# Showing papers in "Journal of Chemical Physics in 1980"

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TL;DR: In this article, a contract Gaussian basis set (6•311G) was developed by optimizing exponents and coefficients at the Mo/ller-Plesset (MP) second-order level for the ground states of first-row atoms.

Abstract: A contracted Gaussian basis set (6‐311G**) is developed by optimizing exponents and coefficients at the Mo/ller–Plesset (MP) second‐order level for the ground states of first‐row atoms. This has a triple split in the valence s and p shells together with a single set of uncontracted polarization functions on each atom. The basis is tested by computing structures and energies for some simple molecules at various levels of MP theory and comparing with experiment.

12,620 citations

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TL;DR: In this article, the contracted Gaussian basis sets for molecular calculations are derived from uncontracted (12,8) and ( 12,9) sets for the neutral second row atoms, Z=11-18, and for the negative ions P−, S−, and Cl−.

Abstract: Contracted Gaussian basis sets for molecular calculations are derived from uncontracted (12,8) and (12,9) sets for the neutral second row atoms, Z=11–18, and for the negative ions P−, S−, and Cl−. Calculations on Na...2p63p, 2P and Mg...2p63s3p, 3P are used to derive contracted Gaussian functions to describe the 3p orbital in these atoms, necessary in molecular applications. The derived basis sets range from minimal, through double‐zeta, to the largest set which has a triple‐zeta basis for the 3p orbital, double‐zeta for the remaining. Where necessary to avoid unacceptable energy losses in atomic wave functions expanded in the contracted Gaussians, a given uncontracted Gaussian function is used in two contracted functions. These tabulations provide a hierarchy of basis sets to be used in designing a convergent sequence of molecular computations, and to establish the reliability of the molecular properties under study.

7,306 citations

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TL;DR: In this paper, it is shown that time averages of properties of the simulated fluid are equal to averages over the isoenthalpic-isobaric, canonical, and isothermal-isboric ensembles.

Abstract: In the molecular dynamics simulation method for fluids, the equations of motion for a collection of particles in a fixed volume are solved numerically. The energy, volume, and number of particles are constant for a particular simulation, and it is assumed that time averages of properties of the simulated fluid are equal to microcanonical ensemble averages of the same properties. In some situations, it is desirable to perform simulations of a fluid for particular values of temperature and/or pressure or under conditions in which the energy and volume of the fluid can fluctuate. This paper proposes and discusses three methods for performing molecular dynamics simulations under conditions of constant temperature and/or pressure, rather than constant energy and volume. For these three methods, it is shown that time averages of properties of the simulated fluid are equal to averages over the isoenthalpic–isobaric, canonical, and isothermal–isobaric ensembles. Each method is a way of describing the dynamics of a certain number of particles in a volume element of a fluid while taking into account the influence of surrounding particles in changing the energy and/or density of the simulated volume element. The influence of the surroundings is taken into account without introducing unwanted surface effects. Examples of situations where these methods may be useful are discussed.

4,564 citations

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TL;DR: In this article, general integral and series expressions are derived for the intensities of sidebands observed in the magic angle spectra of inhomogeneously broadened I = 1/2 systems.

Abstract: General integral and series expressions are derived for the intensities of sidebands observed in the magic angle spectra of inhomogeneously broadened I=1/2 systems The expressions are evaluated for a wide range of shift parameters and the results used to construct graphical and numerical methods for extracting the principal values of chemical shift tensors from the intensities of just a few sidebands The methods are illustrated by application to 31P spectra of barium diethyl phosphate The results agree well with previous single crystal measurements

1,438 citations

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TL;DR: In this paper, the authors derived the classical Hamiltonian of a polyatomic system in terms of these coordinates and their conjugate momenta for the general case of an N atom system with a given nonzero value of the total angular momentum.

Abstract: The reaction path on the potential energy surface of a polyatomic molecule is the steepest descent path (if mass‐weighted Cartesian coordinates are used) connecting saddle points and minima. For an N‐atom system in 3d space it is shown how the 3N‐6 internal coordinates can be chosen to be the reaction coordinate s, the arc length along the reaction path, plus (3N‐7) normal coordinates that describe vibrations orthogonal to the reaction path. The classical (and quantum) Hamiltonian is derived in terms of these coordinates and their conjugate momenta for the general case of an N atom system with a given nonzero value of the total angular momentum. One of the important facts that makes this analysis feasible (and therefore interesting) is that all the quantities necessary to construct this Hamiltonian, and thus permit dynamical studies, are obtainable from a relatively modest number of ab initio quantum chemistry calculations of the potential energy surface. As a simple example, it is shown how the effects o...

1,251 citations

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1,121 citations

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TL;DR: In this paper, the stable states picture (SSP) was used to derive the time correlation function (tcf) for the rate constant κ for a wide variety of gas and solution phase reaction models.

Abstract: The time correlation function (tcf) formulas for rate constants κ derived via the stable states picture (SSP) of chemical reactions are applied to a wide variety (a–d) of gas and solution phase reactionmodels. (a) For gas phase bimolecular reactions, we show that the flux tcf governing κ corresponds to standard numerical trajectory calculation methods. Alternate formulas for κ are derived which focus on saddle point surfaces, thus increasing computational efficiency. Advantages of the SSP formulas for κ are discussed. (b) For gas phase unimolecular reactions, simple results for κ are found in both the strong and weak coupling collision limits; the often ignored role of product stabilization is exposed for reversible isomerizations. The SSP results correct some standard weak coupling rate constant results by as much as 50%. (c) For barrier crossing reactions in solution, we evaluate κ for a generalized (non‐Markovian) Langevin description of the dynamics. For several realistic models of time dependent friction, κ differs dramatically from the popular Kramers constant friction predictions; this has important implications for the validity of transition state theory. (d) For solutionreactions heavily influenced by spatial diffusion, we show that the SSP isolates short range reaction dynamics of interest and includes important barrier region effects in structural isomerizations often missed in standard descriptions.

1,082 citations

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TL;DR: A theory for surface enhanced Raman scattering (SERS) is developed in this paper, where the surface is modeled as a hemispheroid protruding from a conducting plane.

Abstract: A theory for surface enhanced Raman scattering (SERS) is developed Effects due to realistic surface geometry and dielectric properties are included Three sources of enhanced Raman scattering are noted: the image dipole enhancement effect, the increase of local field (’’lightning rod’’ effect), and the resonant excitation of surface plasmons The surface is modeled as a hemispheroid protruding from a conducting plane, although other models are considered The spherical limit is discussed in some detail and molecular orientation effects are considered Cross sections for Mie, Rayleigh, and Raman scattering are derived

940 citations

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TL;DR: In this paper, the distribution function of relaxation times underlying the nonexponential relaxation function of Williams and Watts is derived and compared with the analogous Cole-Davidson distribution function, and several useful relations between relaxation and distribution functions are summarized or derived, and the limitations of deriving distribution functions from relaxation functions are discussed.

Abstract: The distribution function of relaxation times underlying the nonexponential relaxation function of Williams and Watts is derived and compared with the analogous Cole–Davidson distribution function. In order to make the comparison between the two distribution functions, a simple empirical relationship between the Cole–Davidson and Williams–Watts parameters was determined which may be used to compare data analyzed using the two fitting functions. Although the relaxation functions are similar to each other, the distribution functions are quite dissimilar. The Cole–Davidson distribution shows a sharp long time cutoff, while the Williams–Watts distribution decays approximately exponentially at long times. Finally, several useful relations between relaxation and distribution functions are summarized or derived, and the limitations of deriving distribution functions from relaxation functions are discussed.

888 citations

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TL;DR: In this paper, a simple model based on connectivity concepts from correlated site percolation theory was proposed to examine the physical implications of the continuous hydrogen-bonded network formed by water molecules.

Abstract: The unusual low‐temperature behavior of liquid water is interpreted using a simple model based upon connectivity concepts from correlated‐site percolation theory. Emphasis is placed on examining the physical implications of the continuous hydrogen‐bonded network (or ’’gel’’) formed by water molecules. Each water molecule A is assigned to one of five species based on the number of ’’intact bonds’’ (the number of other molecules whose interaction energy with A is stronger than some cutoff VHB). It is demonstrated that in the present model the spatial positions of the various species are not randomly distributed but rather are correlated. In particular, it is seen that the infinite hydrogen‐bonded network contains tiny ’’patches’’ of four‐bonded molecules. Well‐defined predictions based upon the putative presence of these tiny patches are developed. In particular, we predict the detailed dependence upon (a) temperature, (b) dilution with the isotope D2O, (c) hydrostatic pressure greater than atmospheric, and...

706 citations

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TL;DR: In this article, an inhomogeneous differential equation is derived which yields τ by simple quadrature without taking recourse to detailed cumbersome time-dependent solutions of the original Smoluchowski equation.

Abstract: Association reactions involving diffusion in one, two, and three‐dimensional finite domains governed by Smoluchowski‐type equations (e.g., interchain reaction of macromolecules, ligand binding to receptors, repressor–operator association of DNA strand) are shown to be often well described by first‐order kinetics and characterized by an average reaction (passage) time τ. An inhomogeneous differential equation is derived which, for problems with high symmetry, yields τ by simple quadrature without taking recourse to detailed cumbersome time‐dependent solutions of the original Smoluchowski equation. The cases of diffusion and nondiffusion controlled processes are included in the treatment. For reaction processes involving free diffusion and intramolecular chain motion, the validity of the passage time approximation is analyzed.

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TL;DR: In this paper, qualitative features of the concentration fluctuations in binary polymer melts A+B, A and B being long, flexible chains, with a Flory interaction parameter χ which can be positive (favoring segregation), or negative.

Abstract: We discuss here some qualitative features of the concentration fluctuations in binary polymer melts A+B, A and B being long, flexible chains, with a Flory interaction parameter χ which can be positive (favoring segregation), or negative. In the one phase domain, the fluctuations of long wavelength (2π/q) are expected to relax by a reptation process. At shorter wavelengths (qR0≳1, where R0 is the size of one chain) equilibration takes place by local adjustment of each chain inside a fixed ’’tube’’: the predicted relaxation rates τq−1 are proportional to q6 for χ?0. (For a negative χ, opposing segregation, one expects τq−1∼q4). In the two phase domain, where the trend towards segregation is strong (χN≫1, N being the number of monomers per chain), one should observe a very anomalous type of spinodal decomposition: in the early stages, the growing fluctuations have a wavelength comparable to the thickness of the interfacial region, and small compared with R0: the growth is realized through local adjustment. D...

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TL;DR: In this paper, the effects of large amplitude vibrational motion have been estimated and the equilibrium geometry should lie within the above limits with χa and φd equal to zero.

Abstract: Radio frequency and microwave spectra for various isotopically substituted water dimers have been studied by molecular beam electric resonance spectroscopy. Resolved radio frequency hyperfine transitions have provided information about the tunneling–rotational levels of water dimer. The microwave spectra have been analyzed with a rigid rotor model to give the following structural information: Roo=2.976 A (+0.000, −0.030 A), ϑd=−51(10)°, ϑa=57(10)° and χa=6(20)°. The effects of large amplitude vibrational motion have been estimated and the equilibrium geometry should lie within the above limits. The experimental data is also consistent with χa and φd equal to zero for the equilibrium geometry. The water dimer structure, therefore, has a symmetry plane, a trans configuration, and a linear hydrogen bond within quoted error limits.

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TL;DR: In this paper, the authors studied the reaction of carbon monoxide catalyzed by Pt(111) using reactive molecular beam-surface scattering and showed that at low coverage, the reaction proceeds with an activation energy E*LH =24.1 kcal/mole and a pre-exponential υ4 =0.11 cm2 particles−1

Abstract: The oxidation of carbon monoxide catalyzed by Pt(111) was studied in ultrahigh vacuum using reactive molecular beam–surface scattering. Under all conditions studied, the reaction follows a Langmuir–Hinshelwood mechanism: the combination of a chemisorbed CO molecule and an oxygen adatom. When both reactants are at low coverage, the reaction proceeds with an activation energy E*LH =24.1 kcal/mole and a pre‐exponential υ4 =0.11 cm2 particles−1 sec−1. At very high oxygen coverage, E*LH decreases to about 11.7 kcal/mole and υ4 to about 2×10−6 cm2 particles−1 sec−1. This is largely attributed to the corresponding increase in the energy of the adsorbed reactants. When a CO molecule incident from the gas phase strikes the surface presaturated with oxygen, it enters a weakly held precursor state to chemisorption. Desorption from this state causes a decrease in chemisorption probability with temperature. Once chemisorbed, the CO molecule then has almost unit probability of reacting to produce CO2 below 540 K. The CO2 product angular distribution varies from cosγ to cos4γ depending sensitively upon the adsorbed reactant concentrations.

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TL;DR: In this paper, grand canonical Monte Carlo computations on the diffuse double layer in an ionic system next to a uniformly charged plane surface were performed for the 1:1 restricted primitive model at several concentrations and over a range of surface charge densities.

Abstract: This paper reports grand canonical Monte Carlo computations on the diffuse double layer in an ionic system next to a uniformly charged plane surface. The boundary conditions and the grand canonical techniques are discussed. Calculations were carried out for the 1:1 restricted primitive model at several concentrations and over a range of surface charge densities. The results are compared with the modified Gouy–Chapman theory, and some remarks are also possible with respect to the modified Poisson–Boltzmann and the hypernetted chain approaches. At high concentrations and surface charge densities the counterions are packed closely at the surface and begin to show a layered structure. This results in a large electrostatic potential drop, but only very slight charge oscillations are observed in the solution. None of the theories seems able to describe this behavior.

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TL;DR: In this paper, the authors use wave front solutions of reaction-diffusion equations with a realistic model of the reaction medium to account for most of the important features of target patterns in the Belousov-Zhabotinskii reaction.

Abstract: Periodic expanding target patterns of chemical activity are observed in thin layers of solution containing bromate, malonic acid and ferroin in dilute sulfuric acid. Commonly these patterns appear as thin blue (oxidized) rings propagating out from a central point into red (reduced) bulk medium. Recently, the opposite pattern has been observed: red waves of reduction propagating through an oxidized bulk medium. We discuss both of these patterns under the assumption that there is a heterogeneity at the center of the pattern—most likely a dust particle or a scratch on the glass—which changes the kinetics locally from a stable excitable steady state to a stable periodic oscillatory state. The temporal oscillation at the origin triggers waves of chemical activity which propagate radially into the excitable medium. Our approach is to combine recent advances in the mathematical description of traveling wave front solutions of reaction–diffusion equations with a realistic model of the kinetics of the reaction medium. The model we use, the Oregonator, is based on known features of the reaction mechanism, gives an acceptable qualitative and semiquantitative account of the reaction dynamics, and yet is simple enough to yield to analytic techniques developed primarily for scalar reaction–diffusion equations. With this approach we can account in some detail for most of the important features of target patterns in the Belousov–Zhabotinskii reaction. In particular, the distinction between trigger waves and phase waves is clarified by our analysis, and the novel properties of reducing waves in an oxidized medium appear as natural consequences of our model.

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TL;DR: In this paper, a polarization propagator approach was proposed to yield excitation energies, transition moments, and dynamic polarizabilities which are consistent through second order in the electronic repulsion.

Abstract: We have formulated a polarization propagator approach which yields excitation energies, transition moments, and dynamic polarizabilities which are consistent through second order in the electronic repulsion. Certain terms are proven to be missing in our previous second order calculations of transition moments and dynamic polarizabilities and in the equation‐of‐motion calculations of the same quantities. Numerical calculations on carbon monoxide are performed. The calculations show that the major difference between the polarizability (and some transition moments) in the RPA and in the second order polarization propagator approximation is due to these terms. The total effect of all correction terms has been to improve considerably the agreement between theoretical and experimental estimates of the excitation properties for carbon monoxide.

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TL;DR: Tirado et al. as mentioned in this paper extended the formalism for the calculation of translational friction coefficients of symmetric top macromolecules and derived analytical solutions that reduce to those obtained by other authors when the unmodified interaction tensor is used.

Abstract: The formalism for the calculation of translational friction coefficients of symmetric top macromolecules presented in a previous paper [M. M. Tirado and J. Garcia de la Torre, J. Chem. Phys. 71, 2585 (1979)] is here extended to the evaluation of rotational friction and diffusion coefficients. We show how the introduction of symmetry considerations leads to a great reduction of the computational requirements needed to solve the hydrodynamic interaction equations. We also obtain the translation–rotation coupling tensor from which the center of hydrodynamic stress can be obtained. For a rigid ring we have derived analytical solutions that reduce to those obtained by other authors when the unmodified interaction tensor is used. The general formalism is finally applied to the calculation of the rotational diffusion coefficients of circular cylinders modeled as stacks of rings and extrapolated to zero bead size. The resulting values are critically compared with those from earlier studies.

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TL;DR: In this article, a three dimensional generalized Langevin formalism is presented and applied to Ar and Xe interactions with Pt (111), and approximate parameters for the random force and friction terms are proposed which permit realistic description of the motion and response of the surface atoms, including proper correlations among neighboring atoms.

Abstract: A three dimensional generalized Langevin formalism is presented and applied to Ar and Xe interactions with Pt (111). Approximations for the random force and friction terms are proposed which permit realistic description of the motion and response of the surface atoms, including proper correlations among neighboring atoms. A ’’ghost atom’’ technique is developed which provides convenient numerical solution of the generalized Langevin equations in such a way that the fluctuation–dissipation theorem relating the random force and friction is satisfied rigorously. A simple prescription for determining parameters in the random force and friction is outlined. The prescription is applied to a four‐atom active zone to obtain explicit relationships for all parameters, depending only on the bulk and surface Debye frequencies, for fcc (100), (110), and (111), and bcc (100) and (110) surfaces. Calculations of energy accommodation, sticking probabilities, and thermal desorption rates are reported for Ar and Xe on Pt(111). The sensitivity of these properties on the parameters of the random force and friction, i.e., on the phonon spectrum, is examined. The dependence is found to be sufficiently weak to demonstrate convincingly that the generalized Langevin approach with relatively simple parameterization is capable of describing gas–surface dynamics with high accuracy.

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TL;DR: In this article, a simple treatment of dipolar contribution to nuclear magnetic relaxation is developed for molecules in which conformational fluctuations modulate the relevant internuclear distances, and approximate results for cross-correlation spectral densities are obtained for complex spin systems, e.g., An1Mn2Xn3....

Abstract: A simple treatment of the dipolar contribution to nuclear magnetic relaxation is developed for molecules in which conformational fluctuations modulate the relevant internuclear distances. Expressions are given for AX system spectral densities using a general model in which conformational fluctuations occur as random jumps among discrete conformations, while the molecule as a whole undergoes rotational diffusion as either a spherical or a symmetric top. Approximations valid for proton spin systems are given for cases in which the jumping rates are either fast or slow compared to rotational diffusion; the results are independent of the jumping rates. Similar results are obtained for cross‐correlation spectral densities. For complex spin systems, e.g., An1Mn2Xn3..., the cross‐relaxation constants σij which couple pairs of magnetizations, depend only upon autocorrelation, spectral densities and are thus easily obtained from the AX system results. Measurement of σij by time resolved Overhauser effect experimen...

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TL;DR: In this article, a quadratically convergent MC-SCF procedure is described, which is based on the direct minimization of the energy, and the convergence radius is much improved by taking into account in the energy expansion those parts of third and higher order terms which account exactly for the orthonormality constraints imposed on the orbitals.

Abstract: A quadratically convergent MC–SCF procedure is described which is based on the direct minimization of the energy. In comparison to the Newton–Raphson technique, which has previously been applied by several authors for orbital optimization, the convergence radius is much improved by taking into account in the energy expansion those parts of third and higher order terms which account exactly for the orthonormality constraints imposed on the orbitals. The nonlinear equations which define the improved orbitals are solved iteratively by a simple adaption of the Gauss–Seidel method. The coefficients of the configuration expansion can be optimized simultaneously with the orbitals, a necessary requirement for over‐all quadratic convergence. The removal of redundant variables as well as useful approximations for the optimization of core orbitals are discussed. The convergence of the method is demonstrated to be much superior to classical Fock operator techniques and MC–SCF methods which are based on the generalized Brillouin theorem. The formalism is carried down to matrix operations and shows a simple structure.

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TL;DR: In this paper, the coupling coefficients appearing in the direct CI formalism are factorized into a complicated internal part and a simple external part, which is then used for the unitary group formulation of the correlation problem.

Abstract: The direct CI method is generalized to the case of all single and double replacements from an arbitrary set of reference configurations. This is a continuation of the work and ideas presented in an earlier paper on first order wave functions. The analysis is done using the unitary group formulation of the correlation problem, and the resulting method is a combination of the direct CI method and the unitary group approach as formulated particularly by Paldus and Shavitt. The main idea in the present work is the factorization of the coupling coefficients appearing in the direct CI formalism, into a complicated internal part and a simple external part. The general philosophy is like in all direct CI methods to allow long CI expansions by avoiding the storage and retrieval of a large formula tape. The longest CI expansion treated in this paper is an application on the system CH2(3B1)+H2→CH3+H with five reference states, resulting in 16 096 configurations. The barrier height for the reaction is calculated to b...

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TL;DR: In this paper, a short-range repulsive interaction model was proposed to explain the mutual configuration of the adsorbed molecules, which is supported by the observation that the isosteric heat of adsorption (Ead=38.5 kcal/mole) is constant up to a coverage of Θ?0.5.

Abstract: Adsorption of CO on a Pd(100) surface was studied in detail mainly by LEED, UPS, work function and thermal desorption measurements. Analysis of the ordered c(2√2×√2) R 45° structure occurring at Θ=0.5 revealed that in this phase each CO molecule is bridge bonded to 2 Pd atoms with Pd–C distances of 1.93±0.07 A and a C–O bond length of 1.15±0.1 A, the molecular axis being oriented normal to the surface. The mutual configuration of the adsorbed molecules is explained in terms of a short‐range repulsive interaction model, which is supported by the observation that the isosteric heat of adsorption (Ead=38.5 kcal/mole) is constant up to a coverage of Θ?0.45. The photoelectron spectra exhibit two maxima at 7.9 (5σ+1π level) and 10.8 eV (4σ level) below the Fermi level which are in agreement with the observations with other Pd planes. This also holds for an electronic excitation associated with an energy of 13.5 eV as observed by electron energy loss spectroscopy. The variation of the sticking coefficient with coverage is described in terms of a second‐order precursor state model with repulsive interactions. The pre‐exponential factor for desorption (3×1016 sec−1) varies only little with coverage. The dipole moment of the adsorbate remains constant up to Θ?0.35 (0.17 D) where the overlayer starts to order, and exhibits an appreciable higher value near Θ=0.5. The maximum work function increase is Δφmax=0.93 V at Θ=0.5. The differential entropy of the adsorbed layer around 450 K was derived from the experimental adsorption isotherms. Up to Θ=0.35 the data fall well between the limits of two theoretical models for localised and delocalised adsorption of noninteracting particles. Deviations at higher coverages reflect again the onset of ordering. The energetic and work function data are in some variance to results reported earlier which is ascribed to the fact that these quantities may be sensitively influenced by spurious amounts of carbon impurities on the surface.

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TL;DR: In this article, the Jeener-Broekaert pulse sequence was used to detect deuteron line shapes, from which the orientational distribution of partially ordered solids or solid polymers may be determined.

Abstract: Deuteron spin alignment offers a new possibility to investigate extremely slow rotational motions in solids and solid polymers. A convenient theoretical description of the creation and detection of spin alignment by application of the Jeener–Broekaert pulse sequence is given for both static and slowly time dependent quadrupole coupling, as well as for spin–lattice relaxation of spin alignment. It is shown that the NMR signal following spin alignment yields a correlation function of the time dependent quadrupole coupling. This correlation function is evaluated explicitly for a deuteron on the corner of a regular tetrahedron undergoing tetrahedral jumps. Various applications of deuteron spin alignment are demonstrated experimentally, e.g., its use to obtain undistorted deuteron line shapes, from which the orientational distribution of partially ordered solids or solid polymers may be determined. In solid polyethylene it is shown that not only the deuterons in the crystalline regions but those in the mobile ...

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TL;DR: In this article, the structural details of doped polyacetylene (a highly conducting organic polymer) were studied using optical absorption, Raman, and infrared spectra of polyacetylenes.

Abstract: In order to elucidate the structural details of doped polyacetylene (a highly conducting organic polymer), the optical absorption, Raman, and infrared spectra of not only trans‐(CH)x doped with iodine, AsF5, and SO3 but also β‐carotene doped with iodine and SO3 were studied. The infrared spectra of two kinds of isotopically substituted polyacetylenes (CD)x and (13CH)x doped with iodine were also observed. Analysis of the experimental results shows that upon doping each of the four vibrational branches (ν1–ν4) in the 1600–900 cm−1 region of a polyene chain splits into two groups, namely, the higher frequency group and the lower frequency one. The former group consists of the ’’gerade’’ vibrations of polyene parts which are not directly attacked by dopants but are perturbed along the chain, whereas the latter is made up of the ’’ungerade’’ vibrations of the positively charged polyene part with the doped site at its center. The Raman bands in the higher‐frequency group of ν1 (mainly the C=C stretching mode) ...

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TL;DR: In this paper, the grand canonical ensemble Monte Carlo method is used to calculate the density profile of a simple dense liquid, under conditions close to the vapor line, between two solid bodies and also the solvation force between the solids due to the simple fluid.

Abstract: The grand canonical ensemble Monte Carlo method is used to calculate the density profile of a simple dense liquid, under conditions close to the vapor line, between two solid bodies and also the solvation force between the solids due to the simple fluid. The force is large compared with the van der Waals force at moderate surface separations, h, but is an oscillatory function of h. At small values of h the solvation force is strongly repulsive.

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TL;DR: In this paper, the theory of energy shifts in mirror image molecules arising from parity nonconserving weak neutral currents is developed, and its connection with the theories of optical activity is discussed.

Abstract: The theory of energy shifts in mirror‐image molecules arising from parity nonconserving weak neutral currents is developed. Its connection with the theory of optical activity is discussed. In order to demonstrate the existence of the energy shift, which produces an energy difference between an optically active molecule and its mirror image, an exact calculation is performed for a simple one‐electron model (the Condon model). Then approximate LCAO‐MO calculations are performed on two specific molecules, twisted ethylene and A‐nor‐2‐thiacholestane, in order to obtain more reliable order‐of‐magnitude estimates of the energy shifts than available previously. According to our calculations, the former molecule has an energy shift two orders of magnitude larger than the latter, but both molecules have energy shifts which are appreciably smaller than the previous estimates.

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TL;DR: In this article, the results of an experimental study of electrical conductivity and thermopower in doped polyacetylene are reported, where measurements on both as‐grown and partially oriented films doped with iodine and AsF5; [CH(AsF5)y]x and [CH[I3]x, where y covers the full doping range.

Abstract: The results of an experimental study of electrical conductivity and thermopower in doped polyacetylene are reported. Included are measurements on both as‐grown and partially oriented films doped with iodine and AsF5; [CH(AsF5)y]xand [CH(I3)y]x, where y covers the full doping range. The data indicate three important concentration regimes; the dilute limit (y<0.001), the transitional region (0.001

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TL;DR: In this paper, the authors reported the results of multiple scattered wave SCF X-alpha calculations of the one-electron cross section for K-shell photoabsorption in the molecular complexes MoO4−−, CrO4+−, and MoS4−+−.

Abstract: We report the results of multiple scattered wave SCF X‐alpha calculations of the one‐electron cross section for K‐shell photoabsorption in the molecular complexes MoO4−−, CrO4−−, and MoS4−−. We show that the method can successfully account for energy separations and relative cross sections of spectral features both below and above the K‐shell ionization threshold. Furthermore, we show: (a) that the first fairly intense peak on the low energy side of the rising edge for molybdate and chromate is due to a dipole allowed transition to a bound antibonding state of mainly nd character on the metal ion; this transition is possible because of the mixing with the ligand p orbitals having the proper T2 symmetry induced by the tetrahedral molecular potential; (b) the shoulder on the rising absorption edge can be explained by the beginning of the steplike continuum absorption when convolved with a Lorentzian function of frequency to imitate lifetime and monochromator broadening: (c) the main absorption peak is due t...