Interatomic forces,Grüneisen and Anderson-Grüneisen parameters of ionic crystals

The general expression for the Anderson-Grüneisen parameterδ recently derived by Gupta and others, has been used to study the variation ofδ with the Grüneisen parameterγ employing the interaction approach. For this purpose four potential energy functions have been selected. It is found thatδ values evaluated by the modified Varshni-Shukla potential are better than other forms of overlap repulsive interaction. The variation ofδ withγ is also studied by plotting curves betweenδ andγ. The method of least-squares has been employed to yield the best fitted equation.     

The interrelation between the Faraday effect and the inverse Faraday effect in a magnetic medium and the terahertz inverse Faraday effect in single molecule magnets

The interrelation between the Faraday and the inverse Faraday effects when the magneto-dipole interaction of a sample with an electromagnetic wave is essential has been phenomenologically investigated. This investigation was carried out in the spirit of well-known Pitaevsky’s approach. The terahertz inverse Faraday effect in single molecule magnets has been theoretically studied, the conditions favorable for observing this effect have been formulated.     

A study of pion absorption by16O using realistic interactions—I. Twonucleon emission following bound-pion absorption

Matrix element of the Galilean invariant non-relativistic reduction of the pseudoscalar-pseudovector interaction has been calculated assuming the reaction to be a direct process with boundπ ⁻ being absorbed by a correlated pair of nucleons. The Hartree-Fock wavefunctions obtained with the unitary-model-operator approach starting with the realistic nucleon-nucleon interaction have been used forπ-capturing nucleon pair in the initial state. The calculations have been done with and without antisymmetrising the initial state wavefunction of the pion absorbing pair. For the final state nucleon-nucleon interaction has been taken into account. The strongπ-nucleus interaction together with the Coulomb interaction with the finite nuclear size on the bound pion wavefunction are taken into account. Angular distributions of the emitted nucleon-pair, the branching ratios and the total absorption rates are calculated for¹⁶O with and without antisymmetrisation effect. The calculated results are compared with the experimental and other theoretical work.     

Pion absorption by16O using realistic interactions—II: Free pion absorption followed by emission of proton

Matrix element of the Gallilean invariant nonrelativistic reduction of the pseudoscalar-pseudovector interaction has been calculated for free pion absorption by a single nucleon inside the nucleus of¹⁶O. The Hartree-Fock wavefunctions obtained with the unitary-model-operator approach starting with the hard-core nucleon-nucleon interaction have been used for the π-capturing nucleon in the initial state. The initial pion distortion in the presence of nuclear field of the absorbing nucleus prior to its absorption together with the Coulomb interaction with the finite nuclear size has been taken into account. The distortion of the emitted proton in the field of the residual nucleus has also been considered. The differential cross-sections have been obtained and calculated results are compared with the previous experimental and theoretical work.     

Microscopic calculation of proton capture reactions in the mass 60–80 region and its astrophysical implications

Microscopic optical potentials obtained by folding the DDM3Y interaction with the densities from the Relativistic Mean-Field approach have been utilized to evaluate S-factors of low-energy (p, γ) reactions in the mass 60–80 region and to compare with experiments. The Lagrangian density FSU Gold has been employed. Astrophysical rates for important proton capture reactions have been calculated to study the behaviour of rapid proton nucleosynthesis for waiting point nuclei with mass less than A = 80.     

Regge behaviour at high energy and more on boson-fermion interaction

Our approach to the problem of boson-fermion interaction in the conventional RFT stems from a model of super-symmetric version in 2-space and 1 time world. Basically it is stressed here that at super high energy there may not be any distinction between the bosonic and fermionic modes and may be treated on a common footing. Usual renormalization group approach for the vertex function has been adopted and the characteristic functionsβ ₁ andβ ₂ are calculated and the possibility of having stable points in the theory has been studied.     

Velocity-dependent inertial induction—possible explanation for supergravity shift at solar limb

A quantitative model of inertial induction has been earlier proposed by the author which not only results in the exact equivalence of inertial and gravitational masses but also gives rise to an exceedingly small drag dependent on the velocity with respect to the mean rest frame of the universe. This leads to a cosmological redshift in close agreement with the observation. When this velocity drag due to local interaction is considered it is seen that a significant proportion of the secular retardation of the earth’s spin and the moon’s orbital motion can be attributed to this drag. This also resolves the problem of the moon’s close approach to the earth in the past as suggested by a purely tidal friction theory. The observed large secular acceleration of the Phobos is also explained. The present article shows that local interaction also yields a redshift. When applied to the solar radiation it is seen that the observed supergravity shift at the limb can be very satisfactorily explained.     

Unrestricted symmetry-projected Hartree-Fock-Bogoliubov calculations for some PF-shell nuclei

Total binding energies and yrast energy spectra of three selected 1p0f–nuclei have been calculated using an unrestricted Hartree–Fock–Bogoliubov approach with symmetry–projection before the variation. The full 1p0f–shell has been used as single–particle basis and the semi–empirical FPD6 interaction as effective Hamiltonian. The results are compared to those of truncated shell–model calculations performed with the OXBASH code. In the middle of the 1p0f–shell the variational method yields energy gains up to 4.5 MeV and thus proves to be far superior than the conventional truncation methods at least if in the latter only up to about 13000 configurations for each spin–isospin combination are admitted. Received: 15 September 1999     

Interatomic potentials at short range using Madelung’s equations

Interatomic potentials at short range are investigated starting from the united atom electron density. Prior work has utilised time independent Rayleigh-Schr?dinger perturbation theory, adapted to overcome difficulties with convergence of the power series in internuclear distance, and has been confined to diatomic species. This work presents a time dependent approach, based on Madelung’s equations, in which the electron density evolves continuously from that of the united atom to the density of the polyatomic system; no power series is involved, there are no convergence difficulties and the approach is applicable to polyatomic systems. Electronic separation and interaction energies are calculated and compared to previous calculations. Some triatomic and tetratomic arrays of hydrogen atoms are examined and three and four body interaction terms estimated.     

On the second-order phase transition initiated by a strong electron-phonon interaction

A model of a crystal with a strong electron-phonon interaction that initiates a second-order phase transition has been considered. The purpose of the study is to determine the temperature dependence of the thermodynamic potential of the symmetric phase in the temperature range in the immediate vicinity of the transition temperature T _C for this model. The problem has been solved using the quantum Matsubara Green’s function approach, which takes into account the influence of both thermal and quantum fluctuations. It has been demonstrated that fluctuation coherent deformations of the crystal lattice with the same symmetry as in the ordered phase appear to be energetically favorable at T > T _C due to the interaction with the electronic subsystem. The results obtained have made it possible to construct the model of the second-order phase transition near the Curie point T _C.     

Gold nanoparticle induced conformational changes in heme protein

Change of α-helical structure of heme protein (Hb) to a β-sheet and random coil conformation because of the interaction of glycine capped gold nanoparticles (20–60 nm) as observed from attenuation total reflectance, absorption, Fourier transform infra red, and Circular Dichroism spectroscopy has been reported in this article. Upon interaction, protein takes a cylindrical shape of length 12 μm and diameter 0.35 μm as revealed from scanning electron microscopy and transmission electron microscopy. The Selected-Area Electron beam Diffraction pattern shows change of crystalline structure in GNP to amorphous nature with the interaction of Hb.     

Beta-decay of nuclei near the neutron shell <Emphasis Type="Italic">N</Emphasis> = 126

A self-consistent approach to the weak interaction rates is presented. It is based on the generalized energy-density functional method and continuum QRPA. The study has been made of the β-decay total energy releases, half-lives and β-delayed neutron emission branchings for recently identified near-spherical nuclei with charge numbers Z = 76–79 approaching the closed neutron shell at N = 126. Together with our previous calculations near N = 28, 50, 82 this provides an important update to the standard set of weak rates for the r-process modeling, radioactive beam experiments and advanced reactor applications. Within the fully microscopic framework a significant competition is found of the Gamow-Teller and first-forbidden decay contributions to the total half-lives.     

Search for contact interactions in deep inelastic e^+p\to e^+X scattering at HERA

In a search for signatures of physics processes beyond the Standard Model, various eeqq vector contact–interaction hypotheses have been tested using the high– deep inelastic neutral–current scattering data collected with the ZEUS detector at HERA. The data correspond to an integrated luminosity of of interactions at 300 GeV center–of–mass energy. No significant evidence of a contact–interaction signal has been found. Limits at the 95% confidence level are set on the contact–interaction amplitudes. The effective mass scales corresponding to these limits range from 1.7 TeV to 5 TeV for the contact–interaction scenarios considered. Received: 18 May 1999 / Revised version: 14 January 2000 / Published online: 25 February 2000     

Interaction of CdTe Quantum Dots with 2,2-Diphenyl-1-Picrylhydrazyl Free Radical: A Spectroscopic, Fluorimetric and Kinetic Study

The interaction of 2,2-diphenyl-1-picrylhydrazyl (DPPH^●) free radical with thiol-capped CdTe quantum dots (QDs) has been studied by UV–vis spectroscopy, steady state and time resolved fluorescence measurements. Addition of DPPH^● radical to CdTe QDs resulted in fluorescence quenching. The interaction occurs through static quenching as this was confirmed by fluorescence lifetime measurements. Time course absorption studies indicates that DPPH^● may be reduced by interaction with QDs to the substituted hydrazine form (2,2-diphenyl-1-picrylhydrazine) DPPH-H. The mechanism of fluorescence quenching of CdTe QDs by DPPH^● is proposed.     

Luminescent properties of semiconductor composite systems composed of erbium triphthalocyanine molecules and a silicon slot structure in the near-infrared region

Photoluminescence spectra of organic semiconductors based on mono-, bis-, and triphthalocyanine containing erbium as a complexing agent have been obtained in the range of 1–1.8 μm. Comparison of the spectral characteristics has shown that erbium triphthalocyanine has the highest photoluminescence quantum yield at a wavelength of 1.5 μm. To enhance this effect, composite materials based on erbium triphthalocyanine and a silicon slot structure have been synthesized, in which an additional increase in the photoluminescence signal near 1.14 μm has been observed. At the same time, no photoluminescence signal has been observed near the wavelength of 1.5 μm. This can be explained by taking into account the interaction of the erbium triphthalocyanine molecules with the adsorption centers of the silicon matrix.     

On the Lorentz nature of confinement in heavy—light quarkonia

The Lorentz nature of the effective interquark interaction in a heavy—light quarkonium is studied using the vacuum correlators method and the generalized Nambu—Jona-Lasinio potential quark model. An effective scalar interaction is demonstrated to appear self-consistently owing to chiral-symmetry breaking and to dominate for low-lying states in the bound-state spectrum. The relation between such an effective interquark interaction and the QCD string approach is discussed. On the contrary, the upper part of this spectrum is found to be governed by the spatial Lorentz vector interaction which leads to a degeneracy for the states with opposite parity—the so-called restoration of chiral symmetry for excited hadrons. The text was submitted by the author in English.     

Phase transitions as a function of material constants and temperature in intermetallic compounds of the terfenol-D type

A model of magnetic and magnetoelastic properties of intermetallic compounds has been considered with the inclusion of the influence of the “giant” magnetoelastic coupling and the biquadratic exchange interaction. The phase transitions as a function of material constants and temperature have been investigated in the framework of the proposed model. It has been demonstrated that the ferromagnetic and quadrupole phases can be formed in the system under consideration. In this case, the phase transition between these phases is a first-order transition and occurs through the intermediate, i.e., quadrupole-ferromagnetic, state. The dependences of the phase transition temperature on the Heisenberg and biquadratic exchange interaction constants have been obtained for compounds of the terfenol-D type.     

The two-body multipole problem of electrodynamics

A 2-body system composed of two objects having arbitrary distributions of charge and current is discussed. An expression for the velocity dependent potential between these two objects has been obtained in the non-relativistic approximation. This potential consists of two parts viz. a velocity independent scalar potential Φ_eff and another part which is linearly dependent on the relative velocity between the objects. The second part naturally suggests a vector potential A_eff. The potentials have been expanded into multipole terms. It has been found that Φ_eff is a sum of two components viz. Φ_EE and Φ_MM such that each multipole term in Φ_EE represents an interaction between the electric multipoles of the two systems, each term in Φ_MM represents an interaction between their magnetic multipoles whereas each term in A_eff represents an interaction between an electric multipole of one and a magnetic multipole of the other. The results have been applied to the interaction between an electric dipole and a magnetic dipole. The symmetry among the multipole terms in A_eff suggests vanishing vector potential between two identical objects. A corollary of this appears to be absence of spin orbit interaction between two identical particles in the same spin state.     

Study of Relativistic Corrections due to Spin–Orbit Interaction of Fermion–Dyon System Under SU(2) Gauge?Potential in Moduli Space

Investigating energy eigen values of fermion–dyon system under the fundamental representation of SU(2) isospin group, it is shown that the equation contains an extra term, which depicts interaction of spin moment with a vector field. The study of fermion–dyon interaction in non-abelian gauge theory has also been undertaken and the splitting of energy level of the system has been carried out.     

Amplitude dependence of the internal friction and Young’s modulus defect of polycrystalline indium

The dependences of the internal friction and the Young’s modulus defect of polycrystalline indium on the oscillatory strain amplitude have been studied over a wide range of temperatures (7–320 K) and oscillatory strain amplitudes (10⁻⁷−3.5 × 10⁻⁴) at oscillatory loading frequencies of about 100 kHz. It has been revealed that the amplitude dependences of the internal friction and the Young’s modulus defect include stages associated with the interaction of dislocations with point defects and the interdislocation interaction. The temperature range characterized by the formation of point-defect atmospheres (the Cottrell atmospheres) near dislocations in indium has been determined.