied in the cases of the ground states of H2, N214, Cl235 and HCl35.
The necessary conditions on perturbation theory to provide a correct treatment of recoil effects are examined and discussed.
Exciton Magnetic Resonance in Wurster's Blue Perchlorate
Authors: Thomas D. D. , Keller H. , McConnell H. M. 
Published: January 2005

The paramagnetic resonance of a single crystal of Wurster's blue perchlorate (a solid ionic free radical) in the 20°—77°K temperature range provides evidence that the elementary electronic excitations are triplet excitons with excitation energy J=246 cm−1. Exciton motion is indicated by the absence of nuclear hyper-fine structure at low exciton concentrations where exciton—exciton spin exchange interaction is negligible. Exciton motion is thought to be primarily along linear free-radical chains; the rate of chain jumping is estimated to be greater than 50 Mc/sec but probably less than 103−104 Mc/sec.
At certain crystal orientations in a strong magnetic field the rate of exciton chain jumping is large compared to the difference in the fine-structure splitting of excitons on the two linear chains in the low-temperature monoclinic crystal; in this case the (three-dimensional) exciton spin Hamiltonian, H=E(Sx2−Sy2), with | E | = 212 Mc/sec, accounts for the observed splittings to within 2%. At other crystal orientations the fine-structure lines are lifetime broadened (due to chain jumping) so much that they are not observable.
The well-known sudden decrease in magnetic susceptibility of Wurster's blue perchlorate at 186°K is apparently due to an orthorhombic→monoclinic phase transition in which the Wurster's blue cations pair up to form dimers with ground singlet states and excited triplet states. The observed value of E can, however, be estimated theoretically with good accuracy in terms of the known intermolecular distances for the room-temperature orthorhombic lattice and a molecular orbital approximation for the spin distribution in the positive ions. This suggests that the dimerization involves only small molecular displacements in the crystal lattice.
Crystallography of Impurity Adsorption on Copper Surfaces
Authors: Robertson W. M. , Shewmon P. G. 
Published: January 2005

The object of the investigation was to determine the sites at which impurity adsorption occurs on crystalline surfaces. This was done by measuring the variation of surface free energy (γ) with orientation (θ). A relation between the torque [τ=(∂γ/∂θ)μ], chemical potential (μ), surface excess (Γ), and orientation is derived: (∂τ/∂μ)θ = — (∂Γ/∂θ)μ. Methods for determining surface torques by measuring dihedral angles at grooves where twin boundaries and grain boundaries intersect surfaces are discussed.
Measurements were made of relative torques τ/γ on copper surfaces for the range of oxygen pressures from 10−22 to 10−13 atm at 1000°C using water—hydrogen mixtures. Increasing po2 was found to increase the magnitude of the torque on the (111) and (100) orientations. This indicates preferential adsorption at a range of orientations on the smooth, low-index (100) and (111) surfaces rather than on stepped surfaces of orientations different from the low-index orientations.
A calculation based on a simple model of the surface indicates that about a half monolayer of oxygen atoms is adsorbed on the (111) surface. The characteristic pressure for oxygen adsorption on (111) was calculated to be 3×10−17 atm oxygen at 1000°C.
Measurements of torques after annealing in an atmosphere containing hydrogen sulfide showed that sulfur adsorption decreases the torque near (100) while not affecting that near (111). This indicates preferential sulfur adsorption at steps near the (100) orientation.
Integration of the plots of torque as a function of orientation showed that the surface energies of (100) and (111) relative to higher index surfaces are lowered as the oxygen pressure is increased.
Poincaré Cycles, Ergodicity, and Irreversibility in Assemblies of Coupled Harmonic Oscillators
Authors: Mazur Peter , Montroll Elliott 
Published: January 2005

The transport coefficients (diffusion constant, electrical conductivity, etc.) associated with irreversible processes in an assembly of particles can be expressed as integrals over certain time relaxed correlation functions between small numbers of variables of the assembly. The scattering of slow neutrons is also a measure of time relaxed correlation functions.
Irreversibility is a consequence of the vanishing of the correlation coefficients as the relaxation time becomes infinite. On the other hand these coefficients have Poincaré cycles so that any value which they take on is repeated an infinite number of times. It is shown that, in the case of fluctuations of 0(N−½) from zero (N being the number of degrees of freedom), the period of Poincaré cycles is of the order of the mean period of normal mode vibrations while for fluctuations of a magnitude independent of N the period is of the order of CN where C is a constant which is greater than 1.
The time relaxed correlation coefficients of a pair of particles separated by r lattice spacings decays as t−m/2, m being the number of dimensions of the assembly. The statistics of the decay of the momentum of a particle from a preassigned initial value to its equipartition value are discussed.
Variational Method for Studying the Motion of Classical Vibrating Systems
Authors: Luttinger J. M. , Thomas R. B. 
Published: January 2005

A quantity Z (essentially the action integral) is shown to be stationary for small periodic deviations from the actual motion. By choosing approximations to the motion containing the frequency and some other parameters, it is possible to make this variational principle the basis of an approximate determination of the motion.
Quite simple trial functions are found to give surprisingly accurate values for the frequency and the Fourier components of the motion. Comparison between the exact solution and ours for some systems is given.
Invariant Imbedding and Mathematical Physics. I. Particle Processes
Authors: Bellman Richard , Kalaba Robert , Wing G. Milton 
Published: January 2005

With the use of invariance principles in a systematic fashion, we shall derive not only new analytic formulations of the classical particle processes, those of transport theory, radiative transfer, random walk, multiple scattering, and diffusion theory, but, in addition, new computational algorithms which seem well fitted to the capabilities of digital computers. Whereas the usual methods reduce problems to the solution of systems of linear equations, we shall try to reduce problems to the iteration of nonlinear transformations.
Although we have analogous formulations of wave processes, we shall reserve for a second paper in this series a detailed and extensive treatment of this part of mathematical physics.