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At least 19 recordsLinked to original sources
arXiv2007

Tuning Spontaneous Emission versus Forster Energy Transfer in Biological Systems by Manipulating the Density of Photonic States

We theoretically discuss how to tune the competition between Forster transfer and spontaneous emission in a continuous and nondestructive fashion. The proposed approach is especially suitable for delicate biological systems like light harvesting complexes and fluorescent protein oligomers. We demonstrate that the manipulation of the density of photonic states at the emission frequency of the energy donor results in a change of the quantum efficiencies of the competing energy transfer and spontaneous emission processes. This change will be manifested in a modification of the donor and acceptor emission intensities. Thus, by controlling the local density of photonic states Forster coupled systems can be manipulated and analyzed without the need to physically separate donor and acceptor chromophores for individual analysis, which is of interest, for example, for oligomeric reef coral fluorescent proteins.

physics.chem-ph↗
arXiv2010

The First Law of Thermodynamics and the Thermodynamic Description of Elastic Solids

Historically, the thermodynamic behavior of gasses was described first and the derived equations were adapted to solids. It is suggested that the current thermodynamic description of solid phase is still incomplete because the isothermal work done on or by the system is not counted in the internal energy. It is also suggested that the isobaric work should not be deducted from the internal energy because the system does not do work when it expands. Further more it is suggested that Joule postulate regarding the mechanical equivalency of heat -the first law of thermodynamics- is not universal and not applicable to elastic solids. The equations for the proposed thermodynamic description of solids are derived and tested by calculating the internal energies of the system using the equation of state of MgO. The agreement with theory is good.

physics.chem-ph↗
arXiv2007

Combined Extended Rejoinder to "Extended Comment on "One-Range Addition Theorems for Coulomb Interaction Potential and Its Derivatives" by I. I. Guseinov (Chem. Phys., Vol. 309 (2005), pp. 209-213)"

This article is a thorough critique to the Weniger's comments made to our papers published in prestigious journals in the recent years. A detailed and critical examination of the arguments that led to the suggested comment by Weniger reveals some serious flaws. In our published papers we have shown that the unsymmetrical and symmetrical one-range addition theorems for Slater type orbitals, Coulomb-Yukawa like correlated interaction potentials (CIPs) and their derivatives are derived from the expansions in terms of -ETOs that are complete and orthonormal sets of exponential type orbitals in corresponding Hilbert spaces, where The concrete criticism raised in Weniger's comment against our papers actually touches a very minor aspect of the works that are not relevant at all for the conclusions, which are made. As can be seen from our papers, all of the formulas for different kinds of multicenter integrals over Slater type orbitals with integer and noninteger principal quantum numbers obtained by the use of unsymmetrical and symmetrical one-range addition theorems were tested by computer calculations. We reject the Weniger's personal views about papers published by Guseinov and his coworkers from 1978 to 2006 and respectable referees on one-range addition theorems and multicenter integrals. All claims of inconsistencies and flaws in the theoretical framework are rejected as unfounded. This rejoinder paper contains all of the answers to Weniger's comments.

physics.chem-ph↗
arXiv2013

One-Range Addition Theorems in Terms of -ETOs for STOs and Coulomb-Yukawa Like Correlated Interaction Potentials of Integer and Noninteger Indices

In this study, the one-center expansion formulas in terms of complete orthonormal sets of -exponential type orbitals (-ETOs,) are established for the Slater type orbitals (STOs) and Coulomb-Yukawa like correlated interaction potentials (CIPs) of integer and noninteger indices. These relations are used in obtaining the unsymmetrical and symmetrical one-range addition theorems for STOs and Coulomb-Yukawa like CIPs. The final results are especially useful in the calculations of multicenter multielectron integrals of STOs and CIPs occurring when Hartree-Fock-Roothaan (HFR) and explicitly correlated method are employed.

physics.chem-ph↗
arXiv2007

A Raman spectroscopic study of zircons on micro-scale and Its significance in explaining the origin of zircons

The magmatic and metamorphic zircons were investigated with Raman spectrum microprobe analysis. We found notable differences between these two kinds of zircons exhibited by the variation trend of Raman peak intensity from core to rim of a crystal. In magmatic zircons, the intensity and the ratio H/W of Raman spectrum peaks gradually decrease from core to rim of a crystal, which is produced by an increase in metamictization degree and suggests an increase in U and Th concentrations from core to rim. In metamorphic zircons, there are two kinds of crystals according to their Raman spectra: the first group of zircons exhibits a variation trend opposite to those of magmatic zircons, tending to increase in the Raman peak intensity and H/W value from core to rim of a crystal, which is produced by a decrease in metamictization degree and indicates a decrease of U and Th concentrations from core to rim of a crystal. The second group of zircons exhibits no change in Raman peak intensity and H/W value through a crystal. The data of infrared and Raman spectra of these crystals show that they are well crystallized and have no lattice destruction induced by metamictization, and are thought to crystallize in high temperature stages of metamorphism. During these stages, the U and Th ions have been removed by metamorphic fluids from the parent rocks of these zircons. The other difference between magmatic and metamorphic zircons is the background level of their Raman spectra, which is high and sloped in magmatic zircons, but low and horizontal in metamorphic zircons. The differences between magmatic and metamorphic zircons can be used to identify the genesis of zircons and understand the origin and evolution history of their parent rocks.

physics.geo-ph↗
arXiv2007

Methods of Modern Differential Geometry in Quantum Chemistry: TD Theories on Grassmann and Hartree-Fock Manifolds

Hamiltonian and Schrodinger evolution equations on finite-dimensional projective space are analyzed in detail. Hartree-Fock (HF) manifold is introduced as a submanifold of many electron projective space of states. Evolution equations, exact and linearized, on this manifold are studied. Comparison of matrices of linearized Schrodinger equations on many electron projective space and on the corresponding HF manifold reveals the appearance in the HF case a constraining matrix that involves matrix elements of many-electron Hamiltonian between HF state and double excited determinants. Character of dependence of transition energies on the matrix elements of constraining matrix is established by means of perturbation analysis. It is demonstrated that success of time-dependent HF theory in calculation of transition energies is mainly due to the wrong behavior of these energies as functions of matrix elements of constraining matrix as compared with the exact transition energies

physics.chem-ph↗
arXiv2007

Bichromatically driven double well: Parametric perspective of the control landscape

We numerically construct and study the control landscape of a $(ω,2ω)$ bichromatically driven double well in the presence of strong fields. The control landscape is obtained by correlating the overlap intensities between the floquet states and an initial phase space coherent state with the parametric motion of the quasienergies {\it i.e.,} intensity-level velocity correlator. "Walls" of no control, robust under variations of the relative phase between the fields, are seen in the control landscape and associated with multilevel interactions involving chaotic floquet states.

nlin.CD↗
arXiv2008

Linear Depenedences of Van Der Waals, Covalent and Valence Shell Radii of Atoms of Groups 1a - 8a on their Bohr Radii

An earlier finding that the van der waals radii are related to their de broglie wavelengths for some non-metallic elements has been extended here to show that in fact, they vary linearly with the ground state bohr radii for all the elements of groups 1a to 8 a. Similarly, the valence shell radii and the covalent radii are shown to be linearly dependent on the bohr radii. One table of data and 5 figures have been provided here showing that all the above radii are sums of two lengths, one of which is a multiple of the bohr radius and the other, a positive or negative constant for each group of elements.

physics.gen-ph↗
arXiv2007

Molecular dynamics simulation of nanocolloidal amorphous silica particles: Part II

Explicit molecular dynamics simulations were applied to a pair of amorphous silica nanoparticles of diameter 3.2 nm immersed in a background electrolyte. Mean forces acting between the pair of silica nanoparticles were extracted at four different background electrolyte concentrations. Dependence of the inter-particle potential of mean force on the separation and the silicon to sodium ratio, as well as on the background electrolyte concentration, are demonstrated. The pH was indirectly accounted for via the ratio of silicon to sodium used in the simulations. The nature of the interaction of the counter-ions with charged silica surface sites (deprotonated silanols) was also investigated. The effect of the sodium double layer on the water ordering was investigated for three Si:Na+ ratios. The number of water molecules trapped inside the nanoparticles was investigated as the Si:Na+ ratio was varied. Differences in this number between the two nanoparticles in the simulations are attributed to differences in the calculated electric dipole moment. The implications of the form of the potentials for aggregation are also discussed.

physics.chem-ph↗
arXiv2012

Atmospheric instability as a loss of a metastable equilibrium

General thermodynamic theory of metastable states is used in this short note to try to understand better atmospheric instabilities. It is shown that not only cooling of a cloud can lead to rain, but heating also, especially when there are charged water drops in a cloud (in this case we have rain with lightning). The influence of the global warming on weather is discussed.

physics.ao-ph↗
arXiv2007

An attempt to control a manmade nuclear fusion

A detailed simple model is applied to study a high temperature hydrogen plasma ball. It is assumed that the ions and delocalized electrons are distributed randomly throughout the charged plasma ball (extra/missing charge is assumed to be found in a thin layer on the surface of a ball). The energy of the microscopic electrostatic field around the ions is taken into account and calculated. It is shown in the framework of the model that charged hydrogen plasma ball can be stable as a metastable state, when subjected to external (atmospheric) pressure. Equilibrium radius of a ball, the barrier and the enthalpy of the equilibrium ball are calculated. It looks like the charged plasma ball in a metastable equilibrium should be used to conduct controllable nuclear fusion. Changes in the electric charge can be used to control the volume of a plasma ball.

physics.plasm-ph↗
arXiv2009

Excitation energies from ground-state density-functionals by means of generator coordinates

The generator-coordinate method is a flexible and powerful reformulation of the variational principle. Here we show that by introducing a generator coordinate in the Kohn-Sham equation of density-functional theory, excitation energies can be obtained from ground-state density functionals. As a viability test, the method is applied to ground-state energies and various types of excited-state energies of atoms and ions from the He and the Li isoelectronic series. Results are compared to a variety of alternative DFT-based approaches to excited states, in particular time-dependent density-functional theory with exact and approximate potentials.

physics.chem-ph↗
arXiv2011

The Theory of Uncertainty for Derived Results: Properties of Equations Representing Physicochemical Evaluation Systems

Any physiochemical variable (Ym) is always determined from certain measured variables {Xi}. The uncertainties {ui} of measuring {Xi} are generally a priori ensured as acceptable. However, there is no general method for assessing uncertainty (em) in the desired Ym, i.e. irrespective of whatever might be its system-specific-relationship (SSR) with {Xi}, and/ or be the causes of {ui}. We here therefore study the behaviors of different typical SSRs. The study shows that any SSR is characterized by a set of parameters, which govern em. That is, em is shown to represent a net SSR-driven (purely systematic) change in ui(s); and it cannot vary for whether ui(s) be caused by either or both statistical and systematic reasons. We thus present the general relationship of em with ui(s), and discuss how it can be used to predict a priori the requirements for an evaluated Ym to be representative, and hence to set the guidelines for designing experiments and also really appropriate evaluation models. Say: Y_m= f_m ({X_i}_(i=1)^N), then, although: e_m= g_m ({u_i}_(i=1)^N), "N" is not a key factor in governing em. However, simply for varying "fm", the em is demonstrated to be either equaling a ui, or >ui, or even <ui. Further, the limiting error (d_m^(Lim.)) in determining an Ym is also shown to be decided by "fm" (SSR). Thus, all SSRs are classified into two groups: (I) the SSRs that can never lead "d_m^(Lim.)" to be zero; and (II) the SSRs that enable "d_m^(Lim.)" to be zero. In fact, the theoretical-tool (SSR) is by pros and cons no different from any discrete experimental-means of a study, and has resemblance with chemical reactions as well.

physics.data-an↗
arXiv2008

Collision Cross Section of the J = 2 <- 1 Rotational Transition of CF3CCH due to Higher Order Interactions

The collision cross section of the rotational transition J = 2 <- 1 of 3,3,3-trifluoropropyne, CF3CCH, caused by rare gas perturbers has been determined by investigating transient emission signals of molecular gas samples. From analysis of the pressure dependence of the width of the rotational line J = 2<-1 pressure broadening parameters have been derived for the pure gas and for mixtures with the rare gases He, Ne, Ar, Kr and Xe. The pressure shift parameter for the pure gas sigmas/p = 29.03(12) kHz/Pa also has been obtained. Calculations based on the Anderson-Tsao-Curnutte theory using induction and dispersion interactions for the description of collisions of CF3CCH with He, Ne, Ar, Kr and Xe, respectively, are in qualitative agreement with the experimental results.

physics.chem-ph↗
arXiv2012

Electric double layer in concentrated solutions of ionic surfactants

A simple non-local theoretical model is developed considering concentrated ionic surfactant solutions as regular ones. Their thermodynamics is described by the Cahn-Hilliard theory coupled with electrostatics. It is discovered that unstable solutions possess two critical temperatures, where the temperature coefficients of all characteristic lengths are discontinuous. At temperatures below the lower critical temperature ionic surfactant solutions separate into thin layers of oppositely charged liquids spread across the whole system and the electric potential is strictly periodic. At temperatures between the two critical temperatures separation can occur only near the solution surface thus leading to an oscillatory-decaying electric double layer. At temperatures above the higher critical temperature as well as in stable solutions there is no separation and the electric potential decays exponentially.

cond-mat.soft↗
arXiv2008

Comments on the Hartree-Fock description of the Hooke's atom and suggestion for an accurate closed-form orbital

The ground-state Hartree-Fock (HF) wavefunction of the Hooke's atom is not known in closed form, contrary to the exact solution. The single HF orbital involved has thus far been studied using expansion techniques only, leading to slightly disparate energies. Therefore, the present letter aims at proposing alternative definitions of the HF wavefunction. First, the HF limit is ascertained using a simple expansion, which makes it possible to formulate explicit expressions of HF properties. The resulting energy, 2.038 438 871 8 Eh, is found stable at the tenth digit. Second and more instructive, an analysis of the Hartree equation makes it possible to infer a remarkably simple and accurate HF orbital, leading to an energy exceeding by 5.76 10-7 Eh only the above HF limit. This orbital makes it possible to obtain (near) Hartree-Fock properties in closed-form, which in turn enables handy comparisons with exact quantities.

physics.atom-ph↗