bluuebunny/crossref_metadata_2025 huggingface dataset:
Wavefunctions and Binding Energies of the Titanium Monoxide Molecule
Authors: Carlson K. Douglas , Nesbet R. K.
Published: January 2005

Approximate wavefunctions for the low-lying 1Σ+ state of the titanium monoxide molecule have been calculated by the method of Roothaan at three internuclear distances about the minimum of the potential energy curve. Basis orbitals were chosen to represent the principal effects of distortion and polarization of the atomic constituents for a very limited set of atomic basis orbitals. The calculations yield approximate Hartree—Fock molecular constants and binding energies for the 1Σ+ state, and for the 3Δ ground state and other excited states relative to the 1Σ+ state. An empirical estimate of the net molecular correlation energy relative to separated atoms is made using purely atomic data for appropriate ionic constituents of the molecule. The computed dissociation energies are in qualitative agreement with experimental values but have small errors partly owing to the approximations employed in the calculations. The ground-state parameters obtained here are De=5.61 eV, Re=1.539 Å, ωe=1263 cm—1, compared with experimental values De=6.86±0.30 eV, Re=1.620 Å, ωe=1008.4 cm—1.
Molecular Schrödinger Equation. I. One-Electron Solutions
Authors: Conroy Harold
Published: January 2005

A general form for the wavefunction of a single bound electron moving in the field of arbitrary fixed nuclei is proposed. The use of this wavefunction in the molecular Schrödinger equation results in the exact cancellation of singularities due to the electron—nuclear attractive potential. Illustrations of its application to the first few states of the hydrogen molecule—ion (H2+) as well as information about accuracy and convergence rate are presented.
Vibrational Spectra of the Ices. Raman Spectra of Ice VI and Ice VII
Authors: Marckmann J. P. , Whalley E.
Published: January 2005

The Raman spectra at 77°K and atmospheric pressure of Ices VI and VII made from both H2O and D2O have been obtained in the O–H and O—D stretching regions using Hg 4047-Å and Hg 4358-Å radiation. Ice VI has only one band, and this band is slightly higher in frequency than the corresponding band of Ices II, III, and V. It seems likely from this that Ice VI is still fully hydrogen bonded and essentially four coordinated. Ice VII has three bands, and all are shifted considerably from the bands of Ices I, II, III, V, and VI towards the vapor frequencies. It seems likely that the hydrogen bonding has been altered from that of Ice I more profoundly in Ice VII than in Ices II, III, V, and VI, but that strong hydrogen bonds are still present.
Far-Ir Spectrum of Dimethylacetylene: Internal Rotation and Evidence for a D6h Effective Symmetry
Authors: Kopelman Raoul
Published: January 2005

The spectrum of dimethylacetylene vapor, liquid, and solid phases has been measured in the region 50 to 450 cm—1. Therefrom, together with previous work, a unique and ``complete'' vibrational assignment is derived. Rotational fine structure seems to confirm ``free internal rotation,'' i.e., a barrier below 100 cal/mole.

Dimethylacetylene is an ethane-type molecule with practically free internal rotation. The new data strongly confirm the previous conclusion that neither D3, D3h, or D3d are appropriate symmetry groups. The selection rules are consistent with a D6h effective symmetry.

An appendix deals with the relative intensities in degenerate vibrational transitions.
Molecular Motion and the Moment Analysis of Molecular Spectra. III. Infrared Spectra
Authors: Gordon R. G.
Published: January 2005

The shapes of infrared rotation—vibration bands are analyzed theoretically in terms of their moments. The third and fourth moments of a band are found to increase when the molecular rotation is hindered, whereas the second moment is almost unchanged by the intermolecular torques. Explicit expressions are given for the third and fourth moments of interacting almost classical rigid asymmetric rotors, in terms of functions of the intermolecular torques, the temperature, the principal moments of inertia and the polarization direction of the transition. For the special case of a diatomic molecule or a parallel transition in a linear molecule, the theory is refined to include the first-order quantum corrections, the rotation—vibration interaction, and the effects of frequency shifts. The analysis is applied to available infrared spectra of carbon monoxide in gaseous, liquid, and solid pure phases and mixtures. Values of the mean-squared torque on the CO molecule are derived from the experimental data. It is found that the rotational motion of CO is strongly hindered in the solid, liquid, and highly compressed gas.

The mean-squared torque in gaseous CO and CO–Ar mixtures increases linearly with the density until densities close to those of the liquid. Therefore the intermolecular torques between CO–CO and CO–Ar must be of very short range. Sufficient data are available so that some tests of the consistency of this interpretation may be made.
Temperature Dependence of Pure Nuclear Quadrupole Spin—Lattice Relaxation in SnI4
Authors: Daniel Alfred C. , Moulton W. G.
Published: January 2005

The pure nuclear quadrupole spin—lattice relaxation times for 127I in SnI4 have been measured over the temperature range from 4.2° to 300°K. Measurements were performed on both the 208- and 416-Mc/sec transitions. From the solution of the rate equations the transition probabilities, W1 and W2, corresponding to Δm=±1 and Δm=±2 transitions, are evaluated using the experimentally determined relaxation times. The ratio of the two required relaxation times is found to have a rather insensitive dependence upon W2/W1 and could be determined only at temperatures below 77°K. For temperatures below about 15°K a third relaxation time was required to describe the observed relaxation curves. Since cross-relaxation or spin—diffusion effects were not observed, the determination of the spin—lattice relaxation times from the stimulated echo was found to give far more accurate results than the conventional two-pulse technique.

The theory of quadrupolar relaxation developed by Bayer and the modification given by Woessner and Gutowsky have been reformulated for nuclei with spin 53. The third time constant required to fit the low-temperature data is predicted by either theory even though the details of the theory do not agree well with experiment results. The ratio W2/W1 is found from the experimental observations to increase by a factor of about 2 as the temperature decreases from 77° to about 7°K. The results obtained from Bayer and from Woessner and Gutowsky indicate an opposite effect. However, by assuming a temperature dependence for the molecular vibrational frequencies, better agreement can be obtained between the expressions for W2/W1 and the experimentally determined values. The temperature dependence of the lifetime of the molecular torsional oscillations has not been determined in detail and remains as a second parameter of poor definition. Because of the limited information describing the molecular torsional oscillations, relatively poor agreement is obtained between the theoretical and experimental determinations of the individual W1 and W2 transitions.
Dissociation Energies of Diatomic Molecules of the Transition Elements. I. Nickel
Authors: Kant Arthur
Published: January 2005

The Ni2 molecule has been shown to exist in the vapor phase over liquid nickel above 2000°K.

Using information derived from a combination of effusion and mass-spectrometric techniques, the dissociation energy of Ni2 has been calculated from the ratio of dimeric and monomeric nickel in equilibrium with liquid: D00(Ni) = 54.5±5 kcal.

From the accepted value of the heat of sublimation of nickel and the dissociation energy of the dimer the heat of sublimation for the process 2Ni(solid) = Ni2(gas) is, at 0°K, 146.9±7 kcal.
Coriolis Shifts in Elastic Scattering Potentials
Authors: Thorson Walter R. , Bandrauk Andrew D.
Published: January 2005

Nonadiabatic effects (Coriolis shifts) have been studied in the 2Σu+ and 2Σg+ states of H2+, for elastic scattering at high relative kinetic energies. This study was made to explore the effects in a simplest prototype system; conclusions are also qualitatively applicable to the He2 system, for which earlier and incomplete studies were made by W. R. Thorson. The phenomenon is relevant to the existing large discrepancy between adiabatic theoretical calculations and the results of high-energy scattering experiments determining the interaction potential in He2. The results of the study are useful in a study of the scattering proper in the H2+ system.
Raman Spectrum of Polycrystalline Methyl Bromide
Authors: Ito Mitsuo
Published: January 2005

The Raman spectrum of polycrystalline methyl bromide has been observed at 77°K. Two Raman bands at 585 and 594 cm—1 of ν3 were characteristic of rapidly cooled samples. The band at 585 cm—1 disappeared from samples slowly cooled or subjected to warming and cooling several times. The origin of the 585-cm—1 band is discussed and ascribed to the supercooled crystal or to the amorphous solid. Only the intramolecular fundamental ν5 has been observed to split due to the crystal field.

Four lattice vibrational frequencies have been obtained and their tentative assignments are presented.
Approximate Hartree—Fock Wavefunction for the Helium Atom
Authors: Zung Joseph T. , Parr Robert G.
Published: January 2005

The function φ=Aexp(−ζr)+B(1/ζ′′r)exp(−ζ′r)[1−exp(−ζ′′r)] is shown to be an excellent analytical approximation to the Hartree—Fock orbital of the helium atom, giving an energy of —2.86167 a.u., versus the exact Hartree—Fock energy —2.86168 a.u. Differences between this and other approximate orbitals, and the exact Hartree—Fock orbital, are discussed. The orbital form due to Green is recovered as the special case ξ″=0. It also yields the energy —2.86167 a.u., but it gives less accurate values for 〈r〉, 〈r2〉, 〈r3〉, and 〈r4〉 than are given by the generalized form. Reasons are given for including, in atomic and molecular variational calculations as new s-type orbitals, functions of the form, 0s=[exp(−αr)−exp(−βr)]/r.
Gross- and Partial-Ionization Cross Sections for Electrons on Water Vapor in the Energy Range 0.1–20 keV
Authors: Schutten J. , de Heer F. J. , Moustafa H. R. , Boerboom A. J. H. , Kistemaker J.
Published: January 2005

Measurements have been made on the gross-ionization cross sections for 0.1–20-keV electrons on water vapor at pressures of about 3×10−4 torr. The results are compared with the cross sections of H2 and O2. Within the experimental error of 15% we found no deviations from the additivity rule. The energy dependence of the cross section satisfies the Bethe—Fano—Platzman relation for collision-induced dipole transitions at energies exceeding 400 eV. A comparison is made with photoionization and inelastic electron-scattering cross sections. Some results are given on the partial cross sections for the production of fragment ions for 0.02–2-keV electrons on water vapor.
Infrared Spectrum and Vibrational Potential Function of Hydrazoic Acid
Authors: Moore C. Bradley , Rosengren Kjell
Published: January 2005

Gas-phase and N2 matrix vibrational spectra of HN3, DN3, H15NNN, 15NNNH, D15NNN, and 15NNND are reported. The pure rotation spectrum of HN3 is given as well. Strong vibration—rotation interaction is evident in the v5, v6 spectra, in the changes of the A rotational constant by 4%−8% in the hydrogen stretching and bending fundamentals, and in the pure rotation spectrum of HN3. Normal coordinates and eight force constants are determined using 22 vibrational frequencies from six molecules. A large (HNN bend)—(HN–N stretch) interaction force constant is found. Its magnitude and sign are readily understood in terms of the electronic structure of hydrazoic acid.
Electronic Absorption Spectra of the Gaseous 3d Transition-Metal Dichlorides
Authors: DeKock C. W. , Gruen D. M.
Published: January 2005

Electronic absorption spectra of gaseous VCl2, CrCl2, FeCl2, CoCl2, NiCl2, and CuCl2 have been measured near 1000°C and in the range 4000–50 000 cm−1. With the exception of VCl2, extensive vibronic structure was observed in the spectra of these molecules. The spectra are characterized by low intensity (ε=10–120 liter/mole·cm) dn←dn transitions in the 4000–22 000-cm−1 region and by higher intensity (ε=2500–24 000 liter/mole·cm), transitions in the 19 000–50 000-cm−1 region.

The dn←dn transitions are reasonably well fitted by A2=±900 cm−1, A4=±100 cm−1, the two ligand-field parameters appropriate for a molecule of symmetry D∞h. The narrow band (half-width ∼120 cm−1) at 11 727 cm−1 in NiCl2 is assigned to a 1Σ(1D)←3π(3F) transition.
Absorption Spectrum of SF6 in the Far Ultraviolet by Electron Impact
Authors: Simpson J. Arol , Kuyatt C. E. , Mielczarek S. R.
Published: January 2005

Measurements of forward inelastic scattering of 400-eV electrons from SF6 were made and used to derive relative ultraviolet-absorption cross sections. The relative values were normalized to an ultraviolet-absorption measurement at 23.00 eV. Agreement with additional uv measurements at 21.2 and 17.6 eV was excellent. Oscillator strengths for three absorption bands between 10 and 15 eV, as derived from the electron-scattering measurements, are in fair agreement with the corresponding values measured by uv absorption. The total oscillator strength for excitations up to 32 eV is found to be 15.3.
Paramagnetic Resonance Study of Liquids during Photolysis: Hydrogen Peroxide and Alcohols
Authors: Livingston Ralph , Zeldes Henry
Published: January 2005

Paramagnetic resonance spectra of free radicals in liquids have been studied during the course of intense irradiation with ultraviolet light. Equipment is described in which the liquid sample flows through the microwave cavity of the spectrometer and is photolyzed as it passes the sensitive region of the cavity. In this way the steady-state concentration of short-lived radicals have been observed. Temperatures from about −70° to 60°C have been used. A number of alcohols containing up to 1% H2O2 have been studied. In the absence of dissolved oxygen the main products are the radicals formed by abstraction of a hydrogen from the position alpha to the hydroxyl group. The radicals RĊHOH where R is H, CH3, C2H5, C3H7, (CH3)2CH, and C6H5 have values of aα near room temperature ranging from 14.7 to 17.4 G and g values ranging from 2.00298 to 2.00334. Those radicals with beta hydrogens have values of aβ ranging from 20.0 to 22.2 G. The ring protons of C6H5ĊHOH are inequivalent. When the alpha hydrogen is abstracted from allyl alcohol two radicals are formed that are geometric isomers with the relative abundances depending on temperature. Coupling values for all hydrogens in each isomer are given. All couplings are also given for the radicals formed from ethylene glycol and isopropyl alcohol. In many cases couplings have been measured at several temperatures. Values for hydrogens in hydroxyl groups are strongly temperature dependent and in some cases become zero. Alpha and beta coupling constants are less temperature dependent. The various results are discussed. In the presence of dissolved oxygen, peroxy radicals are formed and their spectra are discussed. Their linewidths are strongly dependent on temperature and on concentration of dissolved oxygen. Radicals have been seen in photolyzed hydrogen peroxide solutions for concentrations ranging from 10% to 45%. In the presence of acid a single absorption line is observed. Without the acid the spectra are complex. These results are also discussed.
Physical-Cluster Theory for a Reactive Gas
Authors: Lawson Craig , Dahler John S.
Published: January 2005

Physical-cluster expansions are given for the thermodynamic properties and equation of state of a reactive fluid. This provides a statistical-mechanical characterization of the fluid in terms of the stable atomic aggregates or molecules which actually are present rather than in terms of the more familiar, but less intuitive, Ursell—Mayer cluster integrals. Here, the Ursell—Mayer cluster development is applied only to the molecular interactions and not to the stronger ``chemical'' forces which are responsible for the stability of these aggregates. Detailed attention is given to a system composed exclusively of monomers and dimers. Formulas are derived for all of the coefficients needed to determine the first-order density corrections to the equation of state and composition of the fluid. Numerical results are reported for the special case of a square-well atom—atom interaction and a nonadditive three-body potential which is rigid and repulsive. Finally, we present a more general, quantum-mechanical version of the theory.
Nonstationary Contributions to the Bulk Viscosity and Other Transport Coefficients
Authors: Nicolis G. , Severne G.
Published: January 2005

The nonstationary contributions to the transport coefficients, i.e., those associated with the term ∂f/∂t in the kinetic equations, are analyzed within the framework of the Prigogine theory. These contributions, which more especially concern the bulk-viscosity coefficient, are shown to combine with the stationary contributions to yield a result equivalent to that provided by autocorrelation function theory; this completes Résibois' proof of the equivalence of the kinetic and autocorrelation function methods. The connection with the finite frequency approach is also established. Finally, some comments are made on the definition of temperature in nonequilibrium systems, a matter which is in direct connection with the evaluation of the bulk-viscosity coefficient.
Effect of Hydrostatic Pressure on Molecular Rotation in Solids
Authors: Anderson J. E. , Slichter W. P.
Published: January 2005

Measurements of the NMR spin—lattice relaxation time T1 have been carried out at various temperatures and pressures for eight solids that demonstrate rotational degrees of freedom. Apparatus is described which permits NMR pulse experiments to be performed over the temperature interval between 169° and 400°K under applied hydrostatic pressures between 1 and 680 atm. The intramolecular rotation of groups within molecules is insensitive to pressures within this range, and the rotation of entire molecules in the solid state is pressure dependent in varying degrees. The observed pressure coefficients of T1 in these solids are related to the thermal expansion coefficient of the lattice by a simple model that postulates a localized lattice expansion as an important step in the reorientation process.
Some Potential-Energy Surfaces on H3+ Computed with Generalized Gaussian Orbitals
Authors: Pearson A. G. , Poshusta R. D. , Browne J. C.
Published: January 2005

With an 18-term wavefunction, using 16 generalized Gaussian orbitals as a basis, we find a minimum energy of −1.3185 a.u. for H3+ in an equilateral triangular configuration having sides 1.66 bohr The A1′ normal mode of vibration has ω0=3610 cm−1. Several energy contours are presented and their relation to H2+D+→HD+H+ reactions is sketched.
Perturbation Theory of the Intrinsic Viscosity of Polymer Chains
Authors: Pyun Chong Wha , Fixman Marshall
Published: January 2005

Our previous calculation of the intrinsic viscosity [η] of linear flexible polymer chains is improved by the inclusion of interactions between excitations, which interactions arise mainly from fluctuations in the hydrodynamic interaction tensor. In the equation [η]=φ×1023L3/M (where L in the root-mean-square end-to-end distance and M in the molecular weight; cgs units), φ was found to equal 2.68 in the previous zeroth order approximation. In first-order perturbation theory φ decreases to 1.81, and in second order φ rises in excess of 2.66. An approximate summation to infinite order of the interaction responsible for the large decrease in first order, and other considerations are adduced in support of the view that the remaining terms of the perturbation series are relatively small.
Infrared Spectra of Charge-Transfer Complexes. VI. Theory
Authors: Friedrich H. Bruce , Person Willis B.
Published: January 2005

The general theory of molecular vibrational transition intensities is discussed with emphasis on electronic reorientation contributions to the intensities. The wavefunctions used by Mulliken to represent the electronic states of donor—acceptor complexes are written to include an explicit dependence on the vibrational coordinates. These functions and the general theory are applied to the intensities of halogen vibrations in donor—acceptor complexes. Specific application to actual complexes requires the estimation of the derivative of the vertical electron affinity of the halogen molecule with respect to its internuclear distance, the electronic transition moment of the charge-transfer band, the coefficients in the donor—acceptor ground-state wavefunctions and the difference between the energies of the dative- and no-bond states. Evaluation of each of these parameters is discussed for a number of complexes of halogens and relationships between the wavefunction coefficients and the infrared frequency shifts are described. The calculations indicate that all of the intensity enhancement of the halogen—halogen stretching vibration may be due to electronic reorientation during the vibration. Partly as a result of this conclusion, it is argued that no information about the geometry of the benzene—halogen complexes may be deduced form the infrared spectrum, at least in any simple way. The argument is extended qualitatively to hydrogen-bonded systems to indicate the probable similarity in explanation for the enhancement of the X—H stretching vibrations. In conclusion, a number of generalizations are presented regarding the spectra of complexes.
Polyhedral Clathrate Hydrates. XI. Structure of Tetramethylammonium Hydroxide Pentahydrate
Authors: McMullan R. K. , Mak T. C. W. , Jeffrey G. A.
Published: January 2005

The crystal structure of tetramethylammonium hydroxide pentahydrate has been determined at 25°C by an analysis of the three-dimensional x-ray-diffraction data. The unit cell is orthorhombic with a=12.57, b=10.96, c=7.91 Å and contains four formula units. The OH− ions and H2O molecules form a hydrogen-bonded framework based on the space-filling arrangement of truncated octahedra. Equivalent (CH3)4N+ ions occupy the four available polyhedral cages in the unit cell and distort the cubic symmetry of the idealized oxygen lattice formed from undistorted face-sharing truncated octahedra. Three carbon atoms of each cation are disordered giving rise to a circular distribution of electron density about the fourth N–C bond axis, which suggests that the cations are behaving as slightly hindered axial rotors. In the framework structure, the number of hydrogen-bonded edges equals the number of available protons, with ⅓ and ⅔ of the oxygen atoms forming 3 and 4 bonds, respectively. The framework of this hydrate resembles closely that found in the acid hydrate HPF6·6H2O. Although the clathration of the cationic guests is similar in principle to that in the tetra-n-butyl and tetraisoamyl ammonium salt hydrates, the structural geometry of the host lattice is quite different since it is derived from the truncated octahedron, instead of the pentagonal dodecahedron.
Molecular Ions in Radiation Chemistry. II. Aromatic-Hydrocarbon Cations in CCl4 at 77°K
Authors: Shida Tadamasa , Hamill William H.
Published: January 2005

Solutions of aromatic hydrocarbons in a polycrystalline matrix of CCl4 at 77°K have been γ irradiated and well-resolved optical absorption spectra measured in the interval 270–2000 mμ. All spectra characteristic of solute are attributed to molecular monopositive ions of benzene, toluene, bi- and triphenyl methanes, biphenyl, o-, m-, and p-terphenyl, bi-, tri-, and tetraphenylethylene, biphenylacetylene, naphthalene, anthracene, phenanthrene, stilbene, diphenylstibene, and 1,3,5-triphenylbenzene. Resonance charge transfer from CCl4+ to CCl4, terminated by transfer from CCl4+ to solute, is postulated.
Internal Rotation in Completely Asymmetric Molecules. II. Interactions between Vibration and Internal Rotation
Authors: Quade C. Richard
Published: January 2005

The theory of internal rotation for molecules with asymmetric internal rotors is extended to include the interactions of normal vibrations with the hindered internal rotation. The Sayvetz condition is derived for separation of internal rotation and vibration in zeroth order in the kinetic energy. Then the complete Hamiltonian is developed which includes the effect of the α dependence of the vibrational kinetic energy as well as those terms which are introduced through the reduction in symmetry of the vibrationally distorted molecule. An effective internal, over-all rotation Hamiltonian is isolated for the vth vibrational state by a Van Vleck transformation.

The behavior of various terms in the Hamiltonian are examined in detail in the case of molecules for which both the framework and top possess planes of symmetry. Particular attention is devoted to the use of symmetry properties in discussing the α dependent properties of the Hamiltonian. Perturbation theory is used to obtain an effective rotational Hamiltonian for the nth torsional state. It is found that the structure of some rotational transitions is sensitive to particular new terms which are introduced by vibration. The microwave spectra of CH2DCOH and CHD2COH are analyzed on a parametric basis.
Infrared Spectrum and Normal-Coordinate Analysis of SF4
Authors: Levin Ira W. , Berney Charles V.
Published: January 2005

The vibrational spectrum of sulfur tetrafluoride has been examined in the gas phase to 33 cm−1. A previous assignment of the fundamental vibrations has been revised. A normal-coordinate calculation, employing mean amplitudes of vibration as additional constraints to the vibrational problem, has been used to support the proposed assignment.
ESR of Cu(NO3)2 and CuF2 Molecules Oriented in Neon and Argon Matrices at 4°K
Authors: Kasai Paul H. , Whipple Earl B. , Weltner William
Published: January 2005

An experimental apparatus is described which allows the trapping of preferentially oriented molecules in neon and argon matrices at 4°K and the measurement of their ESR spectra at various orientations relative to the magnetic field. Application to Cu(NO3)2, vaporizing at 150°C, and CuF2, vaporizing at 925°C, demonstrates that the degree of orientation is dependent upon the temperature of the vaporizing molecule and the matrix gas used. The ESR spectra of highly oriented Cu(NO3)2 in neon at 4°K (there was essentially no orientation in argon) indicate that the molecule is planar with the four nitrate oxygen atoms surrounding the Cu++ ion in a square array. The g and A values are very similar to those found in copper chelate molecules: g∥ = 2.2489±0.003, g⊥ = 2.0522±0.0005, A∥ (63Cu) = 570±3 Mc/sec, and A⊥ (63Cu) = 50±3 Mc/sec. Computer simulation of the spectra not only confirms this assignment but provides an estimate of the degree of orientation as a function of the inclination. CuF2 isolated in argon at 4°K has been found to be highly oriented also. Its ESR assignment supports the view that the molecule is linear with magnetic parameters g∥ = 1.913±0.001, g⊥ = 2.601±0.001, A∥ (63Cu) = 1933±5 Mc/sec, A⊥ (63Cu) = 2090±5 Mc/sec, A∥ (F) = 308±1 Mc/sec, and A⊥ (F) = 206±1 Mc/sec. The unusually large hyperfine interaction with the Cu nucleus indicates a substantial admixture of its 4s orbital. For both molecules the assignments were greatly facilitated by the partial orientation of the molecules in the matrices. The optical spectra of CuF2 in neon at 4°K yielded the asymmetric stretching frequency at 769 cm−1. No absorption bands were found between 8900 and 3300 Å.
Oscillator Strengths of the First Negative and Second Positive Systems of Nitrogen
Authors: Jeunehomme M.
Published: January 2005

A fluorescence-lifetime-measuring technique which employs pulsed or modulated rf discharges is described. The method is applied to the emission of the second positive and first negative systems of nitrogen. Values of the lifetime of the upper states of both systems are given, and their variation with gas pressure and electron energy is discussed. Recommended values for the oscillator strengths are presented.
Nonadditivity of Intermolecular Forces: Effects on the Third Virial Coefficient
Authors: Sherwood A. E. , De Rocco Andrew G. , Mason E. A.
Published: January 2005

The effects of nonadditive three-body forces on the third virial coefficient C(T) are examined. Corrections to the dispersion and repulsion pair potentials are taken, respectively, from third-order perturbation theory without exchange (triple dipole) and from first-order perturbation theory with exchange. The repulsion is examined for two specialized models, a one-electron Gaussian model and an electrostatic distortion model. The results for the nonadditivity are shown to agree reasonably well with the quantum-mechanical results on one- and two-electron atoms. The magnitudes of the corrections to the repulsion and dispersion energies are comparable for the ranges of interatomic separations of interest. The correction to C(T) for repulsion nonadditivity is of opposite sign but comparable magnitude to that for dispersion nonadditivity in the temperature range of interest. The net correction, however, is of experimental significance and it is suggested that careful experiments near the maximum in C(T) would be useful. The net correction to C(T) is unfortunately sensitive to the choice of the pair-potential model, so that advances in knowledge of three-body forces from C(T) will probably depend on improvements first being made in knowledge of two-body forces.
Capillary Viscometry: Analysis of Kinetic Energy and Hydrostatic Head Corrections and a More Exact Calculation
Authors: Wellman R. E. , DeWitt R. , Ellis R. B.
Published: January 2005

An extensive experimental investigation and an analysis of previous results on capillary viscometry have resolved many of the contradictory results and conclusions concerning the constancy of the kinetic-energy correction factor, usually denoted m. This factor is shown to be constant within experimental error at flow rates corresponding to Reynolds numbers from 50 to 1500. The reported gross changes in m, as the Reynolds number is varied, are shown to derive from calculation errors and from neglect of certain established corrections. A more accurate calculation of the kinetic-energy correction term, to take into account the variation in flow rate within a single determination, is required if the calibration and test materials have greatly different kinematic viscosities.
Relativistic Intermolecular Forces, Moderately Long Range
Authors: Meath William J. , Hirschfelder Joseph O.
Published: January 2005

The generalized Breit—Pauli Hamiltonian is used to give a systematic treatment of magnetic and other relativistic intermolecular energies through O(α2) (where α is the fine-structure constant) for intermolecular separations, R, sufficiently large that the charge distributions of the two molecules do not overlap, but sufficiently small that R<λ/0=(αΔε)−1, where Δε is the excitation energy of the first allowed transition of one of the molecules.

The theory is discussed in general and many types of interaction energies are obtained which depend on the spin and orbital angular-momentum states of the molecules. The interaction of two nondegenerate atoms (L=0, S=0) is considered specifically. Of particular interest is an interaction-energy term which varies as α2/R4.
Infrared Spectra of HCl and DCl in Solid Rare Gases. I. Monomers
Authors: Keyser L. F. , Robinson G. W.
Published: January 2005

A low-temperature infrared cell capable of maintaining temperatures between 7° and 50°K is used for the study of the vibration—rotation spectra of HCl and DCl in solid rare gases. Spectra at 0.2% to 2% concentrations in solid krypton and xenon are obtained. Spectra in argon have already been reported by other workers. Fine structure in the region of the (1–0) vibrational transitions is assigned to monomeric and polymeric species of HCl and DCl. The polymer lines can be assigned to dimers and trimers. A detailed description of these interesting features will appear in Paper II of this series. The monomer lines are assigned to vibration—rotation transitions of HCl and DCl. In addition to a J-independent band-origin shift, the rotational levels of HCl exhibit J-dependent perturbations of 5 to 10 cm−1; the J-dependent perturbations of the DCl rotational levels lie between 1 and 3 cm−1. Neither hindered rotation nor libration of HCl and DCl in the rare-gas crystals provides a suitable description of these perturbations. A model suggested by Friedmann and Kimel based on the interaction of the rotational motion with the localized lattice vibrational (``translational'') motion of HCl and DCl at substitutional sites in the rare-gas crystals is used to interpret the J-dependent perturbations. A Hamiltonian, which treats the ``translational'' frequencies of HCl and DCl and the strength of the translation—rotation interaction as parameters, is constructed. The Hamiltonian matrix is truncated at a convenient size, and the perturbed energy levels are found by direct diagonalization of the truncated matrix. For a heteronuclear diatomic rotor in a cubic lattice, the translational—rotational states are shown to form a basis for the irreducible representations of a group isomorphous with D2h. This property allows considerable factorization of the Hamiltonian matrix. The values of the ``translational'' frequencies which give the best fit to the observed rotational spacings are 36 cm−1 in xenon, 57 cm−1 in krypton, and 31 cm−1 in argon. The model in the case of argon is likely to be fuzzy because of the near mass resonance between argon and HCl or DCl. The strength of the translation—rotation interaction as measured by the distance between the center of mass and the center of electrical symmetry in the molecule is 0.13 Å for HCl and 0.096 Å for DCl. A mechanism for the induction of a Q branch in the vibration—rotation spectra of monomeric HCl and DCl in the solid rare gases is discussed in Paper III of this series.
Chemisorption of Electronegative Gases on Refractory Metals
Authors: Shaw Marion L. , Carleton N. P.
Published: January 2005

This experiment is a study of some aspects of the chemisorption of diatomic gases on metal surfaces for temperatures of 1800°—2200°K and pressures of 4.0–6.0×10−6 torr. The systems studied were chlorine and carbon on tungsten where the carbon was present as a contaminant, and chlorine and hydrogen chloride on hafnium. We observed the flux of atomic negative ions formed from the dissociated gases on the surfaces as functions of temperature concurrently with the thermionic electron flux from the same surfaces. From these data we calculated work functions and sticking probabilities, using the Saha—Langmuir equation. For tungsten, we find that the sticking probability of chlorine was about 4×10−3 and tended to decrease with increase in temperature. The increment in work function was about the order of the experimental uncertainty, 0.50 eV. For hafnium the sticking probability was about 1×10−2 for both chlorine and hydrogen chloride and tended to increase with temperature, especially in the presence of oxygen at a partial pressure of 5×10−6 torr. This temperature dependence we have interpreted as an indication of a contaminated surface. The work function was not noticeably changed by chlorine or hydrogen chloride. Introduction of oxygen into the system caused the work function to increase noticeably.
Nuclear Magnetic Resonance Study of Molecular Motions in Solid Hydrogen Sulfide
Authors: Look D. C. , Lowe I. J. , Northby J. A.
Published: January 2005

Pulsed nuclear magnetic resonance experiments on protons in solid hydrogen sulfide have been carried out at 10 Mc/sec over the temperature range of 4.2° to 175°K. Proton spin—lattice relaxation times T1 and T1r along the static and rotating magnetic fields, respectively, and free-induction-decay shapes were measured. The T1r-vs-reciprocal-temperature curves exhibit several minima which, together with the slopes, allow the determination of the correlation times of the molecular motions as a function of temperature. From the free-induction-decay shapes were derived the intermolecular and intramolecular contributions to the second moment of the proton-resonance line shape. The temperature dependence of the second moment gives information about the molecular motions and the structure of solid hydrogen sulfide. Models of the structure and motion are proposed and examined.
Chemical Shifts of 14N in the NMR Spectra of Linear Triatomic Molecules and Ions
Authors: Kent J. E. , Wagner E. L.
Published: January 2005

The nuclear magnetic resonances of 14N in a series of simple linear nitrogen-containing molecules and ions have been determined by a consistent procedure, ClCN, BrCN, and NCSe− values being reported for the first time. The observed chemical shifts vary linearly over a considerable range of values with the pi-electron densities previously calculated by a LCGO—MO method. The simple shielding theory of Karplus and Pople, which considers only the paramagnetic contribution, is capable of accounting for the observed chemical shifts of these compounds in a quite satisfactory manner.
Photoionization Study of Diatomic-Ion Formation in Argon, Krypton, and Xenon
Authors: Huffman Robert E. , Katayama Daniel H.
Published: January 2005

Ionization current at wavelengths of discrete absorption lines of five resonance series of argon, krypton, and xenon has been observed in the vacuum ultraviolet. This ionization is due to a collision process between electronically excited and ground-state atoms resulting in formation of a diatomic ion and an electron. Using the helium and argon continuum light sources, it was possible to identify over 20 reacting states for each gas, and to observe that the ionization is found at every absorption line of shorter wavelength than a definite ionization threshold. Ionization thresholds observed were: Ar, 14.710±0.009; Kr, 13.004±0.007; and Xe, 11.162±0.005 eV. The energies of the ionization thresholds are in good agreement with some electron-impact appearance potentials, but the number of excited electronic states found in this investigation is much larger. From the thresholds, the following lower limits for D(X2+) are obtained: Ar, 1.049; Kr, 0.995; and Xe, 0.967 eV. Ionization yields at argon absorption lines result in values of k4/k2 (ratio of de-exciting collisions to diatomic-ion-formation collisions) from 2.5 to 0.13 and values of τk2 (product of effective radiative lifetime and diatomic-ion-formation rate constant) of 3.6×10−18 to 1.28×10−16 cm3 atom−1.
Formation of N2(A3Σu+) and N(2D, 2P) by Photodissociation of HN3 and N2O and Their Reactions with NO and N2O
Authors: Welge Karl H.
Published: January 2005

The formation of NO (A 2Σ+) and NO (B 2II) in the photolysis of N2O at 1236 and 1470 Å was investigated by observing the fluorescence of the γ and β bands. The β-band fluorescence is obtained when pure N2O is photolyzed at 1236 and 1470 Å in a flow system. The β bands are observed with vibrational excitation up to v′=3. The β bands disappear with the addition of small amounts of NO, whereas the emission of rotationally hot γ bands is obtained. The γ bands are observed with vibrational excitation up to v′=2. According to the energetics, NO (A 2Σ+) and NO (B 2II) are formed at 1470 Å as well as at 1236 Å not by direct photodissociation of N2O but by secondary reactions. No fluorescence is obtained when N2O or N2O/NO mixtures are irradiated at wavelengths ≧1600 Å, i.e., within the long-wavelength absorption band of N2O. The roles of N2 (A 3Σu+), N (2D), N (2P) are evaluated and discussed.

The emission of γ bands is also obtained in the photolysis of HN3/NO mixtures at 1470 and 1236 Å. This observation is explained by the photodissociationHN3→N2(A Σu+)+NH(X 3Σ−)followed by the reaction between N2 (A 3Σu+) and NO, yielding NO (A 2Σ+). The other possibility, that O atoms which are formed by photodissociation of NO react with HN3 to form excited NO—as in the O/N2H4 atomic flame—is excluded.
Matrix Elements between Bonded Functions
Authors: Sutcliffe Brian T.
Published: January 2005

Formulas are given for the spinless one- and two-particle density matrices and for certain other density functions in terms of bonded function wavefunctions.
Molecular Orbital Theory of Sulfur and Selenium Radicals
Authors: Chen Inan , Das T. P.
Published: January 2005

The electronic structures of various sulfur and selenium radicals were studied by semiempirical molecular orbital theory in the form of a parameter theory. The ESR data (g values) were used to determine the actual value of the parameter α, which is the coefficient of the s orbital in the bonding hybrid of the S(Se) atom in the radical. The physical significance of α so determined was studied by investigating some quantum chemical quantities such as valence state energies Ev and bond strengths B as functions of α. As a result, a criterion for the determination of the parameter value was deduced, namely, the selection of that value of α which maximizes B2 | Ev |.

From theoretical considerations and experimental data in the literature, the relative signs of the principal values of the hyperfine-structure tensor of selenium were determined, and the magnitudes of the isotropic and anisotropic components were evaluated.
Crystal Structure of CH3NH3NiCl3
Authors: Willett Roger D.
Published: January 2005

The crystal structure of the new complex, CH3NH3NiCl3, has been determined. The compound crystallizes in the space group Cmcm with a=6.94, b=14.94, and c=5.95 Å. Each nickel ion has a distorted octahedral coordination with two chloride ions at 2.405 Å and four chloride ions at 2.351 Å. Adjacent octahedra along the c axis share faces to form infinite (NiCl3)nn— chains parallel to this axis. The electronic absorption spectrum has been measured over the range 6000–45 000 cm−1. The spectrum is characteristic of octahedral d8 complexes and yields a value of Dq=700 cm−1 for the nickel chloride complex.
Photolysis of cis-Hexene−2 and cis-Butene−2 at 2026 and 2062 Å
Authors: Chesick John P.
Published: January 2005

cis-Hexene−2 and cis-butene−2 were photolyzed directly using 2026- and 2062-Å radiation at varying methane pressures up to 52 cm and olefin pressures of 2 cm. Collisional stabilization of the trans isomer in each case competes with the first-order decomposition reactions: C6H12*→ lim (1)C4H7+C2H5,C4H8*→ lim (2)C3H5+CH3,→ lim (3)C4H7+H.From the observed pressure dependencies, the values of the first-order rate constants are k1=8.2×107 sec−1, k2=5.0×108 sec−1, k3=3.5×108 sec−1. Quantum yields for the total of trans olefin and cleavage Reaction (2) are of the order of unity for both butene−2 and hexene−2 photolyses. It is concluded that the cleavage reactions occur after rapid internal conversion to the ground electronic states. The cis—trans isomerization and an isomerization to the 1-olefin (5% of total reaction) occur in a time short compared to the time between deactivating collisions at the highest pressures.
Intrinsic Photoconduction in Anthracene Crystals
Authors: Chaiken Robert F. , Kearns David R.
Published: January 2005

The dc photoconductance of ``pure'' anthracene crystals, anthracene crystals doped with tetracene and acridine, and ``pure'' anthracene melts in the uv region (2500–4000 Å) has been investigated. A novel conduction cell allowed crystals to be grown in situ between electrically conducting, semitransparent electrodes, and photocurrent measurements to be carried out at temperatures up to and above the anthracene melting point (>220°C). A photocurrent peak at ∼2800 Å, which was first reported by Castro and Hornig in pulsed-light experiments, has been confirmed. The photocurrent spectral-response data and the change in the spectral response, produced by adding the fluorescence quenchers tetracene or acridine to the anthracene, or by melting the crystals, demonstrate that 2800-Å light generates carriers by a direct optical transition to a conducting state of the crystal. The threshold for this direct ionization process (i.e., a band-to-band transition) occurs at ∼3100 Å or ∼4.0 eV. The quantum yield for carrier generation at 2800 Å is on the order of 10−4 or greater. Excitation in the 4000–3100-Å region generates carriers by a mechanism which involves singlet exciton states as intermediates, and the interaction of these excitons with surface or near-surface impurity sites. Some preliminary data on intrinsic photoconduction in pyrene crystals are also reported.
Sources of Intensity in the 1U(n, π)←1A Band of Benzophenone
Authors: Chandler W. D. , Goodman Lionel
Published: January 2005

A vibronic perturbation experiment is presented in which the polarized excitation spectra (77°K) and and absorption spectra of benzophenone and 4,4′-dimethylbenzophenone were compared in the region 2500 to 4000 Å. This experiment supports the view that the n→π band in benzophenone is essentially forbidden, even though the probable conformation is C1, and that the intensity comes principally from vibronically induced borrowing from 1(Lb+Lb)←1A and 1K←1A (charge transfer) π→π promotions. A secondary but significant source for vibronic borrowing is the 1(Lb—Lb)←1A π→π transition.
Energetic and Angular Studies of ArD+ and N2D+ Formation
Authors: Doverspike L. D. , Champion R. L. , Bailey T. L.
Published: January 2005

The reactions Ar++D2→ArD++D and N2++D2→N2D++D have been studied with an angular ion-scattering apparatus at ion laboratory energies in the range 2–100 eV. Kinetic-energy distributions as well as angular distributions of the product ions have been determined. The experimental method consists of directing a mass-analyzed and velocity-selected ion beam into a collision chamber containing target gas at low pressure. The product ions are velocity analyzed with a 127° electrostatic velocity selector and mass analyzed in a quadrupole field radio-frequency mass filter. The product-ion analysis and detection system rotates about the center of the scattering region. It is found that the observed Q values for these reactions (where Q is the energy transformed from internal to translational) show a marked dependence on the primary-ion kinetic energy, E1. The Q values for both reactions are endothermic over the entire energy range of these experiments, being approximately zero at the lowest energies and exhibiting endothermic maxima in the region 50<E1<60 eV. It is shown that these maxima correspond to the formation of internally excited product ArD+ and N2D+ ions, with excitation energies approximately equal to the dissociation energies for ArD+→Ar+D+ and N2D+→N2+D+. The product-ion kinetic-energy distributions also give evidence of back scattering in the center-of-mass system. The energetic and angular features of both reactions are essentially the same, indicating that the collision mechanisms leading to the formation of both product ions do not differ significantly.

The experimental results indicate that both reactions proceed according to a ``pickup'' mechanism at moderate coilision energies. At very low collision energies the results suggest that complex formation may become important.
Lower-Bound Procedure for Energy Eigenvalues by the Partitioning Technique
Authors: Choi Jong H. , Smith Darwin W.
Published: January 2005

A lower-bound procedure for obtaining energy eigenvalues by use of the partitioning technique and bracketing theorem, which have been developed by Löwdin, is extended to the case of a multidimensional reference manifold and is applied to the ground state of the two-electron isoelectronic series. Except for H−, the agreement between upper and lower bounds is quite satisfactory. The process of obtaining lower bounds for excited states is considered.