bluuebunny/crossref_metadata_2025 huggingface dataset:
Six-dimensional calculation of the vibrational spectrum of the HFCO molecule
Authors: Viel Alexandra , Leforestier Claude
Published: July 2002

Bound energy levels, up to 5000 cm−1 of internal excitation, have been computed for the HFCO molecule. An exact six-dimensional (6D) quantum Hamiltonian, expressed in terms of Jacobi vectors, has been used. It is shown to lead to a compact form of the kinetic energy operator, easy to implement in the calculations. The primary discrete variable representation (DVR) basis set has been contracted by means of the adiabatic pseudospectral method of Friesner et al. [J. Chem. Phys. 99, 324 (1993)]. Two different, global, potential energy surfaces have been considered. The calculated energy levels have been successfully assigned by an automatic labeling procedure. These levels have been compared to the experimental results, providing a test of the accuracy of the existing surfaces.
Lateral interactions of CO in the (2×1)p2mg structure on Pd(110): Force constants between tilted CO molecules
Authors: Kato Hiroyuki , Okuyama Hiroshi , Ichihara Shigeru , Kawai Maki , Yoshinobu Jun
Published: July 2002

Intermolecular interactions between tilted CO molecules in the (2×1)p2mg structure on Pd(110) were studied by means of high-resolution electron energy-loss spectroscopy (HREELS). We measured the distinctive dispersion of the C–O internal stretching mode and the hindered translational modes. The dispersion of the C–O internal stretching mode is well explained by the dynamic dipole–dipole interaction. On the other hand, the dispersion of hindered translational modes is anisotropic. In contrast to the constant T[001] mode along [001], both the T[001] and T[11̄0] modes observed along [11̄0] are dispersive. The dispersive feature of the hindered translational mode along [11̄0] was not observed for twofold periodic CO in a p(2×1) structure close to half coverage on Pd(110). Therefore, the anisotropic dispersion clearly reflects a short-range interaction between the CO molecules adsorbed at the nearest neighbor sites. From the analysis of the distinctive dispersion, a strong repulsive force-constant is obtained, i.e., 10.5±1.5 N/m, which quantitatively asserts that the tilted CO is formed by the steric repulsion between the nearest neighbor molecules.
Distributed polarizabilities derived from induction energies: A finite perturbation approach
Authors: Celebi Nihan , Ángyán János G. , Dehez François , Millot Claude , Chipot Christophe
Published: July 2002

An approach based on finite perturbation theory is proposed for deriving models of distributed polarizabilities from quantum mechanically determined induction energies. It relies on the construction of a grid of points, over which the induction energy resulting from the interaction of a charge with the molecule of interest is evaluated at the desired level of approximation. Distributed polarizabilities of any order are then fitted by solving the normal equations of the least-squares problem, the solution of which provides an optimal description of induction effects. The method is probed by examining several models of distributed polarizabilities of increasing complexity in the case of water, methanol, acetonitrile, and benzene. At a reasonable order of multipole expansion, atomic polarizabilities derived using this approach are found to reproduce the corresponding molecular polarizabilities with an appropriate accuracy. The careful choice of the parameters to be fitted appears to be a key factor for obtaining physically realistic models.
Calculation of the cadmium–water interface
Authors: Price David L.
Published: July 2002

This paper presents the results of a very nearly ab initio calculation of the molecular and electronic distributions at the interface of hcp cadmium and liquid water. The calculated results were obtained by combining a molecular dynamics simulation for the H2O molecular distributions with a self-consistent density functional calculation for the valence electron density of the cadmium surface. The method employs a three-dimensionally periodic unit cell, uses standard molecular dynamics potentials for H2O–H2O interactions, and calculates a self-consistent electronic structure for the metal at each time step of the molecular dynamics simulation, with the electron–H2O and electron–Cd interactions represented by pseudopotentials. The electronic and H2O distributions of the Cd–water interface are obtained both for zero applied potential, and for a range of electric potentials applied across the interface. Results are given for the equilibrium structure of interface, and its response to applied potentials. An analysis of the electrostatics of the interface yields a prediction for the compact capacitance of the cadmium–electrolyte interface, which is compared to experiment.
Topologically induced glass transition in dense polymer systems
Authors: Rosche Matthias , Winkler Roland G. , Reineker Peter , Schulz Michael
Published: July 2002

The glass transition in hard core polymer systems is analyzed by a Monte Carlo simulation. The method used is based on a novel continuous fluctuating bond method, which allows for the comparison with well-known liquids of spherical hard core particles. It is demonstrated that the glass transition of hard core polymers is a prevented first-order phase transition due to the bonds of the polymer chains (topological restrictions). The characteristic slow down of the molecular dynamics is a result of the formation of locally ordered structures. Furthermore, the characteristically temperature-dependent α and β processes and an additional strongly localized and very fast process are detected.
Quantum scattering calculations of energy transfer and isomerization of HCN/HNC in collisions with Ar
Authors: Christoffel Kurt M. , Bowman Joel M.
Published: July 2002

Quantum scattering calculations are reported for zero impact parameter collisions of Ar with HCN/HNC for three fixed angles of attack of Ar with respect to the CN axis, in the total energy range 16 000–20 000 cm−1, and using a new Ar–HCN interaction potential based on ab initio data. We find that this interaction potential only weakly couples localized HCN and localized HNC states. As a result, although isomerization is energetically possible in much of the energy range considered, the probability of collision-induced isomerization is found to be small. Detailed analysis of our scattering results shows that “head on” collisions in which the Ar atom impinges on the H end of the molecule are more effective in promoting T→V energy transfer than are “nearly perpendicular” and “tail on” (opposite to the H atom) collisions. Significant energy transfer processes between translation and vibration involve the bending mode ν2 either through pure bend excitation/deexcitation or through smaller ΔE processes in which a larger number of ν2 quanta are exchanged for a smaller number of ν1 or ν3 quanta. Examination of our distributions of inelastic transition probabilities for highly excited states, including a delocalized state, suggests that they mimic a biexponential gap distribution.
Resolving the controversy over the second ionization potential of the nitrate free radical NO3
Authors: Heryadi Dodi , Yeager Danny L.
Published: July 2002

Two experimental studies determining the ionization potentials (IPs) of a nitrate free radical have recently been done. The first study performed using discharge flow-photoionization mass spectroscopy (PIMS) determined the adiabatic ionization potential at 12.57 eV. The second study using the HeI photoelectron spectroscopy (PES) observed five bands with the five lowest vertical ionization potentials of NO3 at 12.55, 13.18, 13.62, 14.05, and 15.54 eV. The second IP determined using PES (at 13.18 eV) has been questioned due to its absence in the spectrum obtained using the PIMS experiment. We use our theoretical method, the multiconfigurational spin tensor electron propagator method (MCSTEP), to help resolve the controversy over the ionization potential of NO3. We perform MCSTEP calculations on NO3 using the standard cc-pVDZ and cc-pVTZ basis sets at D3h and C2v geometries. Our results at both of these two symmetries support the experimental results obtained using PES.
Effects of bath relaxation on dissipative two-state dynamics
Authors: Cao Jianshu
Published: July 2002

A formal solution to the two-state Liouville equations is used to derive quantum equations of motion for dissipative two-state systems without making the assumption of a harmonic bath. The first-order equation of motion thus obtained is equivalent to the noninteracting blip approximation and can be systematically improved by introducing high-order cumulants. The second-order equation of motion incorporates effects of bath relaxation on two-state dynamics and leads to an effective nonadiabatic rate expression, which in the classical limit reduces to the well-known electron transfer rate formula. Numerical results with an Ohmic bath show saturation at large coupling constants due to the rate-limiting effect of relatively slow bath relaxation, and a comparison with classical calculations demonstrates larger rate constants at low temperature when quantum coherence is taken into account.
A density functional theory study of site-specific methyl reaction on MoO3(010): The effects of methyl coverage
Authors: Chen M. , Friend C. M. , Kaxiras Efthimios
Published: July 2002

We report density functional theory calculations, using pseudopotentials with a plane wave basis, of methyl adsorbed on the MoO3(010) surface at 0.5 and 1.0 ML coverages. The MoO3 surface is modeled by a one-layer slab. Methyl is adsorbed most strongly over the terminal oxygen, where methoxy is formed. Over the bridging oxygens, qualitatively different results are obtained depending on the coverage of methyl. At 0.5 ML, methoxy is formed over the bridging oxygens, with an associated relaxation of the surface caused by a repulsion between the methyl and the terminal oxygen. For the 1.0 ML coverage, methyl is not stable and decomposes. Over the asymmetric bridging oxygen, methyl reacts to form formaldehyde and hydroxyl, while over the symmetric bridging oxygen a formyl species and water are produced. The hydroxyl and water are formed via hydrogen transfer to a terminal oxygen. The bonding and reaction of methyl over the various oxygen species are analyzed and discussed using charge density difference plots as well as the crystal orbital overlap projection (COOP). For the 0.5 ML methyl coverage, this analysis shows that the tilting of the terminal oxygen bond weakens this bond slightly. For the 1.0 ML methyl coverage, the COOP plots indicate that the decomposition of methyl over the bridging oxygens is not as stable as methyl over the terminal oxygen because the presence of the carbon fragments affects the electronic structure, and causes a weakening of the Mo–terminal oxygen bond. These results are discussed in the context of partial oxidation reactions.
Thermochemical and kinetic parameters for hydrogen bonded clusters, derived from avalanche condensation flux measurements
Authors: Bauer S. H. , Zhang Yi-Xue , Wilcox C. F.
Published: July 2002

The kinetic molecular model (KMM) was applied to recently reported extensive measurements of condensation flux levels developed under homogeneous conditions from supersaturated vapors of water and n-pentanol, in inert gas carriers. These data span wide ranges in temperatures and critical supersaturations (css). The calculated fluxes reproduced those observed (defined: number of droplets generated per cm3-s) within a factor 2, utilizing a narrow range of adjustable parameters. From the derived kinetic and thermochemical parameters one may derive estimates of size-dependent entropies for clusters. Thus, the derived entropy per mole of a 13 unit cluster of water molecules, at 233 K, is 233 eu.
K-scrambling in a near-symmetric top molecule containing an excited noncoaxial internal rotor
Authors: Ortigoso Juan , Hougen Jon T.
Published: July 2002

Classical trajectories on rotational energy surfaces and coherent-state quantum projections have been used to study an asymmetric-top molecule containing a freely rotating internal symmetric top whose symmetry axis is not coincident with a principal axis of the molecule. Stationary points on the rotational energy surface, which strongly influence the trajectories, increase in number from two to four to six as J/n increases from zero to infinity (where J is the total and n is the free-internal-rotor angular momentum). For some J/n values trajectories can arise that sample a large fraction of K values (where K is the z-axis projection of J), corresponding in quantum wave functions to extensive K mixing in the symmetric-top basis set |J,K〉. When such mixing cannot be made small for any choice of z axis, we call it K scrambling. For typical values of the torsion–rotation coupling parameter ρ, rotational eigenfunctions for a given J and torsional state turn out to be quite different from eigenfunctions for the same J in some other torsional state. Nonzero rotational overlap integrals are then distributed among many rotational functions for each (n,n′) pair, which may, in turn, contribute to internal rotation enhancement of intramolecular vibrational energy redistribution. We have also examined near-free-rotor levels of our test molecule acetaldehyde, which arise for excitation of ten or more quanta of methyl group torsion, and find that barrier effects do not change the qualitative picture obtained from the free-rotor treatment.
Phase equilibria and thermodynamic properties of hard core Yukawa fluids of variable range from simulations and an analytical theory
Authors: Shukla Keshawa P.
Published: July 2002

New Gibbs ensemble Monte Carlo (GEMC) simulation results for vapor/liquid phase equilibria and new Monte Carlo simulation results for structure and thermodynamic properties of the hard core Yukawa fluids of variable range (HCYF-VR) are presented. Using the inverse temperature expansion of the free energy of mean spherical approximation a new version of the analytical theory of HCYF-VR has been developed. GEMC results for 108, 216, and 500 particles show a significant system size dependence of the vapor/liquid phase diagram. Comparisons of theoretical predictions with simulation data show that the analytical theory is highly reliable in describing structure, thermodynamic properties and phase equilibrium of HCYF-VR over a range of the attraction parameter and thermodynamic conditions. Both simulation and theoretical results show that the range of vapor/liquid equilibrium temperature shrinks as the range of interaction decreases. Theoretical results for the critical point and triple point temperatures illustrate that the vapor/liquid phase diagram tends to flatten out for sufficiently short range of the attraction, finally resulting in fluid/solid phase equilibrium, in agreement with simulation results. In addition, the analytical theory has been extended to predict thermodynamic properties of several binary HCYF-VR mixtures accurately.
Vibrational mode and collision energy effects on proton transfer in phenol cation–methylamine collisions
Authors: Kim Ho-Tae , Green Richard J. , Anderson Scott L.
Published: July 2002

Mass-analyzed threshold ionization has been used to prepare vibrationally state-selected phenol cations, that were then reacted with methylamine at collision energies ranging from 0.1 to 2 eV. Integral cross sections and product recoil velocity distributions are reported. Ab initio calculations of stationary points on the surface and RRKM (Rice–Ramsperger–Kassel–Marcus) analysis of complex lifetimes are also presented for comparison. The only reaction observed over the entire energy range is exoergic proton transfer (PT). For ground-state reactants, the PT cross section is reduced by increasing collision energy, such that the reaction efficiency declines from ∼71% at low Ecollision to ∼50% at 2 eV. Excitation of either v6a or v12 vibrations inhibits reaction over the entire collision energy range, with the effect being somewhat mode-specific and increasing with increasing Ecollision. At low Ecollision, both vibrational and collision energy inhibit reaction with similar efficiency. Collision energy effects diminish at high Ecollision, while vibration continues to have a strong effect. Product ion velocity distributions are approximately forward–backward symmetric at Ecollision⩽1 eV, but are backward peaked at high energies. Mechanistic implications of these results are discussed.
Structure and energetics of ArnNO− clusters from ab initio calculations
Authors: Jakowski Jacek , Kłos Jacek , Chałasiński Grzegorz , Severson Mark W. , Szczȩśniak M. M. , Cybulski Sławomir M.
Published: July 2002

The potential energy surface for the ground state of the Ar–NO−(3Σ−) complex has been calculated at the unrestricted Mo/ller–Plesset perturbation theory through the fourth order (UMP4). Calculations have been performed using the augmented correlation-consistent polarized triple zeta basis set supplemented with bond functions (aug-cc-pVTZ+bf ). The global minimum with a well depth of approximately 651 cm−1 has been found for an approximate T-shaped structure (R=6.28 ao and Θ=83.62°). Two other, local minima correspond to two collinear forms, Ar–N–O and N–O–Ar. All these minima are located in the regions of local reduction of exchange repulsion. The ground vibrational state dissociation energy D0 determined by the collocation method has been found to be 587 cm−1. Several rovibrational states have been predicted and characterized. The ground-state complex assumes a fairly rigid T-shaped structure. The trimer, Ar2NO−(3Σ−), is also of the T-shaped-cross structure, and the pairwise equilibrium and dissociation energies amount to 1402 and 1260 cm−1, respectively. The three-body nonadditive effects raise the equilibrium energy by 41 cm−1. The minimum-energy structures of clusters Arn=2,3…,12-NO−(3Σ−) have also been found, from the pairwise additive potential, and ground-vibrational states have been simulated by means of rigid-body diffusion Monte Carlo.
The vibrational spectrum of solid ferrocene by inelastic neutron scattering
Authors: Kemner E. , de Schepper I. M. , Kearley G. J. , Jayasooriya U. A.
Published: July 2002

We calculate the spectrum of internal vibrations of a single ferrocene Fe(C5H5)2 molecule using ab initio density functional theory (without free parameters) and compare this with inelastic neutron scattering data on ferrocene in the solid state at 28 K. Due to the good agreement, we can assign each vibrational mode to each observed peak in the neutron spectrum and so remove ambiguities existing in the literature. There is also consistency between the calculated potential energy of a single ferrocene molecule for different orientations, φ, of the two cyclopentadienyl C5H5 rings with respect to each other, which shows a potential barrier of 0.9 kcal/mol, and electron diffraction, and between the calculated shallow minimum at φ=9 deg and x-ray diffraction.
Enumeration of cubic lattice walks by contact class
Authors: Crippen Gordon M.
Published: July 2002

Self-avoiding walks on a three-dimensional (3D) simple cubic lattice are often used to model polymers, especially proteins. The Hamiltonian is generally taken to be a function of contacts between sequentially nonadjacent residues. The set of all conformations having a particular set of contacts occupies the same energy level, and one would like to estimate the degeneracy or chain entropy of the level. Degeneracies observed in an exhaustive enumeration of short chain configurations are fitted to simple empirical formulas depending on the length of the chain, the number of contacts, and statistics related to the particular set of contacts.
Self-organization of comblike copolymers with end-functionalized side chains: A cellular-automaton-based simulation
Authors: Shirvanyanz David G. , Pavlov Alexander S. , Khalatur Pavel G. , Khokhlov Alexei R.
Published: July 2002

Using the cellular-automaton-based simulation technique, we study the processes of self-organization in the systems of comblike copolymers with strongly attracting groups located at the ends of side chains. It is found that at a certain critical association energy, dependent both on polymer volume fraction and on the chemical composition of the copolymers, a micellar phase is nucleated. For the combs with large linear grafting density, a weak extension of the macromolecules is observed as attraction between end groups is increased. We find that the micelle formation observed in the sufficiently dense systems is mainly a result of intermolecular association. From the analysis of the static structure factors and snapshot pictures, it is concluded that the system is spatially inhomogeneous on the intermediate length scales related to the average intermicellar distances. Strong attraction stabilizes the aggregates (multiplets) that serve as junction points of a temporary network (micellar gel). We observe the formation of a specific space-filling weblike network in which strongly attracting side-chain ends group into multiplets which are wrapped by neutral polymer sections connecting these multiplets.
Vibrationally excited states of CH3CFCl2: Intramolecular vibrational redistribution and photodissociation dynamics
Authors: Melchior A. , Chen X. , Bar I. , Rosenwaks S.
Published: July 2002

Utilizing vibrationally mediated photodissociation of jet-cooled CH3CFCl2 enabled monitoring of the second (3νCH) and third (4νCH) overtones of the methyl in the ground electronic state. The excited molecules are photodissociated by ∼235 or 243.135 nm photons that further tag Cl(2P3/2)[Cl] and Cl(2P1/2)[Cl*] isotopes or H photofragments via mass selective (2+1) resonantly enhanced multiphoton ionization. The vibrational spectra are characterized by a multiple peak structure related to C–H stretches and to Fermi resonating levels involving the CH3 deformation. The cooling in the expansion reduces the rotational and vibrational congestion and affords a determination of the splittings and the upper limits for homogeneous broadening of the transitions. The highest-frequency peak of 4νCH exhibits an additional splitting, related to coupling of the mixed stretch–deformation states with other modes of the molecule. The yield of all three photofragments increases as a result of preexcitation, demonstrating that the energy is not preserved in the excited bond but rather flows to the C–Cl bond. The initial vibrational state preparation not only enhances C–Cl and C–H bond cleavage but also affects the Cl*/Cl branching ratio, as compared to the nearly isoenergetic one-photon 193 nm photolysis of vibrationless ground state CH3CFCl2, implying that it alters the photodissociation dynamics.
A theoretical study on the ionization of CO2 and CS2 with analysis of the vibrational structure of the photoelectron spectra
Authors: Takeshita Kouichi , Shida Norihiro , Miyoshi Eisaku
Published: July 2002

Ab initio calculations have been performed to study the molecular structures and the vibrational levels of the low-lying ionic states (Πg2, Πu2, Σu+2, and Σg+2) of CO2 and CS2. The global regions of the potential energy surfaces have been obtained by multireference single and double excitation configuration interaction calculations. The vibrational calculations using the explicit vibrational Hamiltonians have been used for the vibrational analysis. The equilibrium molecular structures and the vibrational analysis of the ionic states are presented. The theoretical ionization intensity curves including the vibrational structures of the ionic states are also presented and are compared with the photoelectron spectra.
Constraint dynamics for quantum Monte Carlo calculations
Authors: Sarsa A. , Schmidt K. E. , Moskowitz J. W.
Published: July 2002

We describe how to apply classical constraint dynamics to problems in diffusion Monte Carlo. We apply the method to rigid and nonrigid water molecules with an internal rotational degree of freedom. The method is applicable to a wide variety of problems.
A joint theoretical–experimental investigation of the lower bound states of the NO(X 2Π)–Ar complex
Authors: Kim Yangsoo , Fleniken J. , Meyer Henning , Alexander Millard H. , Dagdigian Paul J.
Published: July 2002

In an extension of recent work [Y. Kim, K. Patton, J. Fleniken, and H. Meyer, Chem. Phys. Lett. 318, 522 (2000)], overtone pumping followed by resonantly enhanced multiphoton ionization (REMPI) detection is used to record spectra corresponding to excitation of the lowest five bend–stretch vibrational levels of the NO(X 2Π,v=2)–Ar complex. High-quality ab initio potential energy surfaces, coupled-electron-pair (CEPA) and coupled cluster single double triple [CCSD(T)], are used to predict the positions of these same five states, but in the NO(X 2Π,v=0)–Ar complex. The vibrational wave functions and basis set expansion coefficients, determined within the adiabatic bender model, are then used to simulate the observed spectrum for excitation of the NO(X 2Π, v=2)–Ar complex. The overall position and rotational substructure matches the experiment extremely well, particularly when the simulation is based on the presumably more accurate CCSD(T) potential energy surfaces.
Four-dimensional quantum mechanical treatment of penta-atomic systems: Case H2+C2H→H+C2H2; total reactive probabilities, cross sections, and rate constants
Authors: Szichman H. , Gilibert M. , González M. , Giménez X. , Navarro A. Aguilar
Published: July 2002

An advanced quantum mechanical model for the treatment of the dynamics of a diatom–triatom molecule system is presented here. The model has been applied to the study of the reactive process H2+C2H→H+C2H2, using a four-dimensional (4-D) infinite-order sudden approximation scheme when seven of nine degrees of freedom are explicitly considered (the two others are being reduced by means of an averaging of the potential energy surface around the out-of-plane angles). Using a previously reported surface for this reaction [J. Chem. Phys. 101, 8646 (1994)] computations have been carried out to obtain total reactive probabilities, cross sections, and rate constants. A value of 2.68×10−13 cm3 molecule−1 s−1 was determined for the thermal rate constant at room temperature, in good agreement with the above referenced theoretical calculation as well as with available experimental data.
Rayleigh–Ritz calculation of the activation rate in the spatial diffusion regime
Authors: Drozdov Alexander N. , Tucker Susan C.
Published: July 2002

We propose a Rayleigh-quotient-based perturbation method for estimating the least nonvanishing eigenvalue of the Fokker–Planck equation in the spatial diffusion regime. Comparison of the resulting expression against exact numerical rates in a symmetric double well produces excellent agreement at all barrier heights. The corresponding relative error is lower by more than an order of magnitude than those of existing finite-barrier expansions.
Nonadditive intermolecular potential and thermodynamic properties of ethane
Authors: Pádua Agı́lio A. H. , Trusler J. P. Martin
Published: July 2002

New intermolecular potential models incorporating nonadditive interactions are proposed for the ethane molecule. Three functional forms for the pair potentials were tested. Each was based on an initial fit to ab initio calculations of the pair interaction energy, followed by a first refinement fit to second virial coefficients. A nonadditive three-body contribution was then included, leading to a density-dependent effective pair potential. Finally, the resulting models were optimized against experimental thermodynamic data in the compressed gas region. In the interest of computational efficiency, thermodynamic properties were calculated from the intermolecular potentials using the molecular integral-equation theory with a recent approximation for the bridge function. The accuracy of the closure was verified by Monte Carlo simulations. The intermolecular potentials are able to reproduce the p(ρ,T) surface of ethane with an overall standard deviation of 0.2% up to the saturation line, or at densities up to the critical density, over a wide range of temperatures.
Experimental determination of excitonic levels in α-oligothiophenes
Authors: Kouki Fayçal , Spearman Peter , Valat Pierre , Horowitz Gilles , Garnier Francis
Published: July 2002

The effects of intermolecular interactions on the optical spectra of oligothiophenes are examined. Absorption spectra of isolated molecules are calculated and experimentally recorded in a rigid host matrix whereby molecules are distributed randomly or organized unidirectionally. Absorption spectra of thin films in an ordered and disordered state are given. Ordered films have three principal spectral regions which are discussed in terms of classical exciton theory. Absorption spectra in transmission of single crystals of quinquethiophene and sexithiophene are analyzed. The lowest optically allowed transition in the crystal corresponds to the lowest Davydov component. It consists of a sharp peak that is observed for even-numbered oligothiophenes in b polarization, and absent for odd-numbered rings due to the perfect alignment of the transition dipole moment with the long molecular axis. The upper Davydov component is viewed in both thin film and single crystal spectra. In between the two principal Davydov components lies a broadband that is tentatively attributed to charge-transfer states or to a noninteracting molecular transition reminiscent of isolated matrix spectra. The Davydov splitting of the first optically allowed transition is determined to be about 10 000 cm−1 and increases slightly with chain length. The Herzberg–Teller region in 6T reveals a dominant coupling mode of 340 cm−1. Vibronic structure in excitation and emission spectra shows peaks of 1460 cm−1 spacing.
On the use of the second order split-operator method
Authors: Eno Larry
Published: July 2002

We examine the second order split-operator propagator of Fleck et al. as it functions to solve the time-dependent Schrödinger wave equation. In particular we examine the usefulness of dividing the propagator into its two lower order component propagators each of which propagates the wavepacket on one half of the time-step of the full propagator.
The ground-state phase behavior of model Langmuir monolayers
Authors: Opps S. B. , Nickel B. G. , Gray C. G. , Sullivan D. E.
Published: July 2002

A coarse-grained model for surfactant molecules adsorbed at a water surface is studied at zero temperature to elucidate ground-state tilt ordering. The surfactants are modeled as rigid rods composed of head and tail segments, where the tails consist of effective monomers representing methylene CH2 groups. These rigid rods interact via site–site Lennard-Jones potentials with different interaction parameters for the tail–tail, head–tail, and head–head interactions. In this work, we study the effects due to variations in both the head diameter and bond length on transitions from untilted to tilted structures and from nearest-neighbor (NN) to next-nearest-neighbor (NNN) tilting. Coupling between tilt ordering and lattice distortion is also considered. We provide a molecular derivation of a scaling relation between tilt angles and distortion obtained previously by phenomenological arguments. Due to the discrete site–site nature of the model interactions, the predicted ground-state phase behavior is much richer than evidenced by models employing cylindrical rods. In particular, we have found transitions between different phases (i.e., NN–NN′ and NNN–NNN′) of similar symmetry, which may have experimental support. We have also examined the sensitivity of the transitions to details of the model, such as replacing Lennard-Jones head–head and head–tail potentials by purely repulsive interactions.
High-resolution laser spectroscopy of YbS: Deperturbation analysis of the A0+–X0+ transition
Authors: Melville Todd C. , Coxon John A. , Linton Colan
Published: July 2002

The A0+–X0+ electronic transition of Yb172S32, Yb174S32, and Yb176S32 has been rotationally analyzed for the first time. Doppler-limited laser excitation spectroscopy with selective detection of fluorescence was used to obtain spectra of the 0–0, 0–1, 1–1, 1–2, 2–2, and 2–3 bands with a measurement precision of approximately 0.003 cm−1. The 2–2 and 2–3 bands were found to be perturbed by a level crossing that occurs in the A0+ υ=2 level. In total, over 1500 line positions have been measured, assigned, and employed in least-squares fits of molecular parameters. The principal deperturbed results for the X0+ state, which arises primarily from the Yb2+(4f14)S2− electronic configuration, are Re=2.3591(2) Å and ωe(174YbS)=366.714(2) cm−1, and for the A0+ state, R0(174YbS)=2.3905(2) Å.
Connections on infinitesimal fiber bundles and unified theories
Authors: Sen D. K.
Published: July 2002

We provide an intrinsic coordinate-free formalism of Jordan’s version of five-dimensional Kaluza–Klein or projective theory of relativity in terms of the so-called infinitesimal fiber bundles, whose structures are slightly more general than principal fiber bundles with connections. Higher-dimensional generalizations are then suggested, thereby providing a more comprehensive unified theory.
Elasticoviscous flow due to a plate which starts oscillating in the presence of a parallel stationary plate
Authors: Choubey Krishna Raj
Published: July 2002

In this paper, the flow of a particular class of a non-Newtonian fluid between two parallel plates has been considered, employing a well-known transform technique, when one plate is stationary and the other plate suddenly starts oscillating. Both finite Fourier sine transform and Laplace transform techniques have been employed to solve the basic differential equations. The flow phenomenon has been characterized by the parameters S and ω. Expressions for the velocity have been calculated. Effects of the viscoelastic parameter and the frequency parameter on the fluid flow have been studied through several tables.
Nontrivial zeros of the Wigner (3-j) and Racah (6-j) coefficients. I. Linear solutions
Authors: Brudno Simcha
Published: July 2002

Some formuals for nontrivial zeros in the 3-j and 6-j symbols have been found.
Titchmarsh–Weyl theory and its relations to scattering theory: Spectral densities and cross sections; Theory and applications
Authors: Brändas Erkki , Rittby Magnus , Elander Nils
Published: July 2002

The radial equation (or set of equations) derived in scattering theory is analyzed by means of Titchmarsh–Weyl theory for singular second-order differential equations. In particular we have focused on the spectral density concept and the corresponding relation to the scattering cross section. The method of complex deformations is brought in as a necessary ingredient in the evaluation of the underlying pole strings, which together with the background build up the actual dispersion relation data. The analysis is supported by numerical applications to a centrifugal family of simple potentials.
Hamilton–Jacobi formulation and quantum theory of thermal wave propagation in the solid state
Authors: Mandelis Andreas
Published: July 2002

A mathematical formalism has been developed for the description of the propagation of thermal waves in solids. The theory is based on the analogy between thermal waves and mechanics as manifested upon expressing the heat conduction equation in the Hamilton–Jacobi formalism. The transition of the classical formulation to quantum mechanics is accomplished by defining thermal wave operators for the generalized coordinates and the canonically conjugated momenta. The resulting theory shows that propagating, albeit heavily damped, thermal waves can be formally described by a quantum mechanical thermal harmonic oscillator (THO). The expectation values of observables, derived from Ehrenfest’s theorems, are found to be of practical importance for the description of the thermal wave field in solids with inhomogeneous thermal and thermodynamic properties.
Compact quantum systems: Internal geometry of relativistic systems
Authors: Barut A. O. , Bracken A. J.
Published: July 2002

A generalization is presented of the kinematical algebra so(5), shown previously to be relevant for the description of the internal dynamics (Zitterbewegung) of Dirac’s electron. The algebra so(n+2) is proposed for the case of a compact quantum system with n degrees of freedom. Associated wave equations follow from boosting these compact quantum systems. There exists a contraction to the kinematical algebra of a system with n degrees of freedom of the usual type, by which the commutation relations between n coordinate operators Qi and corresponding momentum operators Pi, occurring within the so(n+2) algebra, go over into the usual canonical commutation relations. The so(n+2) algebra is contrasted with the sl(l,n) superalgebra introduced recently by Palev in a similar context: because so(n+2) has spinor representations, its use allows the possibility of interpreting the half-integral spin in terms of the angular momentum of internal finite quantum systems. Connection is made with the ideas of Weyl on the possible use in quantum mechanics of ray representation of finite Abelian groups, and so also with other recent works on finite quantum systems. Possible directions of future research are indicated.
The relation between the (N )- and (N−1)-electron atomic ground states
Authors: Briet P. H.
Published: July 2002

The relations between the ground states of an N- and (N−1)-electron atomic system are studied. It is shown that in some directions of the configuration space, the ratio of the N-electron atomic ground state to the one-particle density is asymptotically equivalent to the (N−1)-electron atomic ground state.
On the asymptotics of distributions with support in cone
Authors: Berceanu S. , Gheorghe A.
Published: July 2002

The asymptotic behaviors of tempered distributions with support in a convex, closed cone are classified by means of group theory. The notion of regularly varying distribution is introduced. An Abelian–Tauberian theorem for regularly varying tempered distributions, which generalizes the one-dimensional Abelian–Tauberian theorem of Hardy–Littlewood–Karamata and the many-dimensional extension due to Vladimirov, is proved. Applications to n-point functions are also presented.
The vector form of the neutrino equation and the photon neutrino duality
Authors: Mickelsson Jouko
Published: July 2002

A new form of the vector wave equation for a neutrino is derived that makes the relation to the massive case more transparent than that given by Reifler. Some new aspects of the photon neutrino duality are discussed.
The adsorption of simple particles on a 2×N lattice space
Authors: Hock J. L. , McQuistan R. B.
Published: July 2002

Utilizing a 15-term recursion relation that describes exactly the composite nearest neighbor degeneracy for simple indistinguishable particles on a 2×N lattice, the adsorption isotherm is calculated and it is shown analytically that coverage as a function of the gas phase pressure exhibits no discontinuity, i.e., that no phase transition can occur.
Evaluation of the self-energy of a droplet interacting via a Yukawa force
Authors: Krappe Hans J.
Published: July 2002

The binding energy of a homogeneously charged, classical droplet is considered, whose charge elements interact via a Yukawa force. The six-dimensional self-energy integral is reduced to a three-dimensional integral for axially symmetric, but otherwise arbitrarily shaped, droplets. This integral is brought into a form particularly convenient for numerical calculations. Two integrals involving products of Bessel functions are evaluated, which are either not listed in standard tables of integrals or given in an erroneous form.
Some nodal theorems for noncentral forces
Authors: Levinger J. S.
Published: July 2002

Two lemmas are proved for local noncentral forces in multidimensional space. First, the lowest partial wave for the ground state is nodeless. Second, the lowest partial wave for the first excited state has at least one node. Ballot–Fabre de la Ripelle perturbation theory is also used to show that higher partial waves for the ground state have nodes near the positions of nodes (if any) in the corresponding element of the matrix element of the noncentral potential.
Exact symmetries of unidimensional self-similar flow
Authors: Gaffet B.
Published: July 2002

In addition to the symmetries that are known to apply to arbitrary flow, the self-similar equations may present other symmetries of their own. We present here such a symmetry of the self-similar unidimensional flow of an adiabatic inviscid fluid, with arbitrary polytropic index and arbitrary power-law entropy distribution. The new symmetry can be extended to the non-self-similar case if the flow is assumed isentropic. A connection with the theory of Riemann invariants is also discussed.
Dynamic systems driven by Markov processes
Authors: Korzeniowski Andrzej
Published: July 2002

Consider a differential equation Ẏ=V(X(t))Y(t), where X(t) is a random function. Sufficient conditions for asymptotic stability of the solution in terms of a generator of the stochastic process X(t) are given. The results are illustrated by several examples.
Path integral quantization of the dyonium
Authors: Dürr H. , Inomata A.
Published: July 2002

The dyonium is solved exactly by path integration. The Green’s function for the dyonium is separated into the monopole harmonics and the radial path integral, and the radial Green’s function is found in closed form. The exact energy spectrum is also obtained. Dirac’s charge quantization condition is seen to be essential for performing path integration.
Clifford- and Grassmann-like algebras—Old and new
Authors: Kwasniewski A. K.
Published: July 2002

Algebra extensions of Γ=Zk⊕⋅⋅⋅⊕Zk (n summands) are considered as old Clifford-like algebras. Grassmann-like algebras closely related to them are introduced. New Clifford-like and another Grassmann-like algebras are defined and discussed, the generalization consisting in considering k-linear structures instead of only bilinear ones. Several applications are listed.
Mixed supertableaux of the superunitary groups. II. SU(n‖m)
Authors: Delduc F. , Gourdin M.
Published: July 2002

The Young supertableaux of the superunitary groups are studied. We give the conditions on the size of legal supertableaux, the type of atypicity for tensor representations which are irreducible, making the link between the Kac–Dynkin parameters and those of the supertableau. A discussion is given on nonfully reducible representations and generalized atypical supertableaux.
Differential-Stäckel matrices
Authors: Kalnins E. G. , Miller Willard
Published: July 2002

We show that additive separation of variables for linear homogeneous equations of all orders is characterized by differential-Stäckel matrices, generalizations of the classical Stäckel matrices used for multiplicative separation of (second-order) Schrödinger equations and additive separation of Hamilton–Jacobi equations. We work out the principal properties of these matrices and demonstrate that even for second-order Laplace equations additive separation may occur when multiplicative separation does not.
Finite-dimensional representations of the Lie superalgebra sl(1,3) in a Gel’fand–Zetlin basis. I. Typical representations
Authors: Palev Tchavdar D.
Published: July 2002

In a series of two papers all finite-dimensional irreducible representations of the special linear Lie superalgebra sl(1,3) are constructed. Explicit formulas for the generators in an orthonormal Gel’fand–Zetlin basis of the even subalgebra gl(3) are given. This paper develops a background for constructing the representations. Expressions for the transformation properties of the basis under the action of the generators are written down within all typical sl(1,3) modules.
A class of solutions of the Einstein–Maxwell equations
Authors: Bajer Konrad , Kowalczyński Jerzy Klemens
Published: July 2002

We present all the exact solutions of the Einstein–Maxwell equations for a special case of the Robinson–Trautman metric form. Gaussian curvature of the angularlike part of the chosen metric form is equal to zero. The solutions are of the Petrov types D or II. Eight of them are probably new.
Relativistic quantum theory of fermions based on the Clifford algebra C7
Authors: Basri S. A. , Barut A. O.
Published: July 2002

A relativistic quantum theory of spin- 1/2 fermions is presented that includes a charge algebra, as well as an operator that distinguishes between leptons and baryons. This, in effect, extends the Clifford algebra C4 of Dirac’s γ matrices to C7. Moreover, the particle states Ψ are represented here by elements of C7 as products of projection operators, instead of column vectors. A number of important results are derived, and the theory serves as a foundation for constructing physical particle states as tensor products of the bare fermion states.
A new spin- 1/2 wave equation
Authors: Nash Patrick L.
Published: July 2002

A su(2)⊂so(3,1)⊂so(3,3) spin Casimir operator is shown to equal a sl(2,R) Casimir operator. This sl(2,R) Casimir operator may be factored to yield a wave equation describing a massive spin- 1/2 particle. This wave equation possesses only timelike momentum solutions, of both positive and negative energy. Moreover, the expectation value of the electric dipole moment, with respect to these solutions, vanishes in a rest frame of the particle.
The global existence of time-dependent vortex solutions
Authors: Burzlaff Jürgen , Moncrief Vincent
Published: July 2002

We study the Cauchy problem for Abelian Yang–Mills–Higgs theory in (2+1)-dimensional Minkowski space-time. With suitable conditions on the background fields and a suitable choice of a Sobolev space for the subtracted gauge potentials and the Higgs field, we establish local existence. We then prove global existence by showing that an appropriate norm of the solutions cannot blow up in a finite time, and discuss the topology of these solutions.
Evaluation of a class of integrals that arise in certain path integrals
Authors: Nash Patrick L.
Published: July 2002

A commonly encountered n-dimensional integral associated with a relativistic quadratic Lagrangian is explicitly evaluated for arbitrary n. In the limit n→∞, this integral is given by the usual Van Vleck–Morette determinant. The main advantage of the present approach is that it is simple and direct.
A unified treatment of Wigner 𝒟 functions, spin-weighted spherical harmonics, and monopole harmonics
Authors: Dray Tevian
Published: July 2002

A unified, self-contained treatment of Wigner 𝒟 functions, spin-weighted spherical harmonics, and monopole harmonics is given, both in coordinate-free language and for a particular choice of coordinates.
Verma bases for representations of classical simple Lie algebras
Authors: Li Sai-Ping , Moody R. V. , Nicolescu M. , Patera J.
Published: July 2002

Complete bases are constructed for all finite-dimensional irreducible representations of the simple Lie algebras over C of the types An (n≥1), Bn and Cn (2≤n≤6), Dn (4≤n≤6), and G2. Each basis vector is given as an explicit sequence of weight-lowering generators of the algebra acting on the highest weight vector of the representation space. A similar construction (due to D-N. Verma) for the highest weight representations of all Kac–Moody algebras of rank 2 is presented as well.
A complete determination of the zeros of weight-1 6j coefficients
Authors: Bremner Andrew , Brudno Simcha
Published: July 2002

It is shown how all zeros of weight-1 6j coefficients arise as particular cases of a four-parameter family of such zeros. The parametrization is given explicitly.
Classical and quantum scattering theory for linear scalar fields on the Schwarzschild metric. II
Authors: Dimock J. , Kay Bernard S.
Published: July 2002

An alternate treatment of the results of paper I is given. As in that paper, the Unruh boundary condition is formulated, the Unruh vacuum is defined as a state satisfying this boundary condition and the thermal character of the state is exhibited. The present work differs in that it uses the double-wedge region of the Kruskal manifold and defines and uses a precise notion of distinguished modes.