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9,000 | A Simplified Approach to Optimally Controlled Quantum Dynamics | physics.chem-ph | A new formalism for the optimal control of quantum mechanical physical
observables is presented. This approach is based on an analogous classical
control technique reported previously[J. Botina, H. Rabitz and N. Rahman, J.
chem. Phys. Vol. 102, pag. 226 (1995)]. Quantum Lagrange multiplier functions
are used to preserv... | physics |
9,001 | Influence of the Head Group Size on the Direction of Tilt in Langmuir Monolayers | physics.chem-ph | A model of rods with heads of variable size, which are confined to a planar
surface, is used to study the influence of the head group size on tilted phases
in Langmuir monolayers. Simple free energy considerations as well as exact zero
temperature calculations indicate that molecules with small head groups tilt
towards... | physics |
9,002 | Origin of entropy convergence in hydrophobic hydration and protein folding | physics.chem-ph | An information theory model is used to construct a molecular explanation why
hydrophobic solvation entropies measured in calorimetry of protein unfolding
converge at a common temperature. The entropy convergence follows from the weak
temperature dependence of occupancy fluctuations for molecular-scale volumes in
water.... | physics |
9,003 | Application of a symmetry-adapted algebraic model to the vibratioinal spectrum of methane | physics.chem-ph | The stretching and bending vibrations of methane are studied in the framework
of a symmetry-adapted algebraic model. The model is based on the realization of
the one-dimensional Morse potential in terms of a $U(2)$ algebra. For the 44
observed energies we obtain a fit with a r.m.s. deviation of 1.16 cm$^{-1}$
which is ... | physics |
9,004 | A symmetry-adapted algebraic approach to molecular spectroscopy | physics.chem-ph | We apply a symmetry-adapted algebraic model to the vibrational excitations in
D_3h and T_d molecules. A systematic procedure is used to establish the
relation between the algebraic and configuration space formulations. In this
way we have identified interaction terms that were absent in previous
formulations of the vib... | physics |
9,005 | Optical response of small carbon clusters | physics.chem-ph | We apply the time-dependent local density approximation (TDLDA) to calculate
dipole excitations in small carbon clusters. A strong low-frequency mode is
found which agrees well with observation for clusters C_n with n in the range
7-15. The size dependence of the mode may be understood simply as the classical
resonance... | physics |
9,006 | A general algebraic model for vibrational molecular spectroscopy | physics.chem-ph | We present a symmetry-adapted version of the vibron model and discuss an
application to D_{3h} triatomic molecules: H_3^+, Be_3 and Na_3^+. | physics |
9,007 | Dimensional perturbation theory for vibration-rotation spectra of linear triatomic molecules | physics.chem-ph | A very efficient large-order perturbation theory is formulated for the
nuclear motion of a linear triatomic molecule. To demonstrate the method, all
of the experimentally observed rotational energies, with values of $J$ almost
up to 100, for the ground and first excited vibrational states of CO$_2$ and
for the ground v... | physics |
9,008 | A collaborative theoretical and experimental study of the structure and electronic excitation spectrum of the BAr and B(Ar)2 complexes | physics.chem-ph | We report the investigation of the 3s <- 2p transition in the BAr2 cluster.
In a supersonic expansion of B atoms entrained in Ar, at high beam source
backing pressures we observe several features in the fluorescence excitation
spectrum which cannot be assigned to the BAr diatom. Using BAr(X, B) potential
energy curves ... | physics |
9,009 | He Scattering from Random Adsorbates, Disordered Compact Islands and Fractal Submonolayers: Intensity Manifestations of Surface Disorder | physics.chem-ph | A theoretical study is made on He scattering from three fundamental classes
of disordered ad-layers: (a) Translationally random adsorbates, (b) disordered
compact islands and (c) fractal submonolayers. The implications of the results
to experimental studies of He scattering from disordered surfaces are
discussed, and a... | physics |
9,010 | Comment on ``Boson-realization model for the vibrational spectra of tetrahedral molecules'' | physics.chem-ph | An algebraic model in terms of a local harmonic boson realization was
recently proposed to study molecular vibrational spectra [Zhong-Qi Ma et al.,
Phys. Rev. A 53, 2173 (1996)]. Because of the local nature of the bosons the
model has to deal with spurious degrees of freedom. An approach to eliminate
the latter from bo... | physics |
9,011 | A Simple Method for Calculating Quantum Effects on the Temperature Dependence of Bimolecular Reaction Rates: An Application to $CH_4 + H \to CH_3 + H_2$ | physics.chem-ph | The temperature dependence of the rate of the reaction CH_4+H \to CH_3+H_2 is
studied using classical collision theory with a temperature-dependent effective
potential derived from a path integral analysis. Analytical expressions are
obtained for the effective potential and for the rate constant. The rate
constant expr... | physics |
9,012 | Transition to the Most Probable Kinetic State in a Pre-Steady State System | physics.chem-ph | A system containing a pre-steady state standard (non-autocatalytic) reaction,
with multiple paths, evolves toward a kinetic state with the minimum attainable
activation free energy. Displacement of the path frequency distribution in this
transition was shown to minimise the affinity linked to this change in
activation ... | physics |
9,013 | A computational study of 13-atom Ne-Ar cluster heat capacities | physics.chem-ph | Heat capacity curves as functions of temperature were calculated using Monte
Carlo methods for the series of Ne_(13-n)Ar_n clusters (0 <= n <= 13). The
clusters were modeled classically using pairwise additive Lennard-Jones
potentials. The J-walking (or jump-walking) method was used to overcome
systematic errors due to... | physics |
9,014 | Some theoretical considerations concerning ion hydration in the case of ion transfer between water and 1,2-dichloroethane | physics.chem-ph | Some aspects of direct ion transfer across the water/1,2-dichloroethane are
analyzed using a very simple model based on thermodynamic considerations. It
was concluded that ion solvation by water molecules may occur in some
particular cases in the organic phase, delivering an important contribution to
the Gibbs free ene... | physics |
9,015 | Molecular Modeling of Trifluoromethanesulfonic Acid for Solvation Theory | physics.chem-ph | Reported here are theoretical calculations on the triflic acid and water,
establishing molecular scale information necessary to modeling of the
structure, thermodynamics, and ionic transport of Nafion membranes. To
characterize side chain flexibility and accessibility of the acid proton, free
energies for rotation of b... | physics |
9,016 | Optimized random phase approximations for arbitrary reference systems: extremum conditions and thermodynamic consistence | physics.chem-ph | The optimized random phase approximation (ORPA) for classical liquids is
re-examined in the framework of the generating functional approach to the
integral equations. We show that the two main variants of the approximation
correspond to the addition of the same correction to two different first order
approximations of ... | physics |
9,017 | Protein structure prediction as a hard optimization problem: the genetic algorithm approach | physics.chem-ph | Protein structure prediction can be shown to be an NP-hard problem; the
number of conformations grows exponentially with the number of residues. The
native conformations of proteins occupy a very small subset of these, hence an
exploratory, robust search algorithm, such as a genetic algorithm (GA), is
required. The dyn... | physics |
9,018 | Decoherent Histories and Non-adiabatic Quantum Molecular Dynamics | physics.chem-ph | The role of quantum coherence loss in mixed quantum-classical dynamical
systems is explored in the context of the theory of quantum decoherence
introduced recently by Bittner and Rossky. (J. Chem. Phys. {\bf 103}, 8130
(1995)). This theory, which is based upon the consistent histories
interpretation of quantum mechanic... | physics |
9,019 | Numerical Simulations of Free Radical Reactions | physics.chem-ph | We present an overview of the role of quantum coherence in influencing
nonadiabatic processes in the condensed phase. Equations of motion for mixed
quantum-classical dynamics are derived from the Consistent Histories
interpretation of quantum mechanics. Application of the methods toward
computing the excited state life... | physics |
9,020 | A comparison between algebraic models of molecular spectroscopy | physics.chem-ph | We discuss a symmetry-adapted algebraic (or vibron) model for molecular
spectroscopy. The model is formulated in terms of tensor operators under the
molecular point group. In this way, we have identified interactions that are
absent in previous versions of the vibron model, in which the Hamiltonian is
expressed in term... | physics |
9,021 | Adiabatic passage by light-induced potentials in molecules | physics.chem-ph | We present the APLIP process (Adiabatic Passage by Light Induced Potentials)
for the adiabatic transfer of a wave packet from one molecular potential to the
displaced ground vibrational state of another. The process uses an intermediate
state, which is only slightly populated, and a counterintuitive sequence of
light p... | physics |
9,022 | Facilitated alkali ion transfer at the water 1,2-dichloroethane interphase: Ab-initio calculations concerning alkaline metal cation - 1,10-phenanthroline complexes | physics.chem-ph | A series of calculations on the energetics of complexation of alkaline metals
with 1,10-phenanthroline are presented. It is an experimental fact that the
ordering of the free energy of transfer across the water - 1,2-dichloroethane
interphase is governed by the charge / size ratio of the diferent cations; the
larger ca... | physics |
9,023 | Ion Sizes and Finite-Size Corrections for Ionic-Solvation Free Energies | physics.chem-ph | Free energies of ionic solvation calculated from computer simulations exhibit
a strong system size dependence. We perform a finite-size analysis based on a
dielectric-continuum model with periodic boundary conditions. That analysis
results in an estimate of the Born ion size. Remarkably, the finite-size
correction appl... | physics |
9,024 | Hydrogen molecule in a magnetic field: The lowest states of the Pi manifold and the global ground state of the parallel configuration | physics.chem-ph | The electronic structure of the hydrogen molecule in a magnetic field is
investigated for parallel internuclear and magnetic field axes. The lowest
states of the $\Pi$ manifold are studied for spin singlet and triplet$(M_s =
-1) $ as well as gerade and ungerade parity for a broad range of field
strengths $0 \leq B \leq... | physics |
9,025 | The hydrogen molecule in magnetic fields: The ground states of the Sigma manifold of the parallel configuration | physics.chem-ph | The electronic structure of the hydrogen molecule is investigated for the
parallel configuration. The ground states of the Sigma manifold are studied for
ungerade and gerade parity as well as singlet and triplet states covering a
broad regime of field strengths from B = 0 up to B = 100a.u. A variety of
interesting phen... | physics |
9,026 | Semiclassical theory of vibrational energy relaxation | physics.chem-ph | A theory of vibrational energy relaxation based on a semiclassical treatment
of the quantum master equation is presented. Using new results on the
semiclassical expansion of dipole matrix elements, we show that in the
classical limit the master equation reduces to the Zwanzig energy diffusion
equation. The leading quan... | physics |
9,027 | Vibrational Frequencies of the 2p^2A^"_2 and 3d^2E^" States of the Triatomic Deuterium Molecule | physics.chem-ph | We investigated the vibrational energies in the 2p^2A^"_2 and 3d^2E^" states
of the triatomic deuterium molecule D_3. The experiments were performed using a
fast neutral beam photoionization spectrometer recently developed at Freiburg.
A depletion type optical double-resonance scheme using two pulsed dye lasers
was app... | physics |
9,028 | On the interrelation between Gibbs hypotheses and symmetry postulate | physics.chem-ph | The question of the origin of the Gibbs-factorials is reconsidered. It is
argued, using the example of the Brownian motion, that their appearance in
classical statistical calculations cannot in general be traced back to the
symmetry postulate of quantum mechanics as often assumed. | physics |
9,029 | Algebraic approach to vibrational spectra of tetrahedral molecules: a case study of silicon tetrafluoride | physics.chem-ph | Both the stretch and bend vibrational spectrum and the intensity of infrared
transitions in a tetrahedral molecule are studied in a U(2) algebraic model,
where the spurious states in the model Hamiltonian and the wavefunctions are
exactly removed. As an example, we apply the model to silicon tetrafluoride
SiF$_4$. | physics |
9,030 | U(2) algebraic model applied to stretching vibrational spectra of tetrahedral molecules | physics.chem-ph | The highly excited stretching vibrational energy levels and the intensities
of infrared transitions in tetrahedral molecules are studied in a U(2)
algebraic model. Its applications to silane and silicon tetrafluoride are
presented with smaller standard deviations than those of other models. | physics |
9,031 | Possible Mechanism of Formation and Stability of Anomalous States of Water | physics.chem-ph | We examine the physical processes which are involved in the formation and
stability of the anomalous states of water reported recently. The initial step
of adding a small amount of ionic compound XY to pure water leads to the
formation of water clusters (X^+)(H2O)_n and (Y^-)(H2O)_n with n>>1. The
structure of the clus... | physics |
9,032 | Ultra-low energy scattering of a He atom off a He dimer | physics.chem-ph | We present a new, mathematically rigorous, method suitable for bound state
and scattering processes calculations for various three atomic or molecular
systems where the underlying forces are of a hard-core nature. We employed this
method to calculate the binding energies and the ultra-low energy scattering
phase shifts... | physics |
9,033 | Overtone spectra and intensities of tetrahedral molecules in boson-realization models | physics.chem-ph | The stretching and bending vibrational spectrum and the intensities of
infrared transitions in a tetrahedral molecule are studied in two
boson-realization models, where the interactions between stretching and bending
vibrations are described by a quadratic cross term and by Fermi resonance
terms, called harmonically co... | physics |
9,034 | Quasi-chemical Theories of Associated Liquids | physics.chem-ph | It is shown how traditional development of theories of fluids based upon the
concept of physical clustering can be adapted to an alternative local
clustering definition. The alternative definition can preserve a detailed
valence description of the interactions between a solution species and its
near-neighbors, i.e., co... | physics |
9,035 | Theory, Simulation and Nanotechnological Applications of Adsorption on a Surface with Defects | physics.chem-ph | Theory of adsorption on a surface with nanolocal defects is proposed. Two
efficacy parameters of surface modification for nanotechnological purposes are
introduced, where the modification is a creation of nanolocal artificial
defects. The first parameter corresponds to applications where it is necessary
to increase the... | physics |
9,036 | Multigrid High Order Mesh Refinement Techniques | physics.chem-ph | A method for performing high order mesh refinement multigrid computations is
presented. The Full Approximation Scheme (FAS) multigrid technique is utilized
for a sequence of nested patches of increasing resolution. Conservation forms
are generated on coarse scales by additional defect correction terms which
counter the... | physics |
9,037 | Experimental Indication of Structural Heterogeneities in Fragile Hydrogen-bonded Liquids | physics.chem-ph | We present the first experimental characterization in molecular fragile
glassformers of a 'prepeak that appears significantly below the main peak of
the static structure factor. The temperature and density dependences of this
prepeak are studied via elastic neutron scattering experiments under high
pressure (up to 300 ... | physics |
9,038 | Effect of Anion Triiodide on the Main Phase Transition of Fully Hydrated Dipalmitoylphosphatidylcholine Bilayers | physics.chem-ph | The paper describes the effect of anion I-3 on thermotropic mesomorphism of
fully hydrated dipalmitoylphosphatidylcholine bilayers. The biphasic behaviour
of melting temperature - I-3 concentration dependence and the increase of DELTA
T values with I-3 concentration (DELTA T = melting temperature - freezing
temperature... | physics |
9,039 | A fully ab initio quartic force field of spectroscopic quality for SO_3 | physics.chem-ph | The quartic force field of SO$_3$ was computed fully ab initio using coupled
cluster (CCSD(T)) methods and basis sets of up to $spdfgh$ quality. The effect
of inner-shell correlation was taken into account. The addition of tight $d$
functions is found to be essential for accurate geometries and harmonic
frequencies. Th... | physics |
9,040 | Ab initio thermochemistry beyond chemical accuracy for first-and second-row compounds | physics.chem-ph | By judicious use of extrapolations to the 1-particle basis set limit and
$n$-particle calibration techniques, total atomization energies of molecules
with up to four heavy atoms can be obtained with calibration accuracy (1 kJ/mol
or better, on average) without any empirical correction. For the SCF energy a
3-point geom... | physics |
9,041 | Benchmark ab initio thermochemistry of the isomers of diimide, N_2H_2, using accurate computed structures and anharmonic force fields | physics.chem-ph | A benchmark ab initio study on the thermochemistry of the trans-HNNH,
cis-HNNH, and H$_2$NN isomers of diazene has been carried out using the CCSD(T)
coupled cluster method, basis sets as large as $[7s6p5d4f3g2h/5s4p3d2f1g]$, and
extrapolations towards the 1-particle basis set limit. The effects on
inner-shell correlat... | physics |
9,042 | Ab initio calculations with a nonspherical Gaussian basis set: Excited states of the hydrogen molecule | physics.chem-ph | A basis set of generalized nonspherical Gaussian functions (GGTOs) is
presented and discussed. As a first example we report on Born-Oppenheimer
energies of the hydrogen molecule. Although accurate results have been
obtained, we conclude that H_2 is too 'simple' to allow for a substantial gain
by using nonspherical func... | physics |
9,043 | Instantaneous Pair Theory for High-Frequency Vibrational Energy Relaxation in Fluids | physics.chem-ph | Notwithstanding the long and distinguished history of studies of vibrational
energy relaxation, exactly how it is that high frequency vibrations manage to
relax in a liquid remains somewhat of a mystery. Both experimental and
theoretical approaches seem to say that there is a natural frequency range
associated with int... | physics |
9,044 | Application of time-dependent density functional theory to optical activity | physics.chem-ph | As part of a general study of the time-dependent local density approximation
(TDLDA), we here report calculations of optical activity of chiral molecules.
The theory automatically satisfies sum rules and the Kramers-Kronig relation
between circular dichroism and optical rotatory power. We find that the theory
describes... | physics |
9,045 | Coherent nuclear motion in a condensed-phase environment: Wave-packet approach and pump-probe spectroscopy | physics.chem-ph | A quantum-mechanical Gaussian wave-packet approach to the theoretical
description of nuclear motions in a condensed-phase environment is developed.
General expressions for the time-dependent reduced density matrix are given for
a harmonic potential surface, and the exact quantum dynamics is found for a
microscopic syst... | physics |
9,046 | Molecular Realism in Default Models for Information Theories of Hydrophobic Effects | physics.chem-ph | This letter considers several physical arguments about contributions to
hydrophobic hydration of inert gases, constructs default models to test them
within information theories, and gives information theory predictions using
those default models with moment information drawn from simulation of liquid
water. Tested phys... | physics |
9,047 | A definitive heat of vaporization of silicon through benchmark ab initio calculations on SiF_4 | physics.chem-ph | In order to resolve a significant uncertainty in the heat of vaporization of
silicon -- a fundamental parameter in gas-phase thermochemistry -- $\Delta
H^\circ_{f,0}$[Si(g)] has been determined from a thermochemical cycle involving
the precisely known experimental heats of formation of SiF_4(g) and F(g) and a
benchmark... | physics |
9,048 | Symplectic algorithm for constant-pressure molecular dynamics using a Nose-Poincare thermostat | physics.chem-ph | We present a new algorithm for isothermal-isobaric molecular-dynamics
simulation. The method uses an extended Hamiltonian with an Andersen piston
combined with the Nos'e-Poincar'e thermostat, recently developed by Bond,
Leimkuhler and Laird [J. Comp. Phys., 151, (1999)]. This
Nos'e-Poincar'e-Andersen (NPA) formulation ... | physics |
9,049 | Fermi resonance-algebraic model for molecular vibrational spectra | physics.chem-ph | A Fermi resonance-algebraic model is proposed for molecular vibrations, where
a U(2) algebra is used for describing the vibrations of each bond, and Fermi
resonances between stretching and bending modes are taken into account. The
model for a bent molecule XY_2 and a molecule XY_3 is successfully applied to
fit the rec... | physics |
9,050 | Algebraic description of anharmonic stretching vibrations | physics.chem-ph | A U(2) algebraic model is presented to describe stretching vibrations of
XY$_n$ (n=2, 3, and 4) systems, where anharmonic interactions between the bond
modes are considered. This model in a limit corresponds to an anharmonically
coupled local mode model. As an example, the model for a molecule XY$_4$ is
applied to rece... | physics |
9,051 | Potential of an ionic impurityin a large $^4$He cluster | physics.chem-ph | This paper presents an analysis of the motion of an impurity ion in a
nanometer scale $^4$He cluster. Due to induction forces, ions are strongly
localized near the center of the cluster, with a root mean squared thermal
displacements of only a few \AA. The trapping potential is found to be nearly
harmonic, with a frequ... | physics |
9,052 | Potential of a neutral impurity in a large $^4$He clusters | physics.chem-ph | This paper presents an analysis of the motion of an neutral impurity species
in a nanometer scale $^4$He cluster, extending a previous study of the dynamics
of an ionic impurity. It is shown that for realistic neutral impurity-He
potentials, such as those of SF$_6$ and OCS, the impurity is kept well away of
the the sur... | physics |
9,053 | On spin-rotation contribution to nuclear spin conversion in C_{3v}-symmetry molecules. Application to CH_3F | physics.chem-ph | The symmetrized contribution of E-type spin-rotation interaction to
conversion between spin modifications of E- and A_1-types in molecules with
C_{3v}-symmetry is considered. Using the high-J descending of collisional
broadening for accidental rotational resonances between these spin
modifications, it was possible to c... | physics |
9,054 | Single and Double Resonance Microwave Spectroscopy in Superfluid $^4$He Clusters | physics.chem-ph | Purely rotational transitions of a molecule, such as HCCCN, embedded in large
$^4$He clusters have been detected for the first time. The saturation behavior
shows that, in contrast to previous expectations, the microwave line profiles
are dominated by inhomogeneous broadening mechanisms. Spectral holes and peaks
produc... | physics |
9,055 | Accurate ab initio anharmonic force field and heat of formation for silane, SiH_4 | physics.chem-ph | From large basis set coupled cluster calculations and a minor empirical
adjustment, an anharmonic force field for silane has been derived that is
consistently of spectroscopic quality ($\pm 1 cm^{-1}$ on vibrational
fundamentals) for all isotopomers of silane studied. Inner-shell polarization
functions have an apprecia... | physics |
9,056 | The heat of atomization of sulfur trioxide, SO$_3$ - a benchmark for computational thermochemistry | physics.chem-ph | Calibration ab initio (direct coupled cluster) calculations including basis
set extrapolation, relativistic effects, inner-shell correlation, and an
anharmonic zero-point energy, predict the total atomization energy at 0 K of
SO$_3$ to be 335.96 (observed 335.92$\pm$0.19) kcal/mol. Inner polarization
functions make ver... | physics |
9,057 | Perturbation Theory on Top of Optimized Effective Potential Method | physics.chem-ph | We present a perturbative approach within the scope of Kohn-Sham density
functional theory (DFT). The method is based on the exact exchange-only
optimized effective potential method, and correlation is included via
perturbation expansion using Rayleigh-Schrodinger (RS) perturbation theory
(PT). The correlation potentia... | physics |
9,058 | Orthogonal Linear Combinations of Gaussian Type Orbitals | physics.chem-ph | The set of Gaussian Type Orbitals g(n1,n2,n3) of order (n+1)(n+2)/2, of
common n=n1+n2+n3<=7, common center and exponential, is customized to define a
set of 2n+1 linear combinations t(n,m) (-n<=m<=n) such that each t(n,m) depends
on the azimuthal and polar angle of the spherical coordinate system like the
real or imag... | physics |
9,059 | Light-induced conversion of nuclear spin isomers of molecules | physics.chem-ph | We report on a new phenomenon of molecular nuclear spin isomers conversion in
the field of resonant laser radiation. It is based on the isomer-selective
optical excitation and the difference of conversion rates for excited and
unexcited molecules. We expect the considerable magnitude of the effect for all
molecules whi... | physics |
9,060 | Prototype model for nuclear spin conversion in molecules: The case of "hydrogen" | physics.chem-ph | Using the concept of the so-called quantum relaxation, we build a
semiphenomenological model for orto-para conversion of nuclear spin isomers of
hydrogen-type molecules. | physics |
9,061 | Investigation of $^{4}He_{3}$ trimer on the base of Faddeev equations in configuration space | physics.chem-ph | Precise numerical calculations of bound states of a three-atomic Helium
cluster are performed. The modern techniques of solution of Faddeev equations
are combined to obtain an efficient numerical scheme. Binding energies and
other observables for ground and excited states are calculated. Geometric
properties of the clu... | physics |
9,062 | Optimization of Quantum Monte Carlo Wave Functions Using Analytical Energy Derivatives | physics.chem-ph | An algorithm is proposed to optimize quantum Monte Carlo (QMC) wave functions
based on New ton's method and analytical computation of the first and second
derivatives of the variati onal energy. This direct application of the
variational principle yields significantly low er energy than variance
minimization methods wh... | physics |
9,063 | Spin-Lattice Relaxation in Zero-Magnetic Field Indused by Molecular Reorientations | physics.chem-ph | The stochastic Liouville method is used to analyze the general problem of
spin-lattice relaxation in zero-field for molecules undergoing Markovian
reorientations. | physics |
9,064 | Spin-Lattice Relaxation in Metal-Organic Platinum(II) Complexes | physics.chem-ph | The dynamics of spin-lattice relaxation (slr) of metal-organic Pt(II)
compounds is studied. Often, such systems are characterized by pronounced
zero-field splittings (zfs) of the lowest-lying triplets. Previous expressions
for the Orbach slr process do not allow to treat such splitting patterns
properly. We discuss the... | physics |
9,065 | Density Functional Study of adsorption of molecular hydrogen on graphene layers | physics.chem-ph | Density functional theory has been used to study the adsorption of molecular
H2 on a graphene layer. Different adsorption sites on top of atoms, bonds and
the center of carbon hexagons have been considered and compared. We conclude
that the most stable configuration of H2 is physisorbed above the center of an
hexagon. ... | physics |
9,066 | Performance of discrete heat engines and heat pumps in finite time | physics.chem-ph | The performance in finite time of a discrete heat engine with internal
friction is analyzed. The working fluid of the engine is composed of an
ensemble of noninteracting two level systems. External work is applied by
changing the external field and thus the internal energy levels. The friction
induces a minimal cycle t... | physics |
9,067 | The Physical-Chemical Mechanism of Water Stream Self-Purification | physics.chem-ph | The self-purification process of water streams is studied and the
physical-chemical mechanism of it is determined. The naturally occurring
self-purification process at the Boyne River site is monitored. Experiments at
several creeks and rivers in GTA area that induced the self-purification
process are provided. As a re... | physics |
9,068 | Ortho-Para Conversion in CH3F. Self-Consistent Theoretical Model | physics.chem-ph | A complete theoretical model of the nuclear spin conversion in 13CH3F induced
by intramolecular ortho-para state mixing is proposed. The model contains
parameters determined from the level-crossing spectra of the 13CH3F spin
conversion. This set of parameters includes the ortho-para decoherence rate,
the magnitude of t... | physics |
9,069 | The Flotational Mechanism of Etobicoke Creek's Self-Purification | physics.chem-ph | A flotational mechanism of Etobicoke Creek's self-purification has been
investigated. It is shown that the froth contains a high concentration of
polluting agents. Chemical analyses of the top layer of surface water in
comparison to both before and after froth collector in the course of a year are
provided. As a result... | physics |
9,070 | Phase changes in 38 atom Lennard-Jones clusters. I: A parallel tempering study in the canonical ensemble | physics.chem-ph | The heat capacity and isomer distributions of the 38 atom Lennard-Jones
cluster have been calculated in the canonical ensemble using parallel tempering
Monte Carlo methods. A distinct region of temperature is identified that
corresponds to equilibrium between the global minimum structure and the
icosahedral basin of st... | physics |
9,071 | Phase changes in 38 atom Lennard-Jones clusters. II: A parallel tempering study of equilibrium and dynamic properties in the molecular dynamics and microcanonical | physics.chem-ph | We study the 38-atom Lennard-Jones cluster with parallel tempering Monte
Carlo methods in the microcanonical and molecular dynamics ensembles. A new
Monte Carlo algorithm is presented that samples rigorously the molecular
dynamics ensemble for a system at constant total energy, linear and angular
momenta. By combining ... | physics |
9,072 | The Induced Self-Purification of Creeks and Rivers | physics.chem-ph | The clean-up of several Creeks and Rivers by induction of a self-purification
process was provided. The process took place at all the sites studied with the
up to 100% resulted removal of polluting agents depending on the site and
nature of the contaminant. The self-purification mechanism could be used for
drinking and... | physics |
9,073 | Thermodynamic Equilibrium in Open Chemical Systems | physics.chem-ph | The article presents new model of equilibrium in open chemical systems
suggesting a linear dependence of the reaction shift from equilibrium in
presence of the external thermodynamic force. Basic equation of this model
contains traditional logarithmic term and a non-traditional parabolic term. At
isolated equilibrium t... | physics |
9,074 | A Hybrid Algebraic/Schrödinger Approach to the 2D Franck-Condon Problem | physics.chem-ph | We use recent results regarding the geometry of the U(3) bosonic algebraic
model to motivate a hybrid algebraic-Schr\"odinger approach to the 2D
Franck-Condon problem analogous to 1D approaches. This approach allows one to
analyze bent to linear Franck-Condon transitions of triatomic molecules as well
as clarifies the ... | physics |
9,075 | Electron-hole pairs multiquantum generation mechanizm in the process of excitation of ZnSCdS-Cu by an atomic hydrogen | physics.chem-ph | The luminecsence of ZnSCdS-Cu phosphors of various CdS consentration (0-40%)
is under investigation. The luminescence was exited by hydrogen atoms during
adsorbtion of thermal energy during adsorbtion and impact
recombination-heterogeneous chemiluminenscence(HCL) are discussed. The monotone
lowering of the conductivity... | physics |
9,076 | Temperature, Pressure & Solvent Dependence of Positronium Acceptor Reactions | physics.chem-ph | Positronium (Ps) reaction rates (k) with weak Acceptors (Ac) leading to the
formation of Ps-Ac Complexes show several intriguing features: non-monotonic
temperature dependence of k (departing from the usual Arrhenius paradigm),
considerable variablity of k with respect to different solvents, and anomalies
in response t... | physics |
9,077 | GRECP/MRD-CI calculations of the spin-orbit splitting in the ground state of Tl and of the spectroscopic properties of TlH | physics.chem-ph | The generalized relativistic effective core potential (GRECP) approach is
employed in the framework of multireference single- and double-excitation
configuration interaction (MRD-CI) method to calculate the spin-orbit (SO)
splitting in the $^2P^o$ ground state of the Tl atom and spectroscopic
constants for the $0^+$ gr... | physics |
9,078 | Rotation in liquid $^4$He: Lessons from a toy model | physics.chem-ph | This paper presents an analysis of a model problem, consisting of two
interacting rigid rings, for the rotation of molecules in liquid $^4$He. Due to
Bose symmetry, the excitation of the rotor corresponding to a ring of N helium
atoms is restricted to states with integer multiples of N quanta of angular
momentum. This ... | physics |
9,079 | Convergence improvement for coupled cluster calculations | physics.chem-ph | Convergence problems in coupled-cluster iterations are discussed, and a new
iteration scheme is proposed. Whereas the Jacobi method inverts only the
diagonal part of the large matrix of equation coefficients, we invert a matrix
which also includes a relatively small number of off-diagonal coefficients,
selected accordi... | physics |
9,080 | Extracting molecular Hamiltonian structure from time-dependent fluorescence intensity data | physics.chem-ph | We propose a formalism for extracting molecular Hamiltonian structure from
inversion of time-dependent fluorescence intensity data. The proposed method
requires a minimum of \emph{a priori} knowledge about the system and allows for
extracting a complete set of information about the Hamiltonian for a pair of
molecular e... | physics |
9,081 | Dynamics of Chemical Reactions: Open Equilibrium | physics.chem-ph | Dynamic properties of chemical reactions and appropriate relationships for
open chemical equilibrium are discussed in approach of the chemical dynamics.
New way to calculate composition of chemical systems in open equilibrium, based
on the amended equation for the change of Gibbs' free energy, was exemplified
using rea... | physics |
9,082 | Spontaneous formation and stability of small GaP fullerenes | physics.chem-ph | We report the spontaneous formation of a GaP fullerene cage in ab-initio
Molecular Dynamics simulations starting from a bulk fragment. A systematic
study of the geometric and electronic properties of neutral and ionized GaP
clusters suggests the stability of hetero-fullerenes formed by a compound with
zincblend bulk st... | physics |
9,083 | Hydration of methanol in water. A DFT-based molecular dynamics study | physics.chem-ph | We studied the hydration of a single methanol molecule in aqueous solution by
first-principle DFT-based molecular dynamics simulation. The calculations show
that the local structural and short-time dynamical properties of the water
molecules remain almost unchanged by the presence of the methanol, confirming
the observ... | physics |
9,084 | The Law of Conservation of Energy in Chemical Reactions | physics.chem-ph | Earlier it has been supposed that the law of conservation of energy in
chemical reactions has the following form: DU=DQ-PDV+SUM(muiDN) In the present
paper it has been proved by means of the theory of ordinary differential
equations that in the biggest part of the chemical reactions it must have the
following form: DU=... | physics |
9,085 | The Heats of Dilution. Calorimetry and Van't-Hoff | physics.chem-ph | Earlier it has been found that there is a big difference between heats of
dilution measured by calorimetry and by the Van't-Hoff equation. In the present
paper a reason for that is proposed. Experimental data for dilution of benzene
and n-hexane in water were used. | physics |
9,086 | Application of time-dependent density functional theory to electron-vibration coupling in benzene | physics.chem-ph | Optical properties of symmetry-forbidden pi-pi transitions in benzene are
calculated with the time-dependent density functional theory (TDDFT), using an
adiabatic LDA functional. Quantities calculated are the envelopes of the
Franck-Condon factors of the vibrationally promoted transitions and the
associated oscillator ... | physics |
9,087 | Generalized Heitler-London Theory for H_3: A Comparison of the Surface Integral Method with Perturbation Theory | physics.chem-ph | The generalized Heitler-London (GHL) theory provides a straightforward way to
express the potential energy surface of H_3 in terms of Coulomb and exchange
energies which can be calculated either by perturbation theory or using the
surface integral method (SIM). By applying the Rayleigh-Schroedinger
perturbation theory,... | physics |
9,088 | An interpolation model for the equation of state in binary systems | physics.chem-ph | The new interpolation model of state of binary mixture is investigated. This
model use only two parameters and produce many type of phase diagrams. | physics |
9,089 | Determination of some solubilization parameters with surfactants of egg-yolk lecithin multilamellar vesicles by static light-scattering measurements | physics.chem-ph | Effective surfactant:phospholipid ratios (i.e. molar ratios in the mixed
aggregates, vesicles or micelles) have been determined by static
light-scattering for the interaction of egg-yolk lecithin (EYL) multilamellar
vesicles (MLV) with Triton X-100 (TX-100), sodium deoxycholate (DOCNa) and
cetyltrimethylammonium bromid... | physics |
9,090 | An approximate cooperativity analysis by DSC of phase transitions of DPPC-DOCNa dispersions | physics.chem-ph | The effect of solute, sodium deoxycholate bile salt (DOCNa), on the
cooperativity of ordered-fluid, fosfolipid phase transition has been
investigated by determining of the transition widths in multibilayer
dispersions of the dipalmitoylphosphatidylcholine (DPPC)-DOCNa mixtures. The
DT1/2 values were determined by diffe... | physics |
9,091 | Determination of apparent activating energy of solubilizing MLV-DPPC and MLV-egg-yolk lecithin with surfactants by rectangular optic diffusimetry | physics.chem-ph | It were determinated the apparent activating energy of
dipalmitoylphosphatidylcholine (DPPC) multilamellar liposome (MLV) solubilizing
with sodium deoxycholate (DOCNa) by turbidi-metric measurements and the
apparent activating energy of egg-yolk lecithin (EYL)- MLV solubilizing with
different surfactants (DOCNa, TX-100... | physics |
9,092 | Kinetics of solubilization with Triton X-100 of egg-yolk lecithin bilayers containing cholesterol | physics.chem-ph | The titration solubilization of multilamellar egg-yolk lecithin liposomes
(MLV-EYL) with Triton X-100 was studied by rectangular optical diffusimetric
measurements as a function of cholesterol (Chol) concentration. It was
determinated the variation of optic percentage diffu-sion (per mmol
surfactant), DDif%/mmol TX-100... | physics |
9,093 | Pseudo-time Schroedinger equation with absorbing potential for quantum scattering calculations | physics.chem-ph | The Schroedinger equation with an energy-dependent complex absorbing
potential, associated with a scattering system, can be reduced for a special
choice of the energy-dependence to a harmonic inversion problem of a discrete
pseudo-time correlation function. An efficient formula for Green's function
matrix elements is a... | physics |
9,094 | GRECP/RCC calculation of the spectroscopic constants for the HgH molecule and its cation | physics.chem-ph | Generalized relativistic effective core potential (GRECP) calculations of
spectroscopic constants of the HgH molecule ground and low excited states and
the HgH+ cation ground state are carried out, with correlation included by the
Fock-space relativistic coupled cluster (RCC) method. Basis set superposition
errors (BSS... | physics |
9,095 | Quasi-chemical Theory for the Statistical Thermodynamics of the Hard Sphere Fluid | physics.chem-ph | We develop a quasi-chemical theory for the study of packing thermodynamics in
dense liquids. The situation of hard-core interactions is addressed by
considering the binding of solvent molecules to a precisely defined `cavity' in
order to assess the probability that the `cavity' is entirely evacuated. The
primitive quas... | physics |
9,096 | Overcharging by macroions: above all, an entropy effect | physics.chem-ph | Model macroion solutions next to a charged wall show interface \textit{true
overcharging}, charge reversal and inversion, and layering. Macroion layering
is present, even if the wall or the macroparticle are \textit{uncharged} or if
the wall and macroions are like-charged. An effective long-range attractive
force betwe... | physics |
9,097 | The Electrochemical Reduction of Hydrogen in the Presence of Bisulfate on Platinum(111) | physics.chem-ph | A new model for the intermediate compound of the hydrogen evolution reaction
(HER) is proposed, for the electrochemical reduction of hydrogen in the
presence of bisulfate on platinum(111). The formation of this compound, a
regular 2 dimensional honeycomb ice lattice, occurs by a first order phase
transitions that invol... | physics |
9,098 | Static NLO susceptibilities: testing approximation schemes against exact results | physics.chem-ph | The reliability of the approximations commonly adopted in the calculation of
static optical (hyper)polarizabilities is tested against exact results obtained
for an interesting toy-model. The model accounts for the principal features of
typical nonlinear organic materials with mobile electrons strongly coupled to
molecu... | physics |
9,099 | Vibronic contributions to resonant NLO responses: two-photon absorption in push-pull chromophores | physics.chem-ph | Two-photon absorption (TPA) spectra of push-pull chromophores are described
in terms of a two-state model accounting for electron-vibration coupling.
Vibrations have two main effects in TPA spectra. The most obvious one is the
appearance of a vibrational structure in the spectrum; in this respect we find
large Herzberg... | physics |
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