bluuebunny/crossref_metadata_2025 huggingface dataset:
Detailed balance in far-wing line shape theories: Comparisons between different formalisms
Authors: Ma Q. , Tipping R. H. , Hartmann J.-M. , Boulet C.
Published: July 2002

Comparisons are made between different methods of introducing the principle of detailed balance in far-wing line shape theories. In particular, it is shown that by symmetrizing the operators in the quasistatic formulation of Ma and Tipping [J. Chem. Phys. 95, 6290 (1991)], one can obtain the same results for the symmetrized matrix elements of the relaxation operator and their frequency detuning that were introduced in an ad hoc way in the resonant quasistatic formulations of Boulet and co-workers [J. Chem. Phys. 91, 2163 (1989); 94, 6406 (1991)].
Helmholtz free energy of a cluster on the coherent substrate: Monte Carlo calculations
Authors: Zapadinsky Evgeni L. , Kulmala Markku
Published: July 2002

Monte Carlo simulations of clusters on underlying substrate have been performed. A cluster free energy has been calculated for different substrate lattice parameters. Computing efforts have been focused on the case when a substrate lattice was approximately the same as a bulk crystal lattice consisting of the cluster molecules. The present calculations qualitatively confirm the dependence of the cluster free energy on a misfit between the lattices found in previous studies [D. Turnbull and B. Vonnegut, Ind. Eng. Chem. 44, 1292 (1952) and N. Cabrera, Mem. Sci. Rev. Metall. 62, 205 (1965)]. The effect of the misfit turns out to grow when the number of molecules in the cluster increases. The aforementioned studies of Turnbull and Vonnegut, and Cabrera predicted less strong dependence of the effect of the misfit on the number of molecules in the cluster.
Coherence transfer in three-level systems: Controlled violation of adiabaticity and antiparallel double resonant irradiation
Authors: Ermakov Vladimir L. , Bodenhausen Geoffrey
Published: July 2002

It is shown by theory and experiment how coherent superpositions of quantum states in three-level systems can be manipulated by irradiating two connected transitions with two resonant fields with suitably shaped time-dependent amplitudes and phases. Three variants are discussed in detail; (i) adiabatic coherence transfer (ACT) between two transitions, which may be either allowed or forbidden; (ii) nonadiabatic transfer of coherence to a nonirradiated transition by controlled violation of adiabaticity (CVA); (iii) coherence transfer to a nonirradiated transition by antiparallel double resonant irradiation (APDRI). A geometrical representation of these experiments gives a clear physical picture of the phenomena and provides a tool for the development of new methods. The principles are illustrated experimentally by applications to magnetic resonance of deuterium (I=1) in anisotropic phase at high magnetic field, but could also be applied to three level-systems in nuclear quadrupole resonance, optics, and other areas of spectroscopy.
Transmission of low energy (<10 eV) 16O+ ions through condensed ammonia and water overlayers
Authors: Akbulut Mustafa , Sack Norbert J. , Madey Theodore E.
Published: July 2002

We have studied the transmission of low energy (<10 eV) 16O+ ions through ultrathin films of condensed molecular solids, NH3 and H218O, in order to address the fundamental scattering processes that occur in the desorption of ions from below the surface of solids. 16O+ ions with a peak energy of ∼7 eV and a narrow angular distribution [full-width at half-maximum (FWHM) ∼15°] are generated by means of electron stimulated desorption (ESD) from an 16O oxidized W(100) surface and their yield, energy and angular distribution are measured with a digital ESDIAD (ESD ion angular distribution) detector. Ultrathin NH3 and H218O films of known thickness are condensed on the oxidized surface at 25 K and changes in the ion yield, energy and angular distribution are observed as a function of coverage. We find that adsorption of only 0.5 monolayer of H218O is enough to suppress the 16O+ ion emission by a factor of 100, while three monolayers of NH3 are necessary for equivalent suppression of the 16O+ ion emission. The angular distribution of the ions increases slightly with increasing overlayer coverage. We also find that a small percentage of H218O dissociates upon adsorption. We suggest that one electron charge transfer between 16O+ and H218O, and between 16O+ and the dissociation product OH are the main reasons for the strong attenuation of 16O+ ions by only a fraction of a monolayer of H218O. Charge transfer is also believed to be the main process that causes suppression of 16O+ ions by ultrathin NH3 films. Other elastic and inelastic processes are not believed to contribute significantly to 16O+ attenuation in NH3 or H218O films.
Vibrational properties of small two-dimensional classical crystals
Authors: Hoover William G. , Kum Oyeon
Published: July 2002

Recent computer simulations have stressed the dependence of transport properties on boundary conditions in two dimensions, where fluctuations and boundary conditions are equally important effects of order N1/2. Elastically isotropic harmonic crystals provide a test case in which these two effects can be studied precisely without sacrificing realism. We investigate the boundary dependence of spatial fluctuations in two-dimensional crystals. Our results confirm the expected boundary independence of the extensive vibrational entropy. We find also that clamped crystal boundaries significantly alter the rate of divergence of the root-mean-square (rms) displacement with crystal size, but do not alter the [logarithmic] functional form, which is known to dominate vibrational fluctuations in periodic two-dimensional crystals.
Simulated annealing using coarse grained classical dynamics: Smoluchowski dynamics in the Gaussian density approximation
Authors: Straub John E. , Ma Jianpeng , Amara Patricia
Published: July 2002

A dynamical annealing algorithm for global optimization based on approximate solution of the Smoluchowski equation is presented. The equations of motion in the Gaussian density approximation are interpreted as a steepest descent quench on a time dependent effective potential energy surface. A relation between the convexity condition for the effective potential surface and the size of thermal fluctuations provides a definition of the critical temperature above which the distribution is delocalized and the effective potential is smooth and convex during an annealing run. This critical temperature may be significantly less than the temperature characteristic of escape from a local energy minimum.
Theory of time-dependent nucleation and growth during a rapid quench
Authors: Shneidman Vitaly A.
Published: July 2002

Phase transformation via the nucleation and growth mechanism during a rapid cooling (quench) of a glass-forming liquid or melt is considered. Traditional approaches here are based on the quasi-steady-state (QSS) approximation for nucleation and the assumption of a size-independent growth. However, the QSS approach becomes invalid if the dimensionless rate of the barrier change, n=−τ∂(W*/kT)/∂t (τ is the inner time scale of the nucleation process) is not vanishingly small. For such ‘‘strongly time-dependent’’ situations an asymptotic (singular perturbation) technique of matching the time- and size-dependent nucleation and growth solutions is elaborated, and an explicit expression to describe the distribution function of large particles is derived. Formally, the results can be reproduced by the QSS approximation with the steady-state nucleation rate multiplied by an n-dependent factor. Analytical treatment is tested against numerically exact solutions of the nucleation (Becker–Döring) and growth equations.
Crystalline structures of pristine and hydrated mercaptohexanol self-assembled monolayers on Au(111)
Authors: Poirier G. E. , Pylant E. D. , White J. M.
Published: July 2002

The crystalline structure of hydroxy-functionalized hexanethiol self-assembled monolayers on Au(111) were characterized using gas-phase transport of molecular precursors and an ultrahigh vacuum scanning tunneling microscope. In the pristine state the monolayer exhibits a commensurate lattice with an oblique primitive unit-cell of dimensions a=3, b=√13, α=a tan(2√3); a structure that is fundamentally different than the hexagonal lattice observed for methyl-terminated monolayers. Hydration of the monolayer results in conversion to a polymorphic phase. These results demonstrate the importance of end-group chemical bonding in the molecular packing of this widely studied class of materials.
Hyperfine selectivity using multiquantum electron–nuclear–electron triple resonance
Authors: Christidis T. C. , Mchaourab Hassane S. , Hyde James S.
Published: July 2002

Hyperfine selectivity is demonstrated in a continuous wave electron–nuclear double resonance (ENDOR) experiment. A multiquantum electron–electron double resonance (ELDOR) signal is monitored as a function of the nuclear radio frequency. The signs and relative intensities of the ENDOR lines permit separating the case where both ELDOR and ENDOR frequencies match hyperfine couplings from the cases where this condition is not satisfied.
Prediction of the temperature dependence of the limiting diffusion coefficients of five helium–fluoromethane systems from diffusion coefficients at 300 K and limiting thermal diffusion factors at the same temperature and zero pressure
Authors: Dunlop Peter J. , Bignell C. M.
Published: July 2002

Thermal diffusion factors αT are reported at 300 K for five binary systems consisting of helium and a fluoromethane. The data are extrapolated to zero pressure and used to predict the temperature dependence of the binary diffusion coefficients of these systems.
Moderately dense gas quantum kinetic theory: Transport coefficient expressions
Authors: Snider R. F. , Wei G. W. , Muga J. G.
Published: July 2002

Expressions for the transport coefficients of a moderately dense gas are obtained, based on a recently derived density corrected quantum Boltzmann equation. Linearization of the equations determining the pair correlation and the ‘‘free’’ singlet density operators about local equilibrium is discussed first. The rate of change of the pair correlations is treated as dynamic effects for pairs of particles relaxing to local equilibrium via a relaxation time model arising from interactions with ‘‘third particles.’’ In contrast, the singlet density operator satisfies a Boltzmann equation with binary collisions. Spatially inhomogeneous corrections to the collision superoperator are included. Contributions to the transport coefficients arise from the perturbation from local equilibrium through fluxes associated with kinetic, collisional and, for the thermal conductivity, potential energy mechanisms. A comparison is made between the classical limit of the transport coefficient expressions obtained here and the classical expressions previously derived from the Boltzmann equation with the nonlocal collision corrections of Green and Bogoliubov.
Interaction between macroparticles in a simple model system of a nonpolar liquid containing trace amounts of water
Authors: Kinoshita Masahiro , Iba Shin-ya , Kuwamoto Ken , Harada Makoto
Published: July 2002

We report results of numerical analyses on the macroparticle interactions immersed in a simple model system of nonpolar liquid containing trace amounts of water. The singlet Ornstein–Zernike approach with the reference hypernetted-chain closures is employed. Particles of component 1 (water) are characterized by strong attractive interaction among them, those of component 2 (nonpolar liquid) are hard spheres, and particles of different components interact through hard-sphere potential. The mole fraction of component 1 x1 is very small. Beyond x1=x1P, the mixture cannot exist, even in the metastable state with a single phase. Some affinity is considered only between the macroparticle surface and component 1. When the affinity ξ (negative ξ implies repulsion) is increased with fixing x1 (at a value significantly smaller than x1P) and the macroparticle diameter dM, the macroparticle interaction φMM shifts to the lower (more attractive) side and eventually becomes extremely long-ranged and divergent. For larger x1, the divergence occurs at lower ξ. Whenever φMM becomes divergent, the reduced density profile of component 1 near the surface also becomes extremely long-ranged and divergent. The effects of dM on φMM is also analyzed. At the stability limit (x1→x1P), the divergences occur irrespective of ξ and dM, which is consistent with the recent prediction [Attard et al., Phys. Rev. A 45, 7621 (1992)].
Collisional reactions of Nan+ (n=3–9) with N2O
Authors: Tanaka Hideki , Mizuno Tomoyuki , Ishizaki Fumihiko , Nonose Shinji , Kondow Tamotsu
Published: July 2002

A collisional reaction of a sodium cluster ion, Nan+(n=3–9), with a nitrous oxide molecule, N2O, was investigated by using a tandem mass-spectrometer equipped with four octopole ion guides. Two types of ions, NakO+ and Nap+ (p<n), were produced by the reaction; NakO+ and Nap+ result from oxidation and direct collisional dissociation of the parent cluster ion, Nan+, respectively. The absolute total cross section and partial cross sections for the NakO+ (oxidation) and Nap+ (direct dissociation) production were measured as a function of the collision energy of a given parent cluster ion, Nan+, in the energy range up to 5 eV (center-of-mass frame). The cross sections and their collision-energy dependence show that the oxidation proceeds when electron harpooning from Nan+ to N2O occurs and otherwise the direct collisional dissociation proceeds.
The unrestricted Hartree-Fock self consistent field calculation for spin density wave state in metallic carbon nanotube
Authors: Kobayashi Katsushi
Published: July 2002

The possibility of a spin density wave (SDW) state in a metallic carbon nanotube (CN) and its electronic properties are investigated within the Hartree-Fock self consistent field (SCF) energy-band calculation. Two kinds of spatial SDW states are assumed in this study. Each assumed SDW on the wave function is constructed with the degenerate π orbital in the metallic CN system. The results calculated for the one SDW model of CN always have a relative stability (∼ 0.1 eV/cell) in SCF total energy compared with the original model in which no SDW is assumed. All the results calculated for another SDW model are completely equal to the original one. Moreover, in the energy dispersion of the former stable SDW model, the degenerate π level found in the original model disappears and the band gap (3-5 eV) occurs around at the Fermi level. The energetic stability and the band gap are also found in the π-electron band calculation within the Hubbard Hamiltonian.
State-to-state scattering of metastable CO molecules from a LiF (100) surface
Authors: Jongma Rienk T. , Berden Giel , Rasing Theo , Zacharias Helmut , Meijer Gerard
Published: July 2002

Scattering of electronically excited, state-selected metastable CO(aΠ3) molecules from a cleaved LiF(100) surface is studied experimentally. Internal state distributions, fluorescence profiles, time-of-flight (TOF) profiles and angular distributions of the surviving metastable CO molecules are measured. Relative and absolute survival probabilities are determined for various impact velocities. The dependence of translation and rotational temperature on the velocity of the incoming beam unambiguously indicates a direct inelastic scattering process, even though the angular distributions are broad, both in plane and out of plane. The internal state distribution after scattering shows an overpopulation of the initially prepared Ω=1-component relative to the other spin components.
State-specific reaction and product energy disposal of electronically excited potassium with hydrogen molecule
Authors: Liu Dean-Kuo , Lin King-Chuen
Published: July 2002

Using a pump–probe technique, we have systematically studied the state-selected effect on the K–H2 reaction, showing that the reactivity follows the trend of D<P<S. As long as the system is energetically allowed for reaction, the potential energy is not the key parameter, but the atomic orbital symmetry determines such a state selectivity. The observation of KH(v=0–3) rotational population in the reaction of K(6s,7s) corresponds to a statistical thermal distribution at 610±20 K. In contrast, the vibration is highly excited, yielding a Boltzmann vibrational temperature of 2946±110 and 3150±200 K. These results provide evidence that the attacking K atom approaches along a collinear geometry, and KH is produced via an ion-pair K+H2− intermediate as a likely pathway. The fraction of product energy partitioning yields 70%, 26%, and 4% for translation, vibration, and rotation. The individual energy disposal into vibration increases with the excitation energy of K. The fact indicates that the electron jumping distance elongates along the order of 5P<6S<6P<7S<7P, consistent with the prediction by the harpoon mechanism. Most available energy dissipation into translation is caused by a strong instability of the H2− bond. The repulsive energy release from the H2− bond rupture is seriously affected by the attraction between K+ and H−. Therefore, the direct interaction with product repulsion (DIPR) model may not be valid to describe the current system. As “mixed energy release” concept is considered instead, a disposal comparison of available energy among the reactions of K–Br2, K–H2, and Cs–H2 may be rationalized.
Chromophore dependence of intramolecular vibrational relaxation: Si–H stretch second overtone versus C–H stretch first overtone in methylsilane
Authors: Dolce J. W. , Callegari A. , Meyer B. , Lehmann K. K. , Scoles G.
Published: July 2002

The intramolecular vibrational relaxation (IVR) of an excited Si–H stretch (second overtone) and C–H stretch (first overtone) in methylsilane has been examined by eigenstate resolved infrared spectroscopy. The experiment probes a molecular beam produced in a supersonic expansion, excited by a laser in a power buildup cavity, and detected by a liquid helium cooled silicon bolometer. The Si–H stretch [local mode (3,0,0), both A and E combinations] is compared with the nearly isoenergetic C–H stretch [predominantly the 2ν70 band]. With the calculated density of states almost unchanged, the two modes exhibit very different IVR behavior, which is quantified in terms of the lifetime of the bright states and the coupling between the bright states and the dark states.
Measurements of structural and quadrupole coupling parameters for bromoferrocene using microwave spectroscopy
Authors: Drouin Brian J. , Lavaty T. Greg , Cassak Paul A. , Kukolich Stephen G.
Published: July 2002

Rotational spectra for two isotopomers of bromoferrocene were measured using pulsed-beam Fourier transform microwave spectroscopy. Transitions were observed for the 79Br and 81Br isotopomers in the 5–9 GHz range. Rotational constants and the quadrupole coupling tensors were obtained from the data. The rotational constants and quadrupole coupling parameters for 79Br are A=1272.110(1), B=516.1125(2), C=441.3775(2), eQqaa=267.16(3), eQqab=−409.81(4), and eQqbb=21.49(4), and those for 81Br are A=1271.045(4), B=510.0079(2), C=436.7687(2), eQqaa=225.40(6), eQqab=−341.62(4), and eQqbb=15.65(4). The measured rotational constants were used to determine the following structural parameters of bromoferrocene: r(Fe–(C5H5))=1.63(2), r(Fe–(C5H4Br))=1.67(3), r(C–Br)=1.875(11), and r(C–C)=1.433(1) Å. The values of the quadrupole coupling parameters in the principal quadrupole axis systems and the C–Br bond axis systems are compared with similarly derived parameters for chloroferrocene, chlorobenzene, and bromobenzene. Previous data for chloroferrocene has been reanalyzed to obtain refined quadrupole parameters.
Hartree-Fock energy-density functionals generated by local-scaling transformations: Applications to first-row atoms
Authors: López-Boada R. , Ludeña E. V. , Karasiev V. , Pino R.
Published: July 2002

We report energy calculations of selected first-row atoms using explicit approximate Hartree-Fock functionals generated in the context of the local-scaling version of density functional theory. We show that these approximate functionals yield highly accurate upper bounds to the Hartree-Fock energies of the atoms considered. The generation of molecular functionals in terms of local-scaling transformations centered at each nucleus is discussed.
Global energy dependence of N2O+(A 2Σ+) photoion alignment
Authors: Das Romith , Wu Chuanyong , Poliakoff E. D.
Published: July 2002

We present experimental results for the alignment of N2O+(A 2Σ+) photoions over an extended energy range (16.4⩽hνexc⩽240 eV). The polarization of the N2O+(A 2Σ+→X 2Π) fluorescence is used to interpret the oscillator strength distributions for normally unresolved degenerate ionization channels. The results clearly show the influence of a near-threshold 7σ→kσ shape resonance, and help to clarify the results of previous fluorescence and photoelectron studies. At high photon energies, the photoelectrons are not favored to exit via a particular channel, in contrast to recent results on N2 and CO, where photoelectrons are ejected preferentially via the kσ channel and the photoions retain significant alignment even at the highest measurable energies. These results demonstrate that even well above threshold the spectral dependence of the alignment (i.e., polarization) is very sensitive to the molecular environment for photoejection.
Coupled cluster calculations for HC9NH+, a cation of interest to astrochemistry
Authors: Heyl Ä. , Botschwina P. , Hirano T.
Published: July 2002

An accurate equilibrium geometry was obtained for the astrochemically important cation HC9NH+by means of coupled cluster calculations including connected triple substitutions [CCSD(I)] and empirical corrections. The corresponding equilibrium rotational constant is Be=286.2 Mhz. A large equilibrium dipole moment of μe=9.26 D is predicted, which should facilitate the detection of the cation by means of microwave spectroscopy and radio astronomy. Wave numbers for the harmonic stretching vibrations of HC9NH+ are reported.
New inter-Rydberg transitions of NO revealed by the laser induced amplified spontaneous emission
Authors: Ogi Yoshihiro , Sugita Akihiro , Suzuki Hidefumi , Tanaka Yoshihito , Tsukiyama Koichi
Published: July 2002

Amplified spontaneous emission (ASE) from single rotational levels of Rydberg states, 4pσM 2Σ+, 4pπK 2Π, 5sσS 2Σ+, 4dσO 2Σ+, 4dπO′ 2Π, 5pσR 2Σ+, and 5pπQ 2Π of NO molecules has been investigated through optical–optical double resonance excitation via the A 2Σ+ state. Several new inter-Rydberg transitions were identified in the midinfrared region. The rotational structure in dispersed ASE spectra was resolved completely, which provided detailed information on cascading radiative relaxation processes among Rydberg states.
Molecular integrals over real solid spherical Gaussian-type functions
Authors: Matsuoka Osamu
Published: July 2002

Compact formulas are derived of molecular energy integrals over real solid spherical Gaussian-type functions using the Talmi transformation. A new method for calculating the Talmi coefficients is presented, which does not require angular-momentum algebra of 3j and 9j symbols.
Anomalous low frequency dispersion and dielectric relaxation in the layered intercalated compounds Cd0.75PS3A0.5(H2O) [A=K, Cs]
Authors: Jeevanandam P. , Vasudevan S.
Published: July 2002

The dielectric response in the layered Cd0.75PS3A0.5(H2O) [A=K, Cs] in which hydrated alkali cations reside in the interlamellar space, have been investigated as a function of frequency and temperature. In these materials the layers are electrically insulating, the alkali ions immobile and the electrical response due to the intercalated water molecules. The dielectric behavior shows two phenomena, an anomalous dispersion of the complex dielectric susceptibility at low frequencies and a dielectric relaxation at higher frequencies. At low frequencies the complex dielectric permittivity of both compounds show a power law dispersion with a transition to a smaller exponent above a crossover frequency, ωc. It was found that although ωc shifts to higher frequency with increasing temperature the magnitude of the complex permittivity at the crossover frequency showed no variation. The loss peak showed a similar shift to higher frequencies with temperature. The dielectric relaxation showed increasing departure from an ideal Debye response with temperature. The results have been rationalized by considering the intercalated water molecules as forming a H-bonded network structure. The dielectric behavior is described in the context of a percolation structure for this network. The anomalous low frequency dispersion arises due to imperfect transport on this structure and the dielectric loss due to the fact that the water molecules possess a permanent dipole moment.
Dielectric relaxation in binary solutions: Theory and experimental results
Authors: Bertolini Davide , Cassettari Mario , Ferrari Carlo , Tombari Elpidio
Published: July 2002

In this paper we present a statistical model to describe the dielectric behavior of binary solutions. The formal development is based on the introduction of a few dynamical parameters describing the interactions occurring in the solution; these parameters enter in the rate equations for the dynamics of mixing. These equations, after suitable linearization, are used as the starting point to obtain the dipole correlation functions necessary to study the dielectric relaxation processes. The model is able to indicate the conditions which a mixture composed of two liquids with very different relaxation times must fulfill to produce a single relaxation time, as often experimentally observed. Some significant results reported in the literature are analyzed and explained and new experimental data are reported in order to test specific features of the model. All tests carried out so far on binary solutions give a successful reproduction of experimental results.
Theoretical study of the sum frequency generation in molecular adsorbate: NH3/MgO(100)
Authors: Pouthier V. , Ramseyer C. , Girardet C.
Published: July 2002

We present a theoretical study of the sum frequency generation (SFG) for the ammonia molecule adsorbed on the MgO(100) surface. This particular system could be a model for experimentalists in order to test this nonlinear technique, mainly for two reasons. First, the ammonia molecules can be considered in a first approximation as isolated on the surface due to repulsive lateral interactions. Second, the symmetry of ammonia and its particular equilibrium configuration on this surface allow us to separate the SFG response in a part which depends only on the non linear susceptibility of the molecules and an other part that characterizes the experimental setup. As a consequence, the bandshifts and widths of the SFG and infrared (IR) signals can be directly compared. Within the accuracy of the vibrational dependence of the molecular parameters, our calculations predict that the SFG signals connected to the symmetric vibrational modes should be more intense than the antisymmetric ones, in consistency with the IR and Raman spectroscopies and that the two symmetric modes should be observable while only the bending vibration has a significant intensity in IR. Finally, we discuss in terms of beam polarizations, the geometry of the experimental setup which optimizes the detected intensities.
A theory of the linear viscoelastic properties of dilute solutions of coiling polymers. II. A first-order mechanical thermodynamic property
Authors: Rouse Prince E.
Published: July 2002

The theory is corrected to include relaxation processes fundamentally different in character from the configurational diffusion considered before. These processes involve relatively persistent intramolecular “cryptocrystallites.” Viscous flow places stress on these clusters of van der Waals bonds, storing free energy. Dissipation of this energy during the ensuing drift toward equilibrium contributes to the viscous losses. These quasichemical, scalar processes and the vectorial process of configurational diffusion proceed independently of one another. In systems in which many “cryptocrystallites” tend to form, these clusters make a contribution to viscosity almost directly proportional to the concentration of the polymer. If formation of persistent clusters is less likely, the contribution of clusters to the viscosity will increase with increasing molecular weight, finally becoming proportional to polymer concentration. All processes contributing to viscosity and viscoelasticity of these solutions are treated as relaxation phenomena. The inherent incompatibility with this theory of steady-state hydrodynamic expressions such as Stokes’ law or the Oseen tensor is stressed.
Kinetics of irreversible adsorption of deformable proteins
Authors: Zhdanov V. P. , Kasemo B.
Published: July 2002

Employing the Monte Carlo technique, we study the kinetics of random sequential adsorption of proteins in the case when this process is complicated by denaturation of proteins. Adsorbed denatured proteins are considered to be deformable, i.e., their shape may relax during adsorption of newly arriving proteins or denaturation of other adsorbed proteins. Using realistic values of the model parameters, we show that this effect may influence the late stage of the protein adsorption kinetics.
Solubility of nonpolar solutes in water: Computer simulations using the CF1 central force model
Authors: Arthur Jonathan W. , Haymet A. D. J.
Published: July 2002

Nonpolar solutes in water are modeled by the CF1 central force model for the water-water interactions and a shifted-force Lennard-Jones potential function for the solute-water interactions. Thermodynamic integration is used to calculate the solvation free energy of solutes of various sizes. A systematic exploration of the effect of the size of the solute and the depth of the potential well is carried out. This allows an examination of the change in the solvation free energy as the solute size and potential well depth are independently varied. The solvation free energies of the noble gas series are also studied. The results compare favorably with experiment and previous studies, indicating the suitability of the CF1 model of water for use in free energy calculations. An information theory approximation is used to calculate the solvation free energy for hard spheres of various sizes from a simulation of pure CF1 water. The results of this approximation show trends similar to the results of our simulations using the modified shifted-force potentials.
Comment on “Morphology-dependent stimulated Raman scattering imaging” [J. Chem. Phys. 105, 7276 (1996)]
Authors: Campillo A. J. , Eversole J. D. , Lin H-B.
Published: July 2002

We comment on a recent paper by J.-X. Zhang, P. A. Moortgat, and P. M. Aker [J. Chem. Phys. 105, 7276 (1996)]. We disagree with their interpretation of droplet stimulated Raman scattering spectral data as well as claims that surface electrical charge greatly affects hydrogen bonding at micrometer depths into water droplets.
Zinc oxide and its anion: A negative ion photoelectron spectroscopic study
Authors: Fancher C. A. , de Clercq H. L. , Thomas O. C. , Robinson D. W. , Bowen K. H.
Published: July 2002

We have recorded, assigned, and analyzed the photoelectron spectrum of ZnO−. The adiabatic electron affinity (E.A.a) of ZnO and the vibrational frequencies of both ZnO and ZnO− were determined directly from the spectrum, with a Franck–Condon analysis of its vibrational profile providing additional refinements to these parameters along with structural information. As a result, we found that E.A.a(ZnO)=2.088±0.010 eV, ωe(ZnO)=805±40 cm−1, ωe(ZnO−)=625±40 cm−1, and that re(ZnO−)>re(ZnO) by 0.07 Å. Since our measured value of E.A.a(ZnO) is 0.63 eV larger than the literature value of E.A.(O), it was also evident, through a thermochemical cycle, that D0(ZnO−)>D0(ZnO) by 0.63 eV. This, together with the literature value of D0(ZnO), gives a value for D0(ZnO−) of 2.24 eV. Since the extra electron in ZnO− is expected to occupy an antibonding orbital, the combination of D0(ZnO−)>D0(ZnO), ωe(ZnO−)<ωe(ZnO), and re(ZnO−)>re(ZnO) was initially puzzling. An explanation was provided by the calculations of Bauschlicher and Partridge, which are presented in the accompanying paper. Their work showed that our experimental findings can be understood in terms of the a 3Π state of ZnO dissociating to its ground-state atoms, while the X 1Σ+ state of ZnO formally dissociates to a higher energy atomic asymptote.
Unambiguous formalism of molecular vibrations: Use of redundant coordinates and canonical matrices
Authors: Martı́nez Torres E. , López González J. J. , Fernández Gómez M.
Published: July 2002

This paper introduces a new approach to the problem of describing molecular vibrations in redundant valence coordinates. A consistent definition for canonical force field, which is different of that by Kuczera and Pupyshev et al., is outlined. This new definition is also generalized to other matrices like kinetic-energy matrices and transformation matrices between different sets of vibrational coordinates. The importance of such canonical matrices follows from the fact that they are uniquely determined and allow us to consider the redundant coordinates as though they were independent.
Time evolution of pendular states created by the interaction of molecular polarizability with a pulsed nonresonant laser field
Authors: Ortigoso Juan , Rodrı́guez Mirta , Gupta Manish , Friedrich Bretislav
Published: July 2002

Previous investigations have shown that the instantaneous eigenstates of a molecule interacting via its polarizability with a strong electric field of a nonresonant laser pulse are pendular hybrids of field-free rotational states, aligned along the field direction. However, nonadiabatic effects during the time evolution of the initial field-free rotational state could cause the molecule to end up in a state described by a linear combination of pendular states (a rotational wavepacket) whose alignment properties are not a priori known. We report a computational study of the time evolution of these states. We solve the reduced time-dependent Schrödinger equation for an effective Hamiltonian acting within the vibronic ground state. Our numerical results show that the time evolution and the achievement of adiabatic behavior depend critically on the detailed characteristics of the laser pulse and the rotational constant of the molecule.
Chain dynamics in the nematic melt of an aromatic liquid crystalline copolyester: A molecular dynamics simulation study
Authors: Bharadwaj Rishikesh , Boyd Richard H.
Published: July 2002

A molecular dynamics (MD) simulation study of chain dynamics and the relation to dipolar relaxation has been carried out on a 70/30 composition random copolymer of p-hydroxybenzoic acid and 2-hydroxy-6-naphthoic acid. The dynamics is analyzed in terms of the relatively flexible torsion at the ester oxygen-aromatic carbon bond. The effective torsional potential in the bulk that results from sampled torsional angle populations is found to differ from that of free chains in that the barriers are higher in bulk and the torsion connecting phenyl and naphthyl units has a higher barrier than that between pairs of phenyl units. Activation energies for conformational transitions are higher than those in the effective potentials. These effects indicate sensitivity to packing not found in simpler systems like polyethylene, and that frictional effects are operative. The distribution of transitions over individual bonds is found to be quite heterogeneous over the temperature range studied and is a signature for a vitrifying system. Conformational jumps were not found to be highly correlated, although some preference for next-neighbor events was indicated. Dipolar time autocorrelation functions were constructed separately for phenyl and naphthyl dipoles. The naphthyl units were found to relax more slowly than the phenyls. Comparison of MD relaxation times with experimental loss maxima indicates a degree of correspondence that lends credence to the assignment of the experimental β relaxation subglass process as associated with the naphthyl units and the γ subglass process with the phenyl units.
Photoelectron spectrum of PdO−
Authors: Klopcic Stephan A. , Moravec Vicki D. , Jarrold Caroline Chick
Published: July 2002

The photoelectron spectrum of PdO− is presented and discussed. The spectrum exhibits multiple, close-lying electronic transitions from what appears to be a single state of the anion. The electron affinity of PdO is determined to be 1.570±0.006 eV. No vibrational structure is observed in the spectrum, but a recurring 780±60 cm−1 spacing appears to be from spin-orbit splitting in the low-lying  3Π neutral state.
Electronic excitation and oscillator strength of ethyl iodide by VUV photoabsorption and electron energy loss spectroscopy
Authors: Giuliani A. , Motte-Tollet F. , Delwiche J. , Heinesch J. , Mason N. J. , Gingell J. M. , Walker I. C. , Jones N. C. , Hubin-Franskin M.-J.
Published: July 2002

A high resolution VUV photoabsorption spectrum of ethyl iodide has been recorded between 4 and 10.2 eV (310–120 nm) using synchrotron radiation. The spectrum consists of a broad structureless absorption band centered at 4.78 eV, followed by a region dominated by excitation of Rydberg states. A high resolution photoelectron spectrum (PES) of the lowest energy ionization band has been obtained and provides ionization energies necessary for identification of related Rydberg-excited states. Also, analysis of the vibrational fine structure in the PES has allowed identification of the normal vibrational modes excited and their wave numbers in the ion. These, in turn, have been used in the assignment of the lowest energy photoabsorption bands arising from electron excitation into the 6s Rydberg orbital. An electron energy loss spectrum has also been recorded from 5.8 to 14.2 eV, under electric-dipole conditions. It confirms the magnitude of the photoabsorption cross section values obtained using the synchrotron radiation and extends the differential and optical oscillator strength values up to 14.2 eV.
Scattering cross sections for low-energy alkali cation +C60 collisions: The relevance of polarization
Authors: Ruiz A. , Bretón J. , Gomez Llorente J. M.
Published: July 2002

Total scattering cross sections for low-energy collisions of C60 fullerene with alkali ions are theoretically estimated using an accurate spherical potential approximation. These cross sections show the relevance of polarization effects. Our results indicate a way in which collisional experimental methods could be used to measure the high polarizabilities of C60 and other fullerenes.
Fine structure of the 4f complexes of ArH and KrH revisited: Quantum defect theory used as a spectroscopic tool
Authors: Jungen Ch. , Roche A. L.
Published: July 2002

The 4f,v=0 manifolds of levels of ArH, ArD, and KrD observed by Dabrowski et al. [J. Mol. Spectrosc. 189, 110 (1998)] and Dabrowski and Sadovskii [J. Chem. Phys. 107, 8874 (1997)] have been reanalyzed using multichannel quantum defect theory. The nondiagonal (l-mixing) quantum defect matrices are partially extracted from the experimental data and are found to be in reasonable agreement with the quantum defects calculated theoretically by Jungen et al. [Phil. Trans. R. Soc. Lond. A 355, 1481 (1997)]. The quantum defect calculations reproduce the observed level fine structure in great detail including nonadiabatic rotational l-uncoupling and electronic l-mixing perturbations.
Transient nucleation in oxide glasses: The effect of interface dynamics and subcritical cluster population
Authors: Gránásy László , James Peter F.
Published: July 2002

To clarify the mechanism of cross-interfacial molecular transport and the role of subcritical cluster population in determining the kinetics of crystal nucleation, cluster dynamics calculations based on viscosity-governed rate coefficients are confronted with experiments on crystal nucleation in six stoichiometric oxide glasses (lithium disilicate, barium disilicate, two soda-lime-silica glasses, wollastonite glass, and lithium diborate). Systematic deviations are observed in the thermal activation of the measured and predicted induction times that lead to a crossover near the glass transition. Below crossover, the viscosity based induction times are higher than the experimental ones, a relation that is reversed at higher temperatures. The differences, that may amount to orders of magnitude far from the crossover temperature, cannot be removed by taking into account the size dependence of the interfacial free energy, the depletion of the monomers, or by enforcing the proper (zero) value of the free energy of monomers. Rather, it appears that while crystal nucleation and viscosity are both diffusion related processes, they are governed by different diffusion modes.
The generalized Heitler–London theory for the H3 potential energy surface
Authors: Kleinekathöfer U. , Tang K. T. , Toennies J. P. , Yiu C. L.
Published: July 2002

A systematic perturbation theory has been developed to analyze the terms contributing to the H3 potential energy surface. Group theory is used to find the irreducible representations of the Hamiltonian matrix elements which then are decoupled to their simplest level. In the case of diatomic molecules, this approach leads naturally to the Generalized Heitler–London (GHL) theory derived previously [K. T. Tang and J. P. Toennies, J. Chem. Phys. 95, 5918 (1991)]. Many previous semi-empirical potential surfaces for the H3 triatomic system including the well known LEPS surface are examined in the light of the present results. In particular, the Cashion–Herschbach (or diatomics-in-molecules without overlap) surface is shown to encompass far more information than previously recognized. The new theory now contains all the terms needed for an exact perturbation calculation of the potential energy surface.
Fourier transform emission spectroscopy and ab initio calculations on OsN
Authors: Ram R. S. , Liévin J. , Bernath P. F.
Published: July 2002

The emission spectrum of OsN has been recorded in the 3000–13 000 cm−1 region using a Fourier transform spectrometer. OsN molecules were excited in an osmium hollow cathode lamp operated with neon gas and a trace of nitrogen. Six bands observed in the 8000–12 200 cm−1 region have been classified into three transitions, a 4Π5/2–X 2Δ5/2, b 4Φ7/2–X 2Δ5/2, and b 4Φ5/2–X 2Δ5/2 with the 0–0 band origins near 8381.7, 11 147.9, and 12 127.2 cm−1, respectively. A rotational analysis of these bands provides the following equilibrium constants for the ground electronic state: ωe=1147.9492(77) cm−1, ωexe=5.4603(36) cm−1, Be=0.493 381(55) cm−1, αe=0.002 753(38) cm−1, and re=1.618 023(91) Å. Ab initio calculations have been performed on OsN and the spectroscopic properties of the low-lying electronic states have been calculated. Our assignments are supported by these calculations. The ground state of OsN has been identified as a 2Δi state consistent with the observations for the isoelectronic IrC molecule [Jansson et al., Chem. Phys. Lett. 4, 188 (1969); J. Mol. Spectrosc. 36, 248 (1970)]. The 1σ22σ21π41δ33σ2 electron configuration has been proposed for the ground state and the configurations for the other low-lying electronic states have also been discussed. This work represents the first experimental or theoretical investigation of the electronic spectra of OsN.
Transition state wave packet study of hydrogen diffusion on Cu(100) surface
Authors: Zhang Dong H. , Light John C. , Lee Soo-Y.
Published: July 2002

The transition state wave packet (TSWP) approach to the thermal rate constant based on the flux-flux autocorrelation function is used to investigate the diffusion dynamics of an H atom on the Cu(100) surface in the uncorrelated hopping regime. The high efficiency of the approach makes it feasible to include up to eight Cu modes explicitly in the time dependent quantum simulation. This is necessary since on the rigid surface the flux-flux autocorrelation function never decays to a negligibly small value to give a converged rate constant. For short times, the Cu modes included dynamically merely have a zero-point-energy effect on the flux-flux autocorrelation function. For longer times, however, the Cu modes absorb the activation energy of the H atom and effectively suppress recrossing of the transition state surface, resulting in convergence of the autocorrelation function and the hopping rate. For this system, recrossing of the transition state surface is minimal with the medium damping present, and the converged hopping rate can be well approximated by the short time behavior of the correlation function on the rigid surface. In addition, we find that the contributions of the excited Cu modes to the hopping rate may be accurately modeled by thermal “transition state” factors. Based on this, a new quantum transition state theory (QTST) is derived. The new theory provides a general way to calculate the approximate quantum correction to the traditional TST. It also provides a systematic and flexible tool to calculate the rate constant at any desired level of accuracy between the traditional TST level and the exact result. Finally, since the surface relaxation due to the presence of the H atom lowers both the energies of H atom in the binding well and on the saddle point almost equally, it only minimally affects the hopping rate, provided the configuration of the surface atoms is fully relaxed initially.
Vesicle adhesion and microemulsion droplet dimerization: Small bending rigidity regime
Authors: Blokhuis Edgar M. , Sager Wiebke F. C.
Published: July 2002

To study the vesicle-substrate unbinding transition and the onset of microemulsion aggregation, we calculate the curvature free energy of a vesicle adhered to a substrate and of two microemulsion droplets forming a dimer. Analytical expressions are derived in the small bending rigidity regime in which the length (k/σ)1/2, constructed from the rigidity constant of bending k and surface tension σ, is small compared to the typical size of the vesicle (droplet), (k/σ)1/2≪R. The leading contribution to the curvature free energy is shown to be proportional to k1/2. The formulas derived are used to understand the experimentally observed aggregation of microemulsion droplets occurring in the direction of vanishing spontaneous curvature. In this way we intend to bridge the gap between the liquid state theories used to describe aggregation processes in microemulsion systems and the bending energy concept originally introduced by Helfrich to describe vesicles shapes and fluctuations as well as phase diagrams of microemulsion systems.
Mixed valence/dipole-bound dianions
Authors: Skurski Piotr , Gutowski Maciej , Simons Jack
Published: July 2002

The possibility of binding two electrons to a molecule utilizing two distinct electron binding sites (i.e., one valence- and one dipole-binding center) is studied using ab initio electronic structure methods. It is found that if the electron binding energy of the dipole-binding site is large enough to overcome the Coulomb repulsion produced by the valence-bound electron, the dianion can be electronically stable with respect to the corresponding monoanion. It is also found that, for reasonable dipole- and valence-binding strengths, the separation between the two sites can be small enough to render the species within the current realm of synthetic possibility. Numerical results are presented for the dianions of LiCN⋯LiCC-PF5 and LiCN⋯LiCN⋯LiCC-PF5, whose vertical electronic stabilities are 0.120 and 0.808 eV, and whose stabilities with respect to fragmentation (i.e., loss of LiCN−) are 3.9 and 36.5 kcal/mol [including zero point energy (ZPE)], respectively.