bluuebunny/crossref_metadata_2025 huggingface dataset:
Quartet and sextet states of CS−
Authors: Hochlaf M. , Chambaud G. , Rosmus P. , Andersen T. , Werner H. J.
Published: July 2002

The potential energy and spin–orbit functions have been calculated for several electronic states of CS and CS−. Comparison with experimental data for CS shows very good agreement, making reliable predictions possible for the CS− molecule such as the existence of long-lived metastable states. The a 4Σ−, b 4Π, and a 6Π states were found to lie energetically below the triplet or quintet states of the CS molecule. The calculated spin–orbit integrals between the electronic states suggest that the depletion of the J=5/2 or 7/2 components in the Π states will mainly occur via weak interactions with the electron continuum wave.
Experimental and theoretical ab initio study of the influence of N-methylation on the dipole-bound electron affinities of thymine and uracil
Authors: Desfrançois C. , Abdoul-Carime H. , Carles S. , Périquet V. , Schermann J. P. , Smith Dayle M. A. , Adamowicz Ludwik
Published: July 2002

The influence of N-methylation on the dipole-bound electron affinities of pyrimidine nucleic acid bases, uracil and thymine, has been investigated theoretically using ab initio quantum mechanical calculations, and experimentally using Rydberg electron transfer spectroscopy. Both experiment and theory are consistent in showing that replacement of hydrogen atoms by methyl groups reduces electron affinities corresponding to formation of dipole-bound anions of these systems. Also, the distortion of the anion geometries with respect to the geometries of the neutral parents are reduced with the methylation.
Gradients for the similarity transformed equation-of-motion coupled-cluster method
Authors: Gwaltney Steven R. , Bartlett Rodney J. , Nooijen Marcel
Published: July 2002

A derivation of gradients for the similarity transformed equation-of-motion coupled-cluster singles and doubles method is presented. Algebraic operator equations for all of the terms which appear in the equations are given, with a discussion about the procedure for solving the equations.
Effects of excited state mixing on transient absorption spectra in dimers: Application to photosynthetic light-harvesting complex II
Authors: Valkunas Leonas , Cervinskas Vilmantas , Trinkunas Gediminas , Müller Marc G. , Holzwarth Alfred R.
Published: July 2002

The excited state mixing effect is taken into account considering the difference spectra of dimers. Both the degenerate (homo) dimer as well as the nondegenerate (hetero) dimer are considered. Due to the higher excited state mixing with the two-exciton states in the homodimer, the excited state absorption (or the difference spectrum) can be strongly affected in comparison with the results obtained in the Heitler–London approximation. The difference spectrum of the heterodimer is influenced by two resonance effects (i) mixing of the ground state optical transitions of both monomers in the dimer and (ii) mixing of the excited state absorption of the excited monomer with the ground state optical transition in the nonexcited monomer. These effects have been tested by simulating the difference absorption spectra of the light-harvesting complex of photosystem II (LHC II) experimentally obtained with the 60 fs excitation pulses at zero delay times and various excitation wavelengths. The pairs of coupled chlorophylls a and b for simulations have been taken from the best LHC II assignment model obtained by simulating the steady-state spectra and the transient absorption at various excitation wavelengths. Qualitatively the spectral peculiarities of the difference spectra are explained by means of the resonance interpigment interactions, which are responsible for the excited state mixing.
A perturbation theory for solvation thermodynamics: Dipolar–quadrupolar liquids
Authors: Matyushov Dmitry V. , Voth Gregory A.
Published: July 2002

The thermodynamics of solvation of a dipole in hard sphere solvents with dipoles and quadrupoles is studied by using the Padé approximation for the perturbation expansion of the solvation chemical potential and compared to Monte Carlo simulations. Solvation chemical potentials, energies, and entropies of solvation are obtained at different dipolar and quadrupolar solvent strengths. The effect of nonlinear solvation is analyzed and found not to exceed 10% in the parameter range studied. An agreement between the simulations and the analytical theory is obtained by an empirical rescaling of the triple perturbation integrals of the perturbation expansion. This rescaling does not, however, provide a quantitatively correct partitioning of the solvation free energy into the energy and entropy of solvation.
Optical Kerr-effect investigation of the reorientational dynamics of CS2 in CCl4 solutions
Authors: Idrissi A. , Ricci M. , Bartolini P. , Righini R.
Published: July 2002

The reorientational relaxation of CS2 in solution in CCl4 and its dependence on both concentration and temperature is investigated with the use of the optical Kerr effect (OKE). The comparison of the single-particle reorientational relaxation time extracted from OKE data and obtained by Raman spectroscopy supports the hypothesis that the vibrational and reorientational relaxation processes for CS2 are not correlated. It is shown that the reorientational dynamics of CS2 is influenced by the solvent configuration around the solute molecule (cage effect), and that it is also influenced by the pair orientational correlation between solute molecules, even in dilute solutions.
Detection of the onset of demixing in simulations of polypropylene melts in which the chains differ only in stereochemical composition
Authors: Haliloglu Türkan , Mattice Wayne L.
Published: July 2002

Simulations have been performed at 480 K for pure melts of atactic, isotactic and syndiotactic polypropylene chains with a degree of polymerization of 50 and composition C150H302, and also for the three 50:50 mixtures of two of these species. The simulations are performed on a high coordination lattice, with incorporation of short range intramolecular interactions from a rotational isomeric state model of polypropylene, and incorporation of long range interactions defined by a Lennard-Jones potential energy function for the interaction of pairs of molecules of propane. Both the rotational isomeric state model and Lennard-Jones parameters were taken directly from the literature (Suter et al. and Prausnitz, respectively). The efficiency of the simulation on the sparsely occupied high coordination lattice facilitates the equilibration of the one- and two-component melts within accessible computer time. Onset of a tendency for demixing of isotactic and syndiotactic polypropylene is apparent in the intermolecular pair correlation functions. No such demixing occurs with isotactic and atactic polypropylene. Both of these predictions from the simulation are consistent with experimental results in the literature (Maier et al. and Lohse, respectively). The simulation produces an ambigious prediction for the melt of atactic and syndiotactic polypropylene. This melt has been reported (Maier et al.) to exhibit phase separation, but less strongly than the isotactic-syndiotactic system, for which the simulation makes an unambiguous (and correct) prediction. The physical origin of the tendency for demixing in the simulations is identified as the differences in the preferred local conformations of polypropylene chains with various stereochemical sequences. This driving force is an example of “conformational asymmetry” induced solely by differences in stereochemical sequence.
A stochastic study of microsolvation. I. Structures of CO in small argon clusters
Authors: Paesani F. , Gianturco F. A. , Lewerenz M. , Toennies J. P.
Published: July 2002

Diffusion Monte Carlo (DMC) calculations of the intermolecular vibrational ground states of CO(Ar)n clusters with n=1–12, for CO v=0 are reported. The intermolecular degrees of freedom of the clusters are treated in full dimensionality and a pairwise additive potential surface is used in which the Ar–CO interaction is described by a recently developed scheme which combines density functional theory (DFT) with the long-range dispersion contributions obtained from the perturbative theory. The calculations yield intermolecular ground state energies, Ar density distributions, radial and angular density probability distributions. Optimal structures by Simplex minimization have been calculated to estimate zero point energy (ZPE) and quantum effects.
High resolution absorption spectroscopy of the ν1=2–6 acetylenic overtone bands of propyne: Spectroscopy and dynamics
Authors: Campargue A. , Biennier L. , Garnache A. , Kachanov A. , Romanini D. , Herman M.
Published: July 2002

The rotationally resolved nν1 (n=2–6) overtone transitions of the CH acetylenic stretching of propyne (CH3–C≡C–H) have been recorded by using Fourier transform spectroscopy (n=2), various intracavity laser absorption spectrometers (n=3, 4, and 6) and cavity ring down spectroscopy (CRDS) (n=5). The 2ν1, 3ν1, and 6ν1 bands exhibit a well-resolved and mostly unperturbed J-rotational structure, whose analysis is reported. The 5ν1 band recorded by pulsed CRDS shows an unresolved rotational envelope. In the region of 12 700 cm−1, an anharmonic interaction is confirmed between 4ν1 and 3ν1+ν3+ν5. The band at a higher wave number in this dyad exhibits a partly resolved K-structure, whose analysis is reported. The mixing coefficient of the two interacting states is determined consistently using different procedures. The 1/35 anharmonic resonance evidenced in the 4ν1 manifold induces weaker intensity borrowing from the 2ν1 and 3ν1 levels to the ν1+ν3+ν5 and 2ν1+ν3+ν5 level, respectively, which have been predicted and identified. Several hot bands around the 2ν1, 3ν1, and 3ν1+ν3+ν5 bands arising from the ν9=1 and ν10=1 and 2 bending levels are identified and rotationally analyzed, also leading to determine x1,9 [−20.3(3) cm−1], x1,10 [−1.7975(75) cm−1], and x3,10 [−6.56 cm−1]. The J-clumps of the P and R branches in the 6ν1 band at 18 499 cm−1 show a Lorentzian homogeneous profile mostly J-independent with an average full width at half maximum (FWHM) of 0.17 cm−1, attributed to arising from the intramolecular vibrational energy redistribution towards the bath of vibrational states. A detailed comparative examination of the fine structure in all investigated nν1 (n=2 to 7) overtone bands and the similar behavior of the cold and hot bands arising from ν10=1 definitively suggests that a highly specific low-order anharmonic coupling, still unidentified, dominates the hierarchy of interaction mechanisms connecting the nν1 levels to the background states.
Mean first passage times of Brownian rotators from differential recurrence relations
Authors: Coffey W. T.
Published: July 2002

An exact method of calculation of mean first passage times (analogous to that previously used [W. T. Coffey, Yu. P. Kalmykov, E. S. Massawe, and J. T. Waldron, J. Chem. Phys. 99, 4011 (1993)] for the correlation time) is developed in terms of continued fractions from the zero frequency limit of the Laplace transform of the set of differential recurrence relations generated by the Fokker–Planck or Langevin equations. The method because it is based on a Floquet representation avoids the use of quadratures and so may be easily generalized to multidegree of freedom systems by the use of matrix continued fractions. The procedure is illustrated by considering the mean first passage time of a fixed axis rotator with two equivalent sites.
Rearrangements and tunneling splittings of protonated water trimer
Authors: Wales David J.
Published: July 2002

Stationary points and rearrangement mechanisms are characterized for protonated water trimer using a variety of basis sets and density functional theory to describe electron correlation. For the largest basis sets there are three distinct low-lying minima separated in energy by only a few wave numbers. Ten distinct transition states were found with barriers spanning nearly three orders of magnitude. Several of these mechanisms should produce observable tunneling splittings.
Calculation of the total energy per unit cell and of the band structures of the five nucleotide base stacks using the local-density approximation
Authors: Zhang M.-L. , Miao M. S. , Van Doren V. E. , Ladik J. J. , Mintmire J. W.
Published: July 2002

All-electron first-principles total energy electronic structure calculations were carried out for single chains of four nucleotide base stacks (composed of adenine, thymine, guanine, and cytosine, respectively) in the DNA B conformation (3.36 Å stacking distance and 36° screw angle θ) using the local-density approximation (LDA) within a helical band structure approach. A uracil stack was also computed in the DNA B conformation and compared with the results obtained for the four DNA base stacks. The total energies per unit cell as a function of the stacking distance (at fixed screw angle θ=36°) and of the screw angle (at d=3.36 Å) show in most cases rather good agreement with the experiment. As expected with LDA calculations, the band gaps were underestimated by nearly 50% compared to experimentally suggested values. Finally, some suggestions are given for the improvement of the band structures of the nucleotide base stacks.
Dissipative quantum dynamics in discrete energy representation: Photon-stimulated desorption of NO from metals
Authors: Guo Hua , Ma Guobin
Published: July 2002

Desorption induced by single and multiple electronic transitions is described by a reduced density matrix formulation in a discrete energy representation. The discrete energy basis is comprised of the eigenfunctions of the system Hamiltonian augmented by an asymptotic potential wall, and has a number of advantages over its coordinate counterpart, such as the minimization of the basis size. The Liouville–von Neumann equation of a Lindblad semigroup form is solved numerically using a short-time Chebyshev propagation scheme. The dynamics of NO photodesorption from metals is investigated with one-dimensional two-state models corresponding to both the Menzel–Gormer–Redhead and Antoniewicz mechanisms. Desorption stimulated by both weak cw and strong pulsed light sources are examined.
Dynamics and energy release in benzene/Ar cluster dissociation
Authors: Bernshtein V. , Oref I.
Published: July 2002

Energy disposal distributions and cluster lifetimes of Ar–benzene clusters (ABC) were studied by quasiclassical trajectory calculations. Four intermolecular potentials, Lennard-Jones, ab initio, and two Buckingham-type potentials, were used in the calculations. The Ar atom was placed in one of the five minima of the potential surface at 0 K. The benzene monomer in ABC at 0 K was excited to various internal energies, and internal energy loss of the monomer following dissociation was calculated. The average energy removed, 〈ΔE〉, depends on the well depth of the potential and on the initial structure of the cluster. The highest value was obtained when the cluster was formed at the deepest well, in which the Ar atom is above the center of the ring. Regardless of the initial structure, it was found that the atom migrated from well to well including the deepest, and dissociation occurred from a structure different from the initial one. No correlation was found between the energy removed and the cluster lifetime, i.e., the dissociation process is history independent. Rotations and out-of-plane vibrations play a major role in the dissociation process. Except for the lowest values of ΔE, the energy disposal probability density function, P(E′,E), is exponential in ΔE. The cluster lifetime distributions depend on the potential, and can be fit by multiexponential functions. Within a given potential, the shallower the well the narrower the temporal distribution, and the higher the internal energy of ABC the shorter the lifetime. Application of Rice–Ramsperger–Kassel–Marcus (RRKM) theory to cluster modes, which contain an amount of energy ΔE, yields lifetimes with values similar to those obtained directly from trajectory calculations. A comparison is made between P(E′,E), 〈ΔE〉, and lifetimes obtained in cluster-dissociation and gas-phase collision calculations for identical inter- and intramolecular potentials. Energy transfer quantities and lifetimes are larger in clusters, while the mechanism of energy transfer and the contribution to it of rotations and out-of-plane vibrations are similar in both systems.
The electronic structure and spectroscopy of V2
Authors: O’Brien Ted A , Albert Katrin , Zerner Michael C.
Published: July 2002

The electronic structure and spectroscopy of the vanadium dimer has been studied with semiempirical self-consistent field-configuration interaction calculations using the intermediate neglect of differential overlap Hamiltonian parameterized for spectroscopy (INDO/S) including spin–orbit coupling effects. An approximate configuration interaction (CI) treatment is designed based on correlation effects observed in CI calculations in small active spaces, and yields good agreement with experimental observations of state energies and spin-orbit splittings. The location of a 1Σg+ excited state isoconfigurational with the ground state was determined, and calls into question a previous assignment of an excited state observed near 1860 cm−1. The previously observed A 3Πu←X 3Σg− transition is assigned as a dδg←dπu promotion. In addition, an unassigned transition observed near 15 000 cm−1 has been assigned as B 3Σu−←X 3Σg−. Both this transition and the previously observed A′ 3Σu−←X 3Σg− transition are assigned as σu←σg promotions, in disagreement with previous assignments. A 1Σu+ state isoconfigurational with the A′ 3Σu− state is suggested as a candidate for an unassigned transition in the range 11 250–12 500 cm−1.
Self-consistent harmonic theory of solvation in glassy systems: Quantum solvation
Authors: Reichman David R. , Voth Gregory A.
Published: July 2002

The self-consistent harmonic theory developed in the preceding paper for the study of classical solvation dynamics in glassy media is extended to treat quantum solvation. In particular, a quantum set of optimized normal modes and a methodology for calculating, quantum mechanically, all multiphonon contributions to solvation are presented. The simulation of solvation dynamics in a low temperature glass shows nontrivial quantum effects. The relationship between the quantum theory presented in this work and previous theories is discussed.
The effects of a dynamic lattice on methane self-diffusivity calculations in AlPO4-5
Authors: Thomson Kendall T. , McCormick Alon V. , Ted Davis H.
Published: July 2002

Canonical ensemble molecular dynamics simulations were conducted for methane diffusion in AlPO4-5 in order to assess the role of the lattice motion on adsorbate diffusivity in straight pore zeolites. Both a static lattice model and a full dynamic lattice model were used at a loading of 1.5 methane/unit cell at 295 K. Although recent simulation work has asserted that there should be a difference, we show that there is little difference in the observed methane diffusivity (1.26×10−7 m2/s) and passing frequency (0.305) when a static lattice approximation is used over a full dynamic lattice (1.33×10−7 m2/s and 0.328). Furthermore, we introduce a methodology for handling lattice motion in molecular simulations by utilizing the normal vibrational modes in a harmonic crystal approximation.
A density functional theory based on the universality of the free energy density functional
Authors: Zhou Shiqi , Ruckenstein Eli
Published: July 2002

A methodology for classical density functional theory is proposed which expresses the first order direct correlation function for nonuniform systems in terms of the second order direct correlation function and the bridge function of the corresponding uniform systems. Its applicability to nonuniform systems is verified by applying the approach to three concrete cases, namely, to a hard sphere fluid in a spherical cavity, a hard sphere fluid near a hard wall, and a hard sphere fluid near a 9–3 soft wall. The present density functional theory (DFT) provides a recipe by which the integral equation theories for uniform systems can be transformed into the corresponding DFTs for nonuniform systems.
Dynamics of I*(2P1/2) production from fluorinated alkyl iodides at 266, 280, and ∼305 nm
Authors: Kavita K. , Das Puspendu K.
Published: July 2002

In this paper, we present I*(2P1/2) quantum yield, φ* from the gas phase photodissociation of a series of perfluoroalkyl iodides at three different wavelengths 266, 280, and ∼305 nm. The iodine atoms in the ground I(2P3/2) and spin–orbit excited I*(2P1/2) states were monitored directly by a two photon laser induced fluorescence scheme. The I* quantum yields for the fluorinated alkyl iodides are found to be much higher than their corresponding alkyl iodide analogs over the entire A band. However, φ* remains more or less unchanged as a function of photolysis wavelength for the perfluoroalkyl iodides with the exception of CF3I in which it drops monotonically as a function of wavelength. Unlike in normal alkyl iodides, branching at the α position does not affect the φ* in perfluoroalkyl iodides. The prediction of I* yield using the one dimensional Landau–Zener soft-radical-impulse model is opposite to what is seen from our measurements. In all the fluorinated alkyl iodides, the CF3 in-plane rocking mode which can take the initially excited Q03 state to the Q11 state through the crossing region appears to be weakly coupled to the C–I stretch resulting in low yield of I atom in the dissociation process.
A combined instantaneous normal mode and time correlation function description of the optical Kerr effect and Raman spectroscopy of liquid CS2
Authors: Ji Xingdong , Ahlborn Heather , Space Brian , Moore Preston B. , Zhou Y. , Constantine S. , Ziegler L. D.
Published: July 2002

The depolarized reduced Raman and corresponding optical Kerr effect (OKE) spectral density of ambient CS2 have been calculated by way of time correlation function (TCF) and instantaneous normal mode (INM) methods and compared with experimental OKE data. When compared in the reduced Raman spectrum form, where the INM spectrum is proportional to the squared polarizability derivative weighted density of states (DOS), the INM results agree nearly quantitatively (at all but the lowest frequencies) with the TCF results. Both are in excellent agreement with experimental measurements. The INM signal has a significant contribution from the imaginary INMs. Within our INM theory of spectroscopy the imaginary INMs contribute like the real modes, at the magnitude of their imaginary frequency. When only the real modes are allowed to contribute, and the spectrum is rescaled to account for the missing degrees of freedom, the results are much poorer, as has been observed previously. When the spectra are compared in their OKE form, the INM spectrum is found to lack the low-frequency spike which is associated with long time scale rotational diffusion, and it is not surprising that an INM theory would not capture such a feature. The results demonstrate that while the OKE and spontaneous depolarized Raman spectrum contain the same information, they clearly highlight different dynamical time scales. At higher frequencies (ω>25 cm−1) the INM OKE results are in excellent agreement with TCF and experimental results. The TCF results capture the low-frequency spike and are in agreement with experiment everywhere within the precision of the present calculations. The molecular contributions to the OKE signal are analyzed using INM methods.
Parallel filter diagonalization: A novel method to resolve quantum states in dense spectral regions
Authors: Santra R. , Breidbach J. , Zobeley J. , Cederbaum L. S.
Published: July 2002

A parallel version of D. Neuhauser’s filter diagonalization algorithm is presented. In contrast to the usual procedure of acting with a set of narrow filter operators on a single or just a few initial vectors, parallelizability is achieved by working with a single, broad filter operator and a correspondingly large number of initial vectors. Apart from the obvious speedup in computation time, there is no need for communication between the processors involved in the computation. Furthermore, because a significantly reduced number of matrix vector multiplications is needed per initial vector, parallel filter diagonalization is numerically more stable than the single processor approach. It is argued that this method is particularly attractive for calculating eigenvectors of the large-scale secular matrices arising in quantum chemistry, especially in dense spectral regions. An application to dense state distributions of a cationic molecular cluster serves as an illustrative example. This is the first time filter diagonalization is used as a tool for ab initio electronic structure calculations.
The silaketenylidene (SiCO) molecule: Characterization of the X̃ 3Σ− and Ã 3Π states
Authors: Petraco Nicholas D. K. , Brown Shawn T. , Yamaguchi Yukio , Schaefer Henry F.
Published: July 2002

The ground (X̃ 3Σ−) and first excited triplet (Ã 3Π) electronic states of carbonylsilene or silaketenylidene, SiCO, have been investigated systematically using ab initio electronic structure theory. The total energies and physical properties including equilibrium geometries, dipole moments, harmonic vibrational frequencies, and associated infrared (IR) intensities were predicted using self-consistent-field (SCF), configuration interaction with single and double excitations (CISD), coupled cluster with single and double excitations (CCSD), equation-of-motion (EOM) CCSD, CCSD with perturbative triple excitations [CCSD(T)] methods with a wide range of basis sets. The linear X̃ 3Σ− ground state of SiCO has a real degenerate bending vibrational frequency, whereas the Ã 3Π state of SiCO is subject to the Renner–Teller effect and presents two distinct real vibrational frequencies along the bending coordinate. The bending vibrational frequency of the Ã 3Π state was evaluated via the EOM-CCSD technique. At the highest level of theory with the largest basis set, cc-pVQZ CCSD(T), the adiabatic X̃–Ã splitting without the zero-point vibrational energy (ZPVE) correction (Te value) was determined to be 68.5 kcal/mol (2.97 eV, 23 900 cm−1) and the adiabatic splitting with the ZPVE energy correction (T0 value) to be 69.0 kcal/mol (2.99 eV, 24 100 cm−1), which are in excellent agreement with the experimental T0 value of 68.78 kcal/mol (2.983 eV, 24 056 cm−1). The theoretical ground state harmonic Si–C stretching frequency ω3=564 cm−1 is much less than the experimental estimate of 800 cm−1.
Thermal excitation of rotation of the methyl group in chemisorbed acetate on Cu(110)
Authors: Lee J.-G. , Ahner J. , Mocuta D. , Denev S. , Yates J. T.
Published: July 2002

The adsorption of acetic acid on the Cu(110) surface has been investigated by the time-of-flight electron stimulated desorption ion angular distribution technique by observing H+(D+) ions from the methyl groups. The activated conversion of acetic acid to acetate has been witnessed by observing the formation of oriented acetate species. It has been found that the activation energy for acetate formation varies from 0.39±0.06 eV at low coverage to 1.1±0.1 eV at high coverage, possibly because of acetic acid stabilization at high coverage by hydrogen bonding. Methyl groups are oriented with one C–H bond azimuthally directed in the 〈11̄0〉 direction. At high coverage, the methyl groups are tilted slightly in the 〈11̄0〉 direction due to repulsive acetate–acetate interactions. The activated rotation of the methyl groups on adsorbed acetate is clearly observed by the electron stimulated desorption ion angular distribution method and the barrier height for CH3 rotation is estimated to be 12±6 meV, and for CD3 groups to be 7±4 meV. The small inverse D isotope effect is postulated to be caused by higher amplitude CH3 wagging motions compared to CD3, which permit slightly higher hyperconjugation for CH3 as this group interacts with the anchoring carboxyl group.
Basis sets in correlated effective potential calculations
Authors: Christiansen P. A.
Published: July 2002

Due to the behavior of the pseudo-orbitals near nuclei, basis set selection in shape-consistent effective potential calculations can be problematic in studies using correlation techniques based on virtual orbital expansions (configuration interaction, etc.). In this paper we quantify the magnitude of the problem and give simple rules for the selection of correlating functions in a manner that parallels the use of simple diffuse primitives in all-electron work. Our calculations show the problem to be substantial for s and p basis sets, and to involve both one- and two-center effects, but is negligible for higher l. We also show that the problems can be avoided by the inclusion of one additional high exponent s primitive in the basis set and by augmenting p primitives with a higher exponent function so as to give zero first derivatives at the nucleus. By this recipe, computed s and p shell correlation energies in single and double promotion configuration interaction calculations can be increased by 3%–7%, as compared to basis sets using simple diffuse primitives for correlation.
An atomically detailed description of metal–dielectric interfaces: The crossover from surface to bulk conducting properties of Ag–Xe
Authors: Shah Vaishali , Bowen H. F. , Space Brian
Published: July 2002

An atomically detailed simulation method designed to be efficacious for modeling conduction properties of closed shell atoms or molecules resident at interfaces that was developed earlier is applied to a metal–dielectric interface of Ag–Xe. The effective mass of conduction electrons resident at Ag–Xe interfaces as a function of the number of layers of xenon present has been measured experimentally by the Harris group [J. D. McNeill, R. L. Lingle, Jr., R. E. Jordan, D. F. Padowitz, and C. B. Harris, J. Chem. Phys. 105, 3883 (1996)]. Here a simple yet effective theoretical model of the interface is developed and the effective mass that results is in quantitative agreement with the empirical measurements. The effective mass of a conduction electron is calculated by solving the Schrödinger–Bloch equation using Lanczos grid methods to obtain the Bloch wave vector (k) dependent energies. The metal is treated as a continuum within the effective mass approximation for the purpose of calculating the eigenenergies. To model the explicit potential energy functions, the electron–atom interaction is taken as a local pseudopotential that is fit to simultaneously reproduce the experimentally measured gas phase s-, p-, and d-wave scattering phase shifts. In simulating the interfacial environment the potential energy interaction between the electron and xenon atoms is modified to account for many-body polarization effects. This approach shows promise in modeling the conduction properties of more complex interfacial environments, including those of technological interest.
A path integral ground state method
Authors: Sarsa A. , Schmidt K. E. , Magro W. R.
Published: July 2002

Ground state expectation values are obtained by using a path integral ground state Monte Carlo method. The method allows calculations of ground state expectation values without the extrapolations often used with Green’s function and diffusion Monte Carlo methods. We compare our results with those of Green’s function Monte Carlo by calculating some ground state properties of the van der Waals complex He2Cl2 as well as the infinite systems liquid and solid He4. Advantages and disadvantages of the present method with respect to previous ones are discussed.
Comment on “Anisotropic intermolecular interactions in van der Waals and hydrogen-bonded complexes: What can we get from density-functional calculations?” [J. Chem. Phys. 111, 7727 (1999)]
Authors: Wesol/owski Tomasz A.
Published: July 2002

In this comment, it is pointed out that the generalized gradient approximation (GGA) functionals considered by Milet et al. [ J. Chem. Phys. 111, 7727 (1999)] share the same exchange part (B88) which violates significantly the Lieb–Oxford bound. Violation of this exact condition was shown to result in significant errors of the exchange energy in the case of weakly overlapping electron densities [Wesol/owski et al., J. Phys. Chem. A 101, 7818 (1997); Zhang et al., J. Chem. Phys. 107, 7921 (1997)]. Numerical examples are given to illustrate that such exchange functionals which better satisfy the Lieb–Oxford bound lead to better interaction energies also for the complexes studied by Milet et al.
Classical mechanical photon echo of a solvated anharmonic vibration
Authors: Williams Ryan B. , Loring Roger F.
Published: July 2002

The vibrational photon echo measurement employs short pulses of coherent infrared radiation to discriminate among line broadening processes of different time scales. The measurement has been analyzed with the optical Bloch equations, in which the coupling of a quantum three-level system to a bath is represented by dephasing times. A detailed treatment of vibrational dynamics in a molecular liquid requires a Hamiltonian model. As such models are more readily treated in classical than in quantum mechanics, we consider the calculation of the vibrational echo in classical mechanics. Vibrational echoes are calculated for a solvated anharmonic oscillator. The classical mechanical echo is shown to share attributes of a quantum mechanical calculation.
Lie algebras for systems with mixed spectra. I. The scattering Pöschl–Teller potential
Authors: Frank Alejandro , Wolf Kurt Bernardo
Published: July 2002

Starting from an N-body quantum space, we consider the Lie-algebraic framework where the Pöschl–Teller Hamiltonian, − 1/2 ∂2χ +c sech2 χ+s csch2 χ, is the single sp(2,R) Casimir operator. The spectrum of this system is mixed: it contains a finite number of negative-energy bound states and a positive-energy continuum of free states; it is identified with the Clebsch–Gordan series of the 𝒟+×𝒟− representation coupling. The wave functions are the sp(2,R) Clebsch–Gordan coefficients of that coupling in the parabolic basis. Using only Lie-algebraic techniques, we find the asymptotic behavior of these wave functions; for the special pure-trough potential (s=0) we derive thus the transmission and reflection amplitudes of the scattering matrix.
Extension of Wick’s theorem by means of the state operator formalism
Authors: Nomura Masao
Published: July 2002

Reordering of operators in the second quantization formalism is described by using state operators as basic operators, where the state operator is either a cluster of creation operators or that of annihilation operators specified by a set of quantum numbers of any representation. The commutation relation between state operators is simply expressed in terms of the coefficient of fractional parentage (cfp), the factor specific to state operator (de) composition. Wick’s theorem, prevalently applied to a string of creation and annihilation operators, is extended to a string of state operators. Similar extension is done for the contraction theorem.
The statistics of interacting dumbbells on a 2×N lattice space
Authors: Walikainen D. , McQuistan R. B.
Published: July 2002

A set theoretic argument is utilizied to determine a 31-term recursion that describes exactly the composite nearest-neighbor degeneracy for indistinguishable dumbbell particles distributed on a rectangular 2×N lattice space. The associated generating functions, the expectation of the lattice coverage, and the density of occupied nearest-neighbor pairs are also determined.
A technique for evaluation of the strong potential Born approximation for electron capture
Authors: Sil N. C. , McGuire J. H.
Published: July 2002

A technique is presented for evaluating differential cross sections in the strong potential Born (SPB) approximation. Our final expression is expressed as a finite sum of one-dimensional integrals, expressible as a finite sum of derivatives of hypergeometric functions.
Spinors as fundamental objects
Authors: Budinich Paolo , Bugajska Krystyna
Published: July 2002

We define, on the algebraic Dirac spinor space Ψ, some operators D± and T±. By means of them we show how the fundamental operations of Hermitian conjugation, complex conjugation, bar conjugation, and so on may be introduced in the Clifford algebra approach. These definitions depend on the geometrical property of the pure imaginary unit i of the Dirac algebra Ds,t and are the same only for mod 4 dimensions of vector space-times Rs,t. Furthermore, on the set Ψ×Ψ we introduce equivalence relations R± and define bijections χ± between Ψ×Ψ/R± and Ds,t. We investigate some properties of χ± and give the necessary and sufficient conditions for u∈Ds,t to belong to some minimal left ideal of Ds,t. Next we use the decomposition of the Dirac algebra Ds,t onto the Dirac spinor spaces to demonstrate two different ways of an action of any element s∈Spin(x,t). These considerations throw a new light onto the problem of the covariant derivative on the bundle of algebraic spinors over a space-time manifold.
A multitype random sequential process. II. Distribution of particle size and vacant space length in the saturation limit
Authors: Mellein B.
Published: July 2002

A one-dimensional lattice space of n equivalent compartments is filled sequentially at random with nonoverlapping particles of integral length β ( β-bell particles), the latter assumed to be a random variable with probability distribution { pq,...,pr} on { q,q+1,...,r−1,r}, q≥1. Due to configurational degeneracies the relative probability p*k,n of ultimately finding a k-bell particle on the saturated lattice space will generally not coincide with pk, the ‘‘input’’ probability. In the present paper we shall determine p*k,n, k=q,...,r, and its limit as n tends to infinity. Some more insight into the occupation configuration of the lattice space in the jammed state is gotten by means of the length distribution of stretches of unoccupied compartments (gaps).
Flow reversal symmetry in a convective heat exchange model
Authors: Pignotti Alberto
Published: July 2002

Under some simplifying assumptions often used in the thermal design of heat exchangers, a system of two coupled linear homogeneous first-order partial differential equations with variable coefficients is used to describe a steady-state convective heat exchange process. Using an integral representation for the outlet temperatures as functions of the inlet ones, a symmetry property is proved for the transformation that inverts the velocity fields of both fluids. In particular, the average thermal effectiveness is shown to coincide for the direct and reversed processes.
Baker–Campbell–Hausdorff relations for supergroups
Authors: Kostelecký V. Alan , Nieto Michael Martin , Truax Rodney
Published: July 2002

One-parameter subgroups, the exponential mapping, and canonical coordinates have previously been defined for connected supergroups. In this paper, a technique for obtaining analytical expressions linking different coordinate schemes for supergroups is presented. These are the Baker–Campbell–Hausdorff relations. The method is illustrated in detail with the examples of supergroups based on the supersymmetric quantum-mechanical superalgebra sqm (2) and on the Inönü–Wigner contraction isop(1/2) of the simple superalgebra osp(1/2).
Lorentz transformations in terms of initial and final vectors
Authors: van Wyk C. B.
Published: July 2002

Given arbitrary initial vector(s) and their final vector(s) in a Lorentz transformation, the problem is to determine the operator of the transformation. The solution presented here consists of expressing the tensor contained in the Lorentz operator in terms of the given vectors and then the operator itself follows by the exponentiation of a generating matrix. This is possible in certain special cases. In the general case a number of simultaneous nonlinear equations have to be solved. The analytical solution of these equations is elusive while attempts at numerical solution indicate that supplementary information is required. The corresponding procedure for a singular operator is also presented.
Gravitational anomalies in two dimensions: A cohomological approach
Authors: Bandelloni Giuseppe
Published: July 2002

The spectral sequences method is employed to study the cohomology space of the Becchi–Rouet–Stora (BRS) operator, which describes the general coordinate transformations in a two-dimensional polynomial Lagrangian field theory. A pure external gravitational model is considered. In the Fadeev–Popov charge-one sector, two classes of elements are found: the first represents the ordinary trace anomalies, in the second the presence of the anomalies recently calculated by Bardeen and Zumino are pointed out.
Symmetries and conserved quantities in geodesic motion
Authors: Hojman Sergio , Nuñez Luis , Patiño Alberto , Rago Hector
Published: July 2002

Recently obtained results linking several constants of motion to one (non-Noetherian) symmetry to the problem of geodesic motion in Riemannian space-times are applied. The construction of conserved quantities in geodesic motion as well as the deduction of geometrical statements about Riemannian space-times are achieved.
Field-diffeomorphism anomalies in the nonlinear σ model
Authors: Bandelloni Giuseppe
Published: July 2002

The field-diffeomorphism anomalies in the nonlinear σ model are explicitly discussed, using the spectral sequences technique. The role of the Riemannian constraints is analyzed for low space-time dimensions.
A class of self-dual solutions for SU(2) gauge fields on Euclidean space
Authors: Leaute Bernard , Marcilhacy Gilbert
Published: July 2002

By applying the method of separation of variables a particular class of solutions, depending on the four variables (xμ) of Yang’s equation in the R gauge for self-dual SU(2) gauge fields on Euclidean four-dimensional flat space, is obtained. These solutions are parametrized by a particular form of the fifth Painlevé transcendent. For a specific choice of certain constants, there is degeneration, and the solutions functionally depend on elementary functions.
Type-D rigidly rotating perfect fluid solutions
Authors: García D. Alberto , Hauser Isidore
Published: July 2002

Within the type-D Carter metric structure with a perfect fluid source, it is established that the Wahlquist metric and a new divergenceless solution are the only perfect fluid solutions satisfying positive energy and regularity conditions. The divergenceless solution, obtainable also as a limiting transition of the Wahlquist one, is endowed with three arbitrary parameters, and contains the Kramer fluid solution as a particular case. The fluid four-velocity of these metrics does not lie in the two-space spanned by the double principal null directions of the Weyl tensor.
Gauge theory of a group of diffeomorphisms. III. The fiber bundle description
Authors: Lord Eric A. , Goswami P.
Published: July 2002

A new fiber bundle approach to the gauge theory of a group G that involves space-time symmetries as well as internal symmetries is presented. The ungauged group G is regarded as the group of left translations on a fiber bundle G(G/H,H), where H is a closed subgroup and G/H is space-time. The Yang–Mills potential is the pullback of the Maurer–Cartan form and the Yang–Mills fields are zero. More general diffeomorphisms on the bundle space are then identified as the appropriate gauged generalizations of the left translations, and the Yang–Mills potential is identified as the pullback of the dual of a certain kind of vielbein on the group manifold. The Yang–Mills fields include a torsion on space-time.
Casimir operators for massless representations of the super-Poincaré algebra and the reduction of the ten-dimensional massless scalar superfield
Authors: Kwon P. , Villasante M.
Published: July 2002

Invariant operators for the massless little algebra of SPd (super-Poincaré algebra in d dimensions) are given. They are used to decompose the scalar (massless) superfield in ten dimensions. Explicit expressions for the irreducible pieces are obtained after exploiting a relevant Cartan subalgebra.
The nonexistence of the path-space measure for the Dirac equation in four space-time dimensions
Authors: Zastawniak Tomasz
Published: July 2002

It is proved that the path-space measure for the Dirac equation in four space-time dimensions does not exist. The origin of the nonexistence of the measure turns out to be the dependence of the solution on the first derivative of the initial condition.
New aspects of the path integrational treatment of the Coulomb potential
Authors: Castrigiano D. P. L. , Stärk F.
Published: July 2002

The well-known treatment of the path integral for the Coulomb potential, by means of the Kustaanheimo–Stiefel transformation and a time transformation, is made more transparent by reducing the problem to the equality of two measures on the space of paths. For this equality two proofs are given: an elementary computational one and a short one recurring to general features of stochastic processes. It is shown that the time transformation is a special case of the well-known time change for a continuous local martingale, by which the process is changed to a Brownian motion and which is determined by its quadratic variation.
Hyperfunction quantum field theory: Basic structural results
Authors: Brüning Erwin , Nagamachi Shigeaki
Published: July 2002

The choice of the class E′ of generalized functions on space-time in which to formulate general relativistic quantum field theory (QFT) is discussed. A first step is to isolate a set of conditions on E′ that allows a formulation of QFT in otherwise the same way as the original proposal by Wightman [Ark. Fys. 28, 129 (1965)], where E′ is the class of tempered distributions. It is stressed that the formulation of QFT in which E′ equals the class of Fourier hyperfunctions on space-time meets the following requirements: (A) Fourier hyperfunctions generalize tempered distributions thus allowing more singular fields as suggested by concrete models; (B) Fourier hyperfunction quantum fields are localizable both in space-time and in energy-momentum space thus allowing the physically indispensable standard interpretation of Poincaré covariance, local commutativity, and localization of energy-momentum spectrum; and (C) in Fourier hyperfunction quantum field theory almost all the basic structural results of ‘‘standard’’ QFT (existence of a PCT operator, spin-statistics theorems, existence of a scattering operator, etc.) hold. Finally, a short introduction to that part of Fourier hyperfunction theory needed in this context is given.
Kac–Moody algebra from infinitesimal Riemann–Hilbert transform
Authors: Chau Ling-Lie , Ge Mo-Lin
Published: July 2002

A general formulation is given for deriving a Kac–Moody algebra in the spectrum space from the infinitesimal regular Riemann–Hilbert transform. Such a Kac–Moody algebra can be obtained for many nonlinear systems, e.g., the (super) principal chiral model with or without a Wess–Zumino–Witten term, the sine-Gordon, Liouville, and KdV equations; reduced two-dimensional gravity (Belinski–Zakharov gravity), and self-dual supersymmetric Yang–Mills theories.
N=2 super Riemann surfaces and algebraic geometry
Authors: Falqui Gregorio , Reina Cesare
Published: July 2002

The geometric framework for N=2 superconformal field theories are described by studying susy2 curves—a nickname for N=2 super Riemann surfaces. It is proved that ‘‘single’’ susy2 curves are actually split supermanifolds, and their local model is a Serre self-dual locally free sheaf of rank two over a smooth algebraic curve. Superconformal structures on these sheaves are then examined by setting up deformation theory as a first step in studying moduli problems.