bluuebunny/crossref_metadata_2025 huggingface dataset:
Generalization of Quasichemical Formulas
Authors: Guggenheim E. A. , McGlashan M. L.
Published: January 2005

Quasichemical formulas have been generalized so as to be applicable to any chosen group of sites on any chosen lattice. The resulting formulas have been applied to two examples not previously discussed—namely, cubic octets on a simple cubic lattice and cagelike decets on a diamond lattice.
27Al Nuclear Magnetic Resonance of Trialkyl Aluminum Compounds. I. Room-Temperature Studies
Authors: Poole Charles P. , Swift Harold E. , Itzel John F.
Published: January 2005

The compounds triethylaluminum, tri-n-propylaluminum, tri-n-butylaluminum, and tri-n-hexylaluminum were studied by nuclear magnetic resonance both in the pure state and in the solvents isopentane, n-hexane, cyclohexane, and hexadecane. At low viscosities the linewidth was proportional to the viscosity times the cube of the molecular radius, and it is believed that the dominant relaxation mechanism is quadrupolar relaxation through molecular rotation. In high-viscosity solvents this mechanism becomes unimportant. A mixture of aluminum alkyls produces a single Lorentzian shaped resonance which arises from rapid alkyl interchange.
Structure of the Xp Matrices in the Simple Harmonic Oscillator Representation
Authors: Kilpatrick John E. , Sass Ronald L.
Published: January 2005

The m, n element of Xp in the one-dimensional simple harmonic oscillator representation is shown to be in the form 〈m | xp | n〉=βp|2[(N−r+1)(N−r+3)(N−r+5)···(N+r−1)]12(p12(p−r))2−p/2Frp(N),where N=m+n+1, r=m—n, β=ℏ/2μω and Frp(N) is a simple polynomial in N, purely even or odd and with small, positive, integral coefficients. A number of simple recursion relations are developed for the F polynomials.
Collision Frequency of Molecules Excited by Monochromatic Light
Authors: Kummler Ralph H. , McCarty M.
Published: January 2005

The variation in intensity of the exciting line across the absorption line in fluorescence spectra excited by monochromatic light is shown to result in a non-Maxwellian velocity distribution of the excited molecules. Expressions for the collision frequency and velocity distribution of the excited molecules are derived, assuming that the fluorescence exciting line is Gaussian and that the absorption line is primarily Doppler broadened. Neglect of this effect can lead to errors of over 25% in total collision frequency and over 100% for particular ranges of relative kinetic energy of the colliding molecules. The relevance of the non-Maxwellian character of the velocity distribution to energy-transfer investigations is discussed. In particular, this effect may obscure any variation in collisional energy-transfer cross sections with vibrational level.
Infrared Spectra and Normal Coordinate Analysis of Metal Glycino Complexes
Authors: Condrate Robert A. , Nakamoto Kazuo
Published: January 2005

The infrared spectra of bis(glycino) complexes of Pt II, Pd II, Cu II, and Ni II have been measured from 4000 to 250 cm−1. For cis-bis(glycino) Cu II monohydrate, the spectra have been obtained including its three deutero analogs. Normal coordinate analyses have been carried out on all these complexes using the 1:1 (metal/ligand) approximation. The results indicate that the metal—nitrogen stretching bands are located between 550 and 430 cm−1 and the metal—oxygen stretching bands are between 420 and 290 cm−1. The metal—nitrogen and metal—oxygen stretching force constants have the same value for each metal studied, and are 2.10, 2.00, 0.90, and 0.70 mdyn/Å for Pt II, Pd II, Cu II, and Ni II, respectively.
Paramagnetic Resonance and Optical Properties of Amethyst
Authors: Barry Thomas I. , McNamara Peter , Moore Walter J.
Published: January 2005

Color centers in amethyst are produced by action of ionizing radiation on precursor centers which arise from substitution of Fe3+ for Si4+ in the α-quartz structure, with charge neutralization usually achieved by an alkali-metal ion on the twofold axis of the center. These Fe3+ centers provide the dominant features of the electron paramagnetic resonance spectrum of amethyst, which was measured in the X-band at room and liquid-nitrogen temperatures. The spectrum was fitted to an orthorhombic spin Hamiltonian with g=2.0032, D=−2.0463, E=5.5277, F=−0.0282 Gc/sec. The optical biaxiality of amethyst, with biaxial angle 2V=6 to 12°, is due to unequal occupation of the three equivalent Si4+ sites in the structure by Fe3+ during crystal growth. This phenomenon may help to specify geological conditions during hydrothermal growth of natural amethyst.
Vibrational Selection Rules for Dimethylacetylene
Authors: Bunker Philip R.
Published: January 2005

The molecular symmetry group of dimethylacetylene was defined by Longuet-Higgins, and its double group was introduced by Hougen. In this paper we determine the form of the normal coordinates of dimethylacetylene and classify them in the double group. Using the exact normal coordinates it is not always possible to obtain selection rules on purely vibrational transitions. However, by approximating the potential function we can obtain ``approximate normal coordinates'' and, thereby, derive ``approximate vibrational selection rules.'' These selection rules prove useful in interpreting the infrared and Raman spectra of dimethylacetylene and other ethanelike molecules that have a low torsional barrier. One important result is that we do not generally expect there to be any coincidences between infrared and Raman fundamental bands.
Thermoelectricity in Irradiated Dielectrics. I. Some General Features
Authors: Hardtke F. C.
Published: January 2005

A transitory charge displacement has been observed in gamma-irradiated solid dielectrics when the 3.2-mm-thick samples are heated subsequently in temperature gradients of 5 to 40 C°/mm. The charge displaced was found to be directly proportional to the temperature gradient and, below a megaroentgen, to the radiation exposure. With further exposure it approaches a maximum of a few nanocoulombs per square centimeter. Electric fields above 100 V/mm applied to the sample during heating produce only slight changes in the magnitude of the thermoelectric discharge. A marked reduction in the discharge magnitude is observed in samples that are shielded from the radiation source by metal plates approximately 0.1 g/cm2 thick. This suggests that the phenomenon may arise from the thermal release of trapped electrons which have entered the sample as Compton recoils.
Radiationless Transitions and Deuterium Effect on Fluorescence Lifetimes of Some Aromatic Hydrocarbons
Authors: Laposa Joseph D. , Lim E. C. , Kellogg R. E.
Published: January 2005

The fluorescence lifetimes of several perprotonated and perdeuterated aromatic hydrocarbons have been measured in rigid media at 77°K. Within experimental error, no change is found in lifetime upon substitution of deuterium for protium. It is concluded from this result that radiationless first excited singlet to ground singlet (S1→S0) transitions are unimportant in these systems. The fluorescence lifetime of anthracene at room temperature also compares favorably with that at low temperature, suggesting strongly that S1→T1 (first excited singlet to lowest triplet) radiationless processes in aromatics are temperature independent.
Diffusion-Controlled Quenching at Higher Quencher Concentrations
Authors: Reck R. A. , Prager Stephen
Published: January 2005

A variational procedure is employed to establish rigorous upper and lower bounds on the rate of a diffusion-controlled reaction, in which an excited species B* is generated at a constant and uniform rate throughout a solution containing a quencher species A. De-excitation is assumed to occur instantaneously whenever a B* molecule has diffused to within a critical distance a of a quencher particle; the Brownian motion of the quencher itself is neglected. Results are obtained in terms of various statistical characterizations of the distribution of A particles in the solution. Explicit calculations have been carried out for the case where the quencher molecules exert no forces upon one another or upon the B* species.
On the Calculation of the Dispersion-Forces Coefficient Directly from Experimental Transport Data
Authors: Munn R. J.
Published: January 2005

A method of calculating the dispersion-forces coefficient from low-temperature experimental transport cross sections is developed. The method is used to calculate the dispersion-forces coefficients of neon and argon from low-temperature viscosity data. Good agreement with the sum-rule calculations of Dalgarno and Kingston is found.
On One-Center Expansions in H2+
Authors: Joy Hubert W. , Handler George S.
Published: January 2005

An analysis of several alternative forms of one-center expansion of the ground-state H2+ wavefunction is presented in the context of a comparison of three recent one-center expansions, together with new numerical results. A 14-term one-center function having energy −1.10121 hartree is given.
Crystal and Molecular Structure of Hydrogen Peroxide: A Neutron-Diffraction Study
Authors: Busing William R. , Levy Henri A.
Published: January 2005

The coordinates and thermal parameters of the O and H atoms in solid H2O2 have been determined by a single-crystal neutron-diffraction study. Final values were obtained by least-squares refinement based on 91 observed intensities of the hk0, hhl, and h0l reflections. The molecular parameters (uncorrected for the effect of thermal motion) are as follows: O–O distance, 1.453±0.007 Å; O–H distance, 0.988±0.005 Å; O–O–H angle, 102.7±0.3°; dihedral angle between the two O–O–H planes, 90.2±0.6°. Hydrogen bonding occurs with an O–H···O distance of 2.799±0.008 Å. The O–H bond distance corrected for thermal motion is 1.008±0.005 Å.

Comparison of these results with those reported by others from studies of H2O2 vapor and of various crystals containing H2O2 indicates that the dihedral angle is quite sensitive to the environment of the molecule.
Effect of External Heavy Atoms on Decay Processes from the Triplet State
Authors: Siegel Seymour , Judeikis H. S.
Published: January 2005

An investigation was made to determine the relative sensitivities to the external heavy-atom perturbation of the radiative (kp) and the nonradiative (kqp) decay constants for the return of aromatic molecules in their first triplet state to the ground state. The investigation was carried out in glasses at 77°K using alkyl halide and ethanol mixtures as solvents. A combination of EPR and optical emission spectroscopy was used as the diagnostic technique. The results of the study show that kp is more sensitive than kqp to the nature of the heavy atom in the solvent. It is also found that kIS (the intersystem crossing rate constant) is less sensitive than kp to the heavy-atom perturbation. Finally, analysis of the data indicates not only that kqp is not totally quenched upon perdeuteration of naphthalene but also that kqp>kp in naphthalene-d8 in ethanol.
Electron-Diffraction Study of the Structure of B(CH3)3
Authors: Bartell L. S. , Carroll B. L.
Published: January 2005

The molecular structure of gaseous B(CH3)3 was determined by the sector-microphotometer method of electron diffraction. Essentially free rotation of methyl groups was found. Mean bond lengths and standard errors were B–C=1.5783±0.0011 Å and C–H=1.1138±0.0015 Å. The angles CBC and BCH computed from mean distances, ignoring shrinkage effects, were 119.4°±0.3° and 111.9±0.2°, respectively. Shrinkage corrections would add roughly 0.5°. Root-mean-square amplitudes of vibration were lBC=0.0536±0.0012 Å, lCH=0.0811±0.0018 Å, lC···C=0.0762±0.0017 Å, and lB···H=0.1256±0.004 Å. Methyl groups differed significantly from CH3 groups in methane but not from methyl groups in ethane. Bond lengths and amplitudes provided no evidence for hyperconjugative stabilization.
Surface Tension of the {100} Face of Alkali Halide Crystals
Authors: Benson G. C. , Yun K. S.
Published: January 2005

In this paper, the distinction between the surface free energy (or surface energy at 0°K) and surface tension is re-examined. The change in the state of stress in a crystal associated with the presence of the surface is represented by the surface stress tensor. The mechanical definition which is adopted for this tensor, is similar to that used in the theory of the surface tension of liquids. The surface tension is a scalar quantity related to the trace of the surface stress tensor.

Results of calculations of surface tensions are reported for the {100} face of all the alkali halides with the NaCl structure. The model used is the same as that employed in previous calculations of the surface energies of these crystals, and includes a consideration of distortion effects (displacement and polarization of the ions) occurring in the surface region. Positive surface tensions were found for all of the alkali halides investigated.
Microwave Double-Resonance Experiments
Authors: Cox A. P. , Flynn G. W. , Wilson E. B.
Published: January 2005

Double quantum transitions and certain changes in line intensities which can be ascribed to relaxation effects have been observed in a Stark-effect spectrometer in which the absorbing gas was exposed to two microwave fields simultaneously. The general features of the line shape predicted by Javan for a three-level system in the presence of two irradiating fields have been clearly observed in OCS and propylene oxide. Studies of various transitions in these molecules indicate the presence of either a double quantum emission or absorption line depending upon the energy-level scheme in question. Observation of both zero-field and Stark transitions has revealed certain expected changes in line intensities. Several experimental arrangements for microwave double resonance are described and applications of this technique to the identification and confirmation of complex rotational spectra are discussed.
Vacuum-Ultraviolet Photolysis of Acetylene
Authors: Stief L. J. , DeCarlo V. J. , Mataloni R. J.
Published: January 2005

The vacuum-ultraviolet photolysis of acetylene has been investigated at the Kr (1236 Å, 1165 Å) and Xe (1470 Å, 1295 Å) resonance lines. Evidence is presented for production of a long-lived excited state of acetylene. Decomposition of the excited state at low pressure leads to the formation of molecular hydrogen and excited C2. At the Kr resonance lines and at the 1295-Å Xe line, an emission consistent with Swan bands (A 3πg→X 3πu) of C2 is observed at low pressures. No emission is observed in the photolysis of acetylene at 1470 Å. Intensity of the emission, the quantum yield for hydrogen production, and the quantum yield for acetylene disappearance are all greatly reduced by the addition of a few millimeters of a quenching gas. Decomposition to H2 and C2 also occurs in the solid phase.

The over-all photolysis is explicable in terms of an excited molecule mechanism. Formation of C2 in excited A 3πg state depends on the energy of the incident photon: C2H2+hv→C2H2*,C2H2*+M→C2H2+M,C2H2*+C2H2→C4H4*,C4H4*→C2H2‡+C2H2‡,C2H2*→C2(A 3πg)+H2,C2(A 3πg)→C2(X 3πu)+hv,C2H2*→C2+H2,C2H2*→C2H+H,H+C2H2→C2H3,C4H4*+C2H2→C6H6*,etc.,C4H4*+C2H2→C4H4(vinyl acetylene)+C2H2,C6H6*+C2H2→C6H6+C2H2,2C2H→C4H2(diacetylene)
Photochemical Charge-Transfer Reactions in Frozen Aqueous Systems. I. Electron Transfer from the Solute to the Matrix
Authors: Moorthy P. N. , Weiss J. J.
Published: January 2005

Hydrogen-atom ESR signals have been detected at 77°K in ultraviolet-irradiated frozen acid solutions when the latter contain solutes such as I— and Fe2+, which are characterized by charge-transfer spectra in the ultraviolet. The quantum yield of hydrogen-atom formation has been studied as a function of the solute concentration and of the nature and concentration of the acid present in the matrix. The results can be explained on the assumption that ultraviolet irradiation leads to a charge transfer, giving in the first instance an excited state in which the electron is transferred, to a greater or lesser extent, to the hydration shell where it is bound in the field of the oriented water molecules around the ion. The electron in the excited state can either revert to the ground state or may react with electron acceptors present in the matrix, where their reaction with, e.g., acids leads to the formation of H atoms. It has been found that the excited ion can apparently also be deactivated by interaction with another like ion in the ground state. This is suggested by the observation that with increasing concentration of the light-absorbing ions the H-atom yield decreases.
Velocity of Sound in Nitrogen and Argon at High Pressures
Authors: El-Hakeem A. S.
Published: January 2005

Measurements of the velocity of sound in N2 and Ar are reported at the ice point and 294.26°K (70°F) and at pressures between 1 and 70 atm. The ratio of the specific heats as a function of pressure and temperature was calculated from the experimental results.
On the Kinetic Theory of Dense Fluids. XIX. Comments on and a Rederivation of the Kinetic Equations
Authors: Hiroike Kazuo , Gray Peter , Rice Stuart A.
Published: January 2005

In this paper we rederive the Rice—Allnatt kinetic equation and show that, for the soft-force part of the interaction, the constant friction-coefficient Fokker—Planck operator is the first approximation to a more complex operator. This more complex operator is of the general Fokker—Planck form, but has momentum-dependent friction coefficients. The operator derived herein is identical with the operator obtained from the Prigogine theory in the weak coupling limit.

The consistency between the Rice—Allnatt analysis of transport in liquids and the exact perturbation analysis of Prigogine is examined, as is the internal consistency of the Rice-Allnatt analysis. At present, there appear to be no inconsistencies between the two theories.
Molecular Energy States and the Thermodynamic Properties of Solid Isotopic Methanes
Authors: Colwell J. H. , Gill E. K. , Morrison J. A.
Published: January 2005

The heat capacities of the partially deuterated methanes, CH3D, CH2D2, and CHD3, have been measured between 2.5° and 27°K. In addition to the known transitions (two in each methane in the region 16°<T<26°K), each substance displays a large heat-capacity anomaly at lower temperatures (T<8°K). Time effects were only observed with CH3D and it is suggested that these were caused by CH4 impurity in this methane.

None of the methanes was isotopically pure; the low-temperature properties of the ``pure'' methanes were estimated by assuming the heat capacities of the different isotopic species to be additive. On this basis, and neglecting the anomalies at the lowest temperatures, the residual entropies (i.e., the differences between the practical and the calorimetric entropies) are found to be very close to R ln4 for CH3D and CHD3 and to R ln6 for CH2D2. These results are to be compared with the values ∼0 and −0.58 cal/mole·deg for CD4 and CH4, respectively.

Results of magnetic resonance and spectroscopic experiments and information derivable from the thermodynamic properties of CH4 and CD4 at higher temperatures all indicate that intermolecular coupling in the methane lattices is relatively weak. For this reason, the properties of the solid methanes at the lowest temperatures are interpreted as resulting from separate contributions of lattice vibrational and perturbed molecular (rotational) energy levels. It is concluded that the residual entropies and the heat-capacity anomalies are related and that their origin is in the molecular energy states of the systems. We make a quantitative analysis of the thermodynamic data for all of the isotopic methanes, taking explicit account of the degeneracies of the different nuclear-spin species. The results are shown to be consistent with the known molecular symmetries and two particularly simple crystal site symmetries.
Mass-Spectrometric Studies of Atomic Reactions. V. The Reaction of Nitrogen Atoms with NO2
Authors: Phillips L. F. , Schiff H. I.
Published: January 2005

The reaction of N atoms with NO2 has been studied in a fast flow system, using a mass spectrometer to monitor the composition of the reaction mixture. The rate constant for removal of NO2 by N was found to be (1.85±0.22)×10−11 cm3 molecule−1·sec−1. By a combined mass-spectrometric and photometric method the relative contributions of the different primary reactions have been determined as follows (errors shown are standard deviations): N+NO2→N2O+O (0.43±0.04),N+NO2→2NO (0.33±0.07),N+NO2→N2+O2 (0.10±0.12),N+NO2→N2+2O (0.13±0.11).
Matrix-Isolation Study of the Reaction of F Atoms with CO. Infrared and Ultraviolet Spectra of the Free Radical FCO
Authors: Milligan Dolphus E. , Jacox Marilyn E. , Bass Arnold M. , Comeford J. J. , Mann D. E.
Published: January 2005

FCO has been obtained in a CO and in an Ar matrix at 4°, 14°, and 20°K by the reaction with CO of F atoms produced upon photolysis of OF2, of NF2, or of t-N2F2, as well as by the photolysis of F2CO or of HFCO. The three vibrational fundamentals of the free radical FCO appear at 1855, 1018, and 626 cm−1. Experiments employing 13C16O and 12C18O confirm the infrared identification of FCO. In ultraviolet-absorption studies on matrix-isolated FCO an extensive series of bands has been observed between 2200 and 3400 Å. The most prominent progression in this system involves bands spaced at approximately 650-cm−1 intervals. It is likely that this progression is associated with the upper-state bending mode of FCO. F2CO and (FCO)2 are also produced in the reaction of F atoms with a CO matrix, and features of their infrared spectra are reported. A supplementary observation of the ultraviolet-absorption spectrum of gaseous F2CO shows a band system between 1800 and 2100 Å, with spacings of approximately 1700 cm−1. Presumably this system is contributed by the n→π* carbonyl transition. The approximate geometric structure and the nature of the chemical bonds of FCO are discussed, and the mechanisms of formation of this species and of the other observed products are considered. An estimate of the thermodynamic properties of FCO is given.
Ionization of H2 by Electron Impact near Threshold
Authors: Briglia Donald D. , Rapp Donald
Published: January 2005

The cross section for ionization of the hydrogen molecule by electron impact near threshold has been experimentally studied in a total-ionization tube. Careful attention has been given to consistency checks to ensure complete collection of electrons and ions. The cross section was found to be essentially a linear function of the electron-energy excess above threshold for ∼4 eV above threshold. Similar results were obtained using a dc electron beam, and using a double-phase sensitive detection ac variation of the RPD method to reduce the energy spread to ∼0.06 eV at half-height. These results are in disagreement with the threshold law predicted by a simple direct-ionization model, and imply that some indirect process such as autoionization is playing a major role in the ionization process. Thus the distribution of vibrational states in the H2+, which plays a major role in inelastic collisions of H2+ with atomic particles, is not correctly predicted by the direct ionization model. Evidently, the ionization of a simple molecule like H2 near threshold is too complicated a process to be adequately described in terms of existing models.
Intermediate Coupling Energy Levels for Nd3+(4f3) in LaF3
Authors: Caspers H. H. , Rast H. E. , Buchanan R. A.
Published: January 2005

The absorption spectrum of Nd3+(4f3) has been investigated in the spectral region 4100 to 60 000 Å. Fluorescence at 77° and 4.2°K has been observed corresponding to transitions from the excited 4F3/2 levels to all the Stark components of the 4I9/2 and 4I11/2 levels.

By means of a least-squares method, we have calculated the Slater and spin—orbit parameters from experimentally observed levels whose LSJ assignments are reliable. The values of these parameters giving a best fit between the predicted free-ion spectrum and the spectrum of Nd3+ in LaF3 are F2=338.439 cm−1, F4=47.153 cm−1, F6=5.579 cm−1, and ζ=882.109 cm−1. The average deviation of eight of these levels is 10 cm−1.
Electronic Spectra of Methyldifluoramine and Perfluoromethyldifluoramine
Authors: Chien James C. W.
Published: January 2005

The electronic spectrum of perfluoromethyldifluoramine, CF3NF2, in the 2800- to 3600-Å region consists of two V progressions corresponding to transitions: (1) 1A(core)(as′)1(ā′)1v4′(a′)←1A(core)(as′)2v4′′(a′),  ΔV=0,1,2,3,···,where the frequencies ν4″ (a′) =642 cm−1, ν4′ (a′) =528 cm−1, and (ā′) is the NF antibonding molecular orbital (MO); and (2) 1A(core)(as′)1(ā1′)1v5′(a′′)←1A(core)(as′)2v5′′(a′′),  ΔV=0,2,4,6,···,where the frequency ν5′ (a″) =710 cm−1. Absorptions by CH3NF2 in the same region are attributed to the transition 1A (core) (a″)1(ā′)1←1A (core) (a″)2 involving the same vibrational couplings as above. Both spectra showed continuous absorptions below 2500 Å.
On the Calculation of Potential Curves by the Rydberg—Klein—Rees Method. I. Experimental Limitations, Extrapolation Procedures, and Applications to the Third-Group Hydrides
Authors: Ginter Marshall L. , Battino Rubin
Published: January 2005

Uncertainties in potential curves determined by the Rydberg—Klein—Rees (RKR) method which result from approximations inherent in current applications of the method and from experimental errors are discussed. The use of the RKR method to extrapolate potential curves beyond the region known spectroscopically is discussed, with calculations on the X 1Σg+ state of H2 presented as examples. Application is made to the X 1Σ+ and a 3II states of GaH, InH, and TlH, with particular emphasis on the correlation of states from the lower MO configurations with the states of the separated atoms.
Higher-Order Stationary-Phase Approximations in Semiclassical Scattering
Authors: Smith Francis J. , Mason E. A. , Vanderslice J. T.
Published: January 2005

Higher-order stationary-phase approximations are used to calculate corrections to the classical expression for the differential cross section for elastic scattering. An expansion for the cross section as a series in ℏ2 is obtained, whose first term is the classical result. An oscillating term is also present, whose ``wavelength'' is approximately Δθ≈2π/kb. Both the ``wavelength'' and the amplitude of this term vary as ℏ. It is shown that the classical differential cross section is valid for angles as small as the critical angle defined by Massey and Mohr.

A similar technique is used to obtain corrections to Ford and Wheeler's semiclassical expression for the differential cross section at a rainbow angle. An expansion as a series in ℏ⅔ is derived, whose first term varies as ℏ—⅓ and hence diverges in the classical limit. It is shown that the leading term agrees with Ford and Wheeler's result and that the first correction term is very small for a 12–6 potential.
Mechanisms of Surface Recombination from Step-Function Flows of Atomic Oxygen over Noble Metals
Authors: Myerson A. L.
Published: January 2005

Surface recombination on four noble metals and titanium dioxide has been studied in flows containing a step-function increase in oxygen atom concentration. This has geen accomplished by means of thin-film heat-transfer techniques using catalytic and noncatalytic films. It is shown that silver, gold, platinum, palladium, and titanium dioxide all have the same small, but significant, catalytic efficiency during the first 50 or so msec of their initial exposire to atomic oxygen but that oxides are quickly formed on the metal surfaces which determine the catalytic ability during succeeding exposure. In some cases, these oxides are unstable and quickly converted to other oxides of different catalytic efficiency which determine the final catalytic properties of the metal. It is also shown that the better recombination catalysts are those for which the average metal—oxygen bond energies of the oxides are weaker.
On Detailed Balancing and Statistical Theories of Chemical Kinetics
Authors: Pechukas Philip , Light John C.
Published: January 2005

This paper amends a recent statistical theory of rearrangement collisions to bring it into accord with the detailed-balance theorem. Both classical and quantum formulations are discussed. The energy dependence of the cross sections near threshold and approximate formulas for the cross sections at arbitrary energies are derived.
Projection Operators in Quantum-Mechanical Perturbation Theory
Authors: Salzman W. R. , Baur M. E.
Published: January 2005

The construction of operator functionals of the full Hamiltonian of a quantum-mechanical system which act as projection operators for a specified exact eigenstate is studied. In general these operator functionals are not equivalent to the formal operator |ψ〉〈ψ|, where |ψ〉 is the state of interest, and are not always idempotent. A formal method by which standard perturbation theoretic expansions for the exact ground-state vector and ground-state energy of the system can be recovered by expansion of a certain operator functional of this type is presented. Related work is briefly discussed.
Trace Ferromagnetism in Zeolites
Authors: Singer L. S. , Stamires D. N.
Published: January 2005

Broad, intense electron resonance signals have been observed in heat-treated synthetic zeolites. Static susceptibility and high-temperature resonance measurements prove that the signals are ferromagnetic resonances. The observed Curie temperature of about 570°C strongly suggests that, during activation, ferromagnetic Fe3O4 is formed from trace amounts of ionic impurities present in the zeolitic starting materials.
Molecular Distributions at Equilibrium. IV. The New Family of Poly(chloroarsenous Methylimides)
Authors: Van Wazer John R. , Moedritzer Kurt , Rausch Marvin D.
Published: January 2005

Dissolution of the various amounts of the cage compound, As4(NCH3)6, in arsenic trichloride gives homogeneous liquids, the proton nuclear magnetic resonance (NMR) spectra of which show three major peaks. These resonances are attributed to methylimino bridges in (1) a pair of monofunctional units, (2) a pair consisting of a monofunctional and a difunctional unit, and (3) a pair of difunctional units where a unit of functionality i is part of a molecule and has the structure AsCl3—i[N(CH3)—]i/2. Large deviations from random scrambling of these structure-building units with respect to the formation in a ring-free system of the molecule consisting of two monofunctional units bonded together is interpreted primarily in terms of the presence of ring molecules.
Atomic-Beam Measurements of van der Waals Forces
Authors: Rothe Erhard W. , Neynaber R. H.
Published: January 2005

It is expected that the strength of the van der Waals potential (—C/r6 term) may be calculated from measurements of the total scattering cross section Q if the collision is of sufficiently low energy. Unfortunately, experimental values obtained for C have been about a factor of 2 higher than those predicted by theory. This discrepancy would be resolved if experimental Q's were about 30% lower. This paper discusses a systematic experimental error which may account for the high values for Q. This error is the Ishii—Nakayama pumping effect, which occurs in the normal use of McLeod gauges. We have eliminated this error in measurements of Q for scattering metastable helium and neon in rare gases. The resulting C's, and corrected C's for previously published alkali scattering, no longer include the factor of 2 discrepancy. Comparisons are made with other experiments.
Velocity Dependence of the Total Cross Section for the Scattering of Metastable He(3S1) by Helium, Argon, and Krypton
Authors: Rothe Erhard W. , Neynaber R. H. , Trujillo S. M.
Published: January 2005

The velocity (v) dependence of the total cross section (Q) has been measured for the scattering of helium in the metastable 2 3S1 state by ground-state helium, argon, and krypton at relative velocities in the range 1000–3300 m/sec. The results are compared with those previously obtained for the scattering of lithium. For each scattering gas, the shape of Q(v) is similar to that of lithium, but the absolute values for Q are approximately 20% higher. The scattering is largely elastic. It is estimated that the inelastic contribution to Q is about 10% for the He*–He case, and that it is less than 3% for the He*–Ar and He*–Kr cases. The Q(v) for scattering by argon and krypton show undulatory behavior. From the extrema velocities, the product εσ is shown to be close to that for Li scattering, where ε is the depth of the interatomic potential well and σ is the interatomic separation at the zero of the potential. The separate parameters ε and σ are also deduced. A minimum to the number of diatom bound states is established for HeAr(3Σ+) and HeKr(3Σ+).
Radiolysis of Binary Paraffin—Olefin Solutions. Cyclopentene and Cyclohexene in Cyclopentane and Cyclohexane
Authors: Yang John Y. , Marcus Inge
Published: January 2005

Radiolyses of binary paraffin—olefin solutions consisting of cyclopentene and cyclohexene in cyclopentane and cyclohexane have been carried out. Through a complete analysis of the product distribution for each of the paraffin—olefin pairs at varying olefin concentrations, it is concluded that the nature of the solvent—solute interaction must consist of both hydrogen-atom scavenging and energy or charge transfer. Large yields of diolefinic dimers are observed even at olefin concentrations as low as 1%, and these yields are attributed largely to nonradical processes following preferential energy localization in the olefins. It is suggested that hydrogen-atom scavenging processes predominate at very low olefin content, but physical interaction becomes the more important factor as the olefin concentration is increased beyond about 1%.
Multiple Ionization in Neon, Argon, Krypton, and Xenon
Authors: Stuber Fred A.
Published: January 2005

The ionization probabilities of Ne, Ar, Kr, and Xe have been measured with electron energies up to 2000 eV. Ions with charge up to 5 for Ne, 6 for Ar, 8 for Kr, and 9 for Xe were observed, and their ionization potentials are reported here.
Electron Spin Resonance of RĊHCOR′ Radicals in X-Irradiated Ketone—Urea Inclusion Compounds
Authors: Griffith O. Hayes
Published: January 2005

Single crystals of six inclusion compounds formed between aliphatic ketones and urea were x irradiated at room temperature, and the free radicals produced were investigated by electron spin resonance. The six ketones investigated were 2-nonanone, 6-undecanone, 3-tetradecanone, 2-undecanone, 2-dodecanone, and 3-undecanone. The long-lived free radicals observed in all of these compounds (RCH2ĊHCOR′) are formed by the removal of one α proton from the parent ketone. The unpaired spin density in the 2p orbital adjacent to the carbonyl group is 0.81±0.08. A contour plot of the spin density as a function of the molecular orbital parameters is given. In qualitative agreement with the ESR results, the molecular orbital methods predict the position of maximum spin density to be adjacent to the carbonyl group.
Electric-Quadrupole and Magnetic-Dipole Radiation in Linear Molecules. Applications to 1Π—3Π Transitions
Authors: Chiu Ying-Nan
Published: January 2005

The electric-quadrupole and magnetic-dipole operators of a rotating, linear molecule interacting with a radiation field are formulated, in the space-fixed and in the molecular-coordinate systems, as contractions of irreducible spherical tensors. Radiative transition probabilities are obtained for the initial and final rotation-electronic states that are in Hund's Coupling Case a or b, using the normalized rotation matrix as the separated rotational wavefunction in the Born—Oppenheimer approximation. Line-strength formulas are derived for (1) transitions between singlet Case b states, in the case of an electric quadrupole, the 1Σ—1Σ, 1Π—1Σ, 1Δ—1Σ, 1Π—1Π, 1Δ—1Π, 1Φ—1Π, 1Δ—1Δ, 1Φ—1Δ, and 1Γ—1Δ transitions; in the case of a magnetic dipole, the 1Π—1Σ, 1Π—1Π, 1Δ—1Π, 1Δ—1Δ, and 1Φ—1Δ transitions; (2) the 1Π—3Π(a) transitions; (3) the 1Π—3Π(b) transitions. The master line-strength formula as well as intensity distribution for different branches are given. In (2) and (3), some of the transitions are found to be dependent on the absolute Kronig reflection symmetry, giving, for molecules of unequal nuclei, an intensity alternation for the two Λ-doubling components. A discussion of this reflection symmetry and the inversion symmetry is given and a consistent set of molecular wavefunctions of a given symmetry is constructed for (1) singlet Case b states and triplet Case a states (2) triplet Case b states expressed as a linear combination of Case a state wavefunctions through angular momentum coupling. The rotation—vibration spectra due to these higher multipole radiations are briefly discussed. A new point of view for the possibility of ΔΛ=0 (for Λ≠0) magnetic-dipole pure rotation spectra is advanced.
Electron-Diffraction Study of the Structures of C2H4 and C2D4
Authors: Bartell L. S. , Roth E. A. , Hollowell C. D. , Kuchitsu Kozo , Young J. E.
Published: January 2005

The structures of ethylene and deuteroethylene were investigated by electron diffraction to resolve apparent discrepancies between earlier diffraction and spectroscopic studies. Satisfactory agreement with the previous diffraction study was found for five of the six molecular parameters determined but a difference of five standard deviations was encountered for the C–H bond length. Mean bond lengths and standard errors for C2H4 obtained in the present investigation were rg(CH)=1.1030±0.0018 Å and rg(CC)=1.3369±0.0016 Å. Corresponding lengths for C2D4 were rg(CD)=1.099±0.003 Å and rg(CC)=1.338±0.003 Å. Bond angles, corrected for shrinkage effects, were ∠CCH=121.4±0.6° and ∠CCD=121.4±0.8°. The new diffraction results are compared with mean bond lengths and angles calculated from spectroscopic rotational constants taking rotation—vibration interactions into account. Excellent agreement is found. Significant differences exist, however, between the conventional bond-length parameters derived by spectroscopy and diffraction. Root-mean-square amplitudes of vibration were also determined by diffraction, and these agreed satisfactorily with amplitudes calculated from vibrational frequencies.
Interaction Potential between He and H2
Authors: Krauss M. , Mies F. H.
Published: January 2005

The interaction potential of He with H2 has been determined in the Hartree—Fock approximation. An analytic expression for the interaction potential has been determined in a form suitable for consideration of energy-transfer problems. The expression is V(X, R, θ)=C exp{-α0X+α1Xr} {A(θ)+B(θ)r}, which is valid for 0≤R≤2 a.u., 2.5≤X≤3.8 a.u., where R=r+Re, Re=1.4 a.u. and C=198.378 eV, α0=1.86176 a.u.−1, α1=0.3206 a.u.−2, A(θ)=1.10041 {1+0.18250 P2(cosθ)}, B(θ)=−0.52151 {1−0.27506 P2(cos(θ)} a.u.−1. X is the distance between the He and H2 centers of charge, R is the H2 bond distance, and XR cosθ=X·R. From this result we see that the force exerted on the oscillator is comparable for both a collision along the line of centers and one along the molecular bisector.
Critical Examination of Vibrational Energy-Transfer Theory
Authors: Mies Frederick H.
Published: January 2005

An accurate He–H2 interaction potential is used to test the validity of the potential that has been employed in energy transfer theory. It is found that a model based on the assumption of additive exponential potentials acting between atomic centers does not reproduce the forces, matrix elements, or transition probabilities derived from the exact potential. The cross section for vibrational excitation is critically dependent on the details of the intermolecular potential; it is particularly sensitive to small differences in the diagonal matrix elements of the interaction potential. The discrepancies that are found for the relatively simple He–H2 system raises serious concern about the general validity of the model potential, particularly in its dependence on the internal coordinate of the oscillator.
Spin Relaxation of Optically Oriented Potassium Vapor
Authors: Bernheim R. A. , Korte Margaret W.
Published: January 2005

The spin-disorientation cross section σ and coefficient of diffusion D0 of potassium vapor in a helium buffer gas have been obtained from a study of the variation of the potassium spin-relaxation time with pressure of the helium buffer gas in an optical pumping experiment. The values obtained were σ=1.1×10−25 cm2 and D0=1.2 cm2 sec−1 at 85°C. The variation of σ for sodium, potassium, and rubidium vapor in a helium buffer gas is found to be consistent with the spin-orbit mechanism for spin relaxation. An efficient method for collecting spin-relaxation data has been developed and is described.
On the Charge Distribution and Electron Affinity of the OH− Ion in LiOH
Authors: Campbell I. D. , Coogan C. K.
Published: January 2005

The value previously published by Hon and Bray for the quadrupole splitting of the lithium resonance of LiOH powder has been used to deduce the electrostatic field gradient at the lithium site. Using a point-charge model, it is shown that the accepted structure (derived by Dachs using neutron-diffraction and x-ray techniques) leads to the two alternative, but plausible values −0.21e and +0.35e for the charge on the hydrogen atom of the hydroxyl ion. A calculation of the lattice energy for these two values of charge gives 232.5 and 282.9 kcal/mole, respectively. The accepted value is 233±1 kcal/mole, allowing us to decide in favor of −0.21e as the charge on the hydrogen atom. Other possible structures consistent with the crystal symmetry lead to unrealistic values of lattice energy. If allowance is made for the polarization energy of the hydroxyl ion in the LiOH lattice, we deduce an electron affinity of the ion of 46.5±4 kcal/mole.
Carbon-13 Chemical Shifts of the Carbonyl Group. III. Solvent Effects
Authors: Maciel Gary E. , Natterstad J. John
Published: January 2005

Carbon-13 chemical shifts were determined for the carbonyl groups of eight carbonyl compounds in a representative variety of polar, nonpolar, protic, and aprotic solvents. Simple ketones show a large sensitivity to environment if proton donors are present and small sensitivity to aprotic solvents. The relative sensitivities of the carbonyl compounds to solvent effects on the 13C=O chemical shift are: acetone, 1.05; pinacolone, 1.00; fenchone, 0.90; di-t-butyl ketone, 0.81; ethyl acetate, 0.51; methyl formate, 0.37; dimethyl carbonate, 0.15; hexachloroacetone, 0.03; probably reflecting the effect of a reduction in carbonyl basicity by the electron-withdrawing substituents OCH3, OCH2CH3, and CCl3. These results are interpreted in terms of carbonyl pi-bond polarity as influenced by hydrogen-bonding, polar and van der Waals interactions with solvent, the first being most important in protic solvents. The possible use of dimethyl carbonate as a solvent and internal reference is discussed.
Formation of H3+ and H5+ Ions
Authors: Saporoschenko M.
Published: January 2005

H+, H2+, H3+, and H5+ ions have been identified in hydrogen gas by use of a mass spectrometer with the ion source in the pressure range from 10−3 to 0.5 mm Hg. Secondary ions are formed in steps of consecutive reactions between ions and hydrogen molecules. Reaction cross sections of the secondary H3+ ions have been determined from the concentration dependence of the intensities of the H2+ ions. The tertiary H5+ ion is formed in three-body collisions of the H3+ ion with the hydrogen molecules. Dissociation processes of all three molecular ions have been observed.
Mass-Spectrometric Study of the Sublimation of MnS(s) and the Dissociation Energy of MnS(g)
Authors: Wiedemeier Heribert , Gilles Paul W.
Published: January 2005

Mass-spectrometric measurements on stoichiometric MnS and a mixture of MnS and graphite in tungsten crucibles show that the former vaporizes congruently to produce Mn(g) and ½S2(g) and that the latter system reacts to form Mn(g) and CS(g). Small quantities of MnS+, MnS2+, MnS3+, sulfur polymers, and possibly Mn2+ and Mn3+ were also observed. Intensity measurements on Mn+, S+, S2+, and MnS+ and previously measured decomposition pressures of MnS were combined in a third-law treatment to yield for the dissociation energy of MnS(g) 71±4 kcal/mole. The associated heat of formation from solid elements is 67±6 kcal/mole. The thermodynamic results are given in Eqs. (4) to (9). Very approximate values of energies for dissociation of a sulfur atom from MnS2 and MnS3 are given.
Nature of the Chemical Reactivity of Radiobromine Atoms Produced by Isomeric Transition
Authors: Kazanjian A. R. , Libby W. F.
Published: January 2005

The hot-atom chemistry of n-propyl bromide has been examined further. By comparing the differences and similarities of the (n, γ) and isomeric transition processes, an over-all theory is evolved which accounts for the identical results produced by both nuclear processes in the solid and liquid alkyl halides. The charge developed by the Auger process following internal conversion causes the molecule to explode and gives a neutral recoiling atom which then reacts as the (n, γ) atoms. The neutralization after rupture is rapid in the solid and liquid. In the gas this is not so and it has been possible to demonstrate experimentally a difference between the retentions in the gas phase.
Correlation Energy in Atomic Systems. III. Configurations with 3d and 4s Electrons
Authors: Clementi E.
Published: January 2005

The correlation energy for systems containing 3d and 4s electrons has been examined making use of recently obtained Hartree-Fock energies for the elements from K to Zn. In addition to the expected pair correlation between 3d electrons, a large extrashell correlation has been found. These results make it desirable to re-examine the simple correlation model previously put forward. The relativistic correction for the elements in consideration has been discussed.
Effect of Collision Partners on Vibrational Relaxation
Authors: Boade R. R.
Published: January 2005

The Schwartz, Slawsky, and Herzfeld theory is applied to some previously reported data on substituted methane-inert-gas mixtures. It is found that the vibrational relaxation process can be quite adequately explained with this theory and a knowledge of intermolecular force constants. It is also shown that the linear relationship between log(τAB) and μ½, which apparently holds for diatomic dispersive gases, breaks down for more complicated molecules.
Lower Bounds for the Eigenvalues of First-Order Density Matrices
Authors: Kutzelnigg Werner , Smith Vedene H.
Published: January 2005

Lower bounds for the first n eigenvalues of the first-order density matrix corresponding to a quantum-mechanical state of an n-electron system are derived under the three assumptions: (1) that one knows a lower bound to the overlap integral of an arbitrary normalized Slater determinant with the true wavefunction. (2) that the configuration interaction expansion of the true wavefunction contains only singly, doubly, etc., up to m-fold excited configurations with respect to a ``ground'' configuration, where m≤n. (3) That the electronic-interaction term in the Hamiltonian is proportional to a parameter λ and that a perturbation expansion in terms of this parameter is possible. In the latter case one finds that the idempotency of the one-particle density matrix is stable with respect to first-order perturbations.