共查询到20条相似文献,搜索用时 15 毫秒
1.
N. I. Selivanov L. G. Samsonova V. Ya. Artyukhov T. N. Kopylova 《Russian Physics Journal》2011,54(5):601-606
Results of quantum-chemical studies of the nile red (NR) molecule and its protonated structures by the INDO/S method are presented.
It is demonstrated that the best agreement between the calculated and experimental data is obtained for the flat molecule
in the ground electron state. Energies of the strongest singlet and triplet electronic states, molecular nature of these states,
transition oscillator force, dipole moments in the ground and excited states, electron density distribution around atoms and
molecular fragments in the S0 and S1 states, and rate constants of radiative, internal, and intercombination conversion are presented for the NR molecule and
its protonated structures. The most probable NR protonation centers are analyzed using the molecular electrostatic potential
(MESP) method. It is established that the reaction of proton addition to the NR molecule proceeds at the cyclic nitrogen atom.
As demonstrated the results of quantum-chemical calculations, low fluorescent properties of the protonated NR structures (with
a quantum yield of 4%) are due to a high rate of the S1 – T4 intercombination conversion. 相似文献
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A very simple quantum chemical model is proposed to simulate the effect of external forces acting on a single molecule. It involves optimising the geometry of a molecule with an external force applied to selected nuclei. This approach is used to investigate conformational transitions of the pyranose ring, which have been the subject of several atomic force microscopy (AFM) experiments, and to generate a number of previously unknown isomers of azobenzene. 相似文献
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《Nuclear Physics B》1988,307(4):883-908
We present new predictions for the detection of supersymmetric dark matter via its annihilation in the Sun and elastic scattering off heavy nuclei in the laboratory. Our predictions include many effects found in realistic models such as non-degenerate left- and right-squark masses, unequal supersymmetric Higgs v.e.v.s and photino/higgsino/zino mixing in the lightest supersymmetric particle (LSP). Hadronic matrix elements are estimated using either the naive quark model or the EMC measurement of the spin-dependent proton structure function and perturbative QCD. Nuclear matrix elements are calculated using the shell-model and the small effects of quark vector current operators are discussed. Previous predictions for the elastic LSP-proton scattering cross section, and hence for high energy solar neutrinos from LSP annihilations, are reduced by the EMC estimate and by unequal squark masses, but may be increased by unequal Higgs v.e.v.s. Previous predictions for elastic photino scattering off nuclei with unpaired neutrons are greatly enhanced by the EMC estimate. As a result, preferences for the nuclei to be used in laboratory experiments to detect supersymmetric dark matter may be greatly altered. 相似文献
7.
P. Moskovkin S. Pisov M. Hou C. Raufast F. Tournus L. Favre V. Dupuis 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,43(1-3):27-32
Model and real cobalt-platinum alloy clusters are compared in terms of structure, composition and segregation. Canonical and
semi grand canonical Metropolis Monte Carlo simulations are performed to model these clusters,
using embedded atom (EAM) and modified embedded atom (MEAM) potentials. All
of them correctly predict the bulk L12 Co3Pt and CoPt3
structures as well as the L10 CoPt phase. However, the lattice
parameters, phase stability and the L10-fcc order-disorder transition
temperature are at variance. Segregation predictions with EAM and MEAM
potentials are contradictory. Experimentally, mixed clusters with various
compositions were deposited by Low Energy Cluster Beam on amorphous carbon
at room temperature. Their size distribution, crystalline structure and
composition were examined by Transmission Electron Microscopy (TEM).
Clusters with the same size distributions were modelled. Both experiment and
modelling show their crystallographic parameters to continuously correspond
to the fcc CoPt chemically disordered phase. Diffraction measurements
indicate surface segregation of the specie in excess, in agreement with EAM
predictions for the Co-rich phase. The consequences on magnetic properties
are discussed. 相似文献
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Superconductivity and ferromagnetic ordering are two antagonistic types of ordering, and their mutual influence leads to many interesting phenomena which have been studied recently in ternary compounds. Theoretical analysis of ferromagnetic materials which are type II superconductors near the superconducting transition point T cl shows that they become type I near the magnetic transition point T M. The proposed theory constructed for the case T M « T cl predicts the formation of a transverse domain-like (DS phase) magnetic structure below T M. The electronic spectrum appears to be gapless in the DS phase of clean compounds with a re-entrant transition. The change from type II to type I behaviour as the sample is cooled to T M has been observed in ErRh4B4. Experimental data for HoMo6S8, HoMo6Se8 and ErRh4B4 give evidence for the coexistence of super-conductivity and non-uniform magnetic ordering below T M. Mutual influence of superconducting and magnetic orderings is also studied. 相似文献
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Wolfgang Vollmann 《Molecular physics》2013,111(2):395-406
Starting from the equation of motion for the density matrix, ENDOR spectra are computed for a biradical for the first time. The model biradical carries two electronic spins S = 1/2 and two nuclear spins I = 1/2. The relaxation operator is calculated ab initio for three distinct relaxation mechanisms. These mechanisms are the modulation of the isotropic exchange interaction, the hyperfine tensor and the zero-field splitting tensor. The dependence of the ENDOR effect on the amplitudes of the radiofrequency and microwave fields, on the strength of the zero-field splitting tensor, and on the correlation times of the correlation functions is investigated. 相似文献
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Summary The formation of NaNe molecule has been detected in a hollow cathode lamp containing traces of sodium and neon using the optogalvanic
technique. Two broad continuum peaks have been observed in the structure. They have been analysed to result due to transitions
{Na(3s) + Ne(2p
6)}2Σ1→ →{Na*(3p) + Ne(2p
6)}2Π,2Σ and {Na*(3p) + Ne(2p
6)}2Π,2Σ→{Na*(5s) + Ne(2p
6)}2Σ1. A third peak in between these is probably due to a two-photon transition from 3s→5s of Na in NaNe.
The authors of this paper have agreed to not receive the proofs for correction. 相似文献
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The possibility of computer simulation of the fluorescence spectrum of an actual system of single molecules, whose initial isomeric structure is photochemically transformed as a result of a radiationless resonance transition, is demonstrated.Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 71, No. 6, pp. 740–744, November–December, 2004.This revised version was published online in April 2005 with a corrected cover date. 相似文献
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Using the Hartree-Fock-Roothaan method, symmetric potential energy and dipole moment functions have been obtained for the ground state of the water molecule. These functions were transformed and analyzed in terms of the normal symmetric stretching (v1) and bending (v2) coordinates for the calculation of i.r. transition matrix elements. There is satisfactory agreement between this work and the experimental values for the transition matrix element of the v2 fundamental. However, a discrepancy of a factor of 2.5 is observed between calculated and experimental matrix elements for the v1 fundamental. 相似文献
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The low lying electronic states of the FeSi molecule have been investigated by performing complete active space self-consistent field (CASSCF) and multireference single and double excitation configuration interaction (MRSDCI) calculations. Although the classification of the ground state was not established, the results of the MRSDCI calculations suggest that the ground state of FeSi is 3Δ, and the lowest excited state is 5Π whose transition energy is 0.36 eV including the Davidson-type Q correction. The R e given by MRSDCI with Q correction is 2.23 Å for 3Δ and 2.19 Å for 5Π. The spectroscopic constants and dipole moments of the low lying 5Δ and 3Π states as well as the 3Δ and 5Π states are also evaluated. The bonding nature of FeSi in the 3Δ state is discussed in comparison with the FeC molecule. 相似文献
14.
F. Dowell 《Journal of statistical physics》1991,62(5-6):1059-1071
This paper presents a summary of unique highly nonlinear static and dynamic theories for chain molecules (actually, for almost any kind of organic molecule), including the first superstrong polymers. These theories have been used to predict and explain (1) the physical self-assembly (self-ordering) of specific kinds of molecules into liquid crystalline (LC) phases (i.e., partially ordered phases) and (2) the diffusion of these molecules in various LC phases and the isotropic (I) liquid phase.By acceptance of this article, the publisher recognizes that the U. S. Government retains a nonexclusive, royality-free license to publish or reproduce the published form of this contribution, or to allow others to do so, for U.S. Government purposes. 相似文献
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Piotr Łobacz Patryk Jasik Józef E. Sienkiewicz 《Central European Journal of Physics》2013,11(9):1107-1114
Semi-empirical adiabatic potential energy curves of highly excited states of the KRb molecule are calculated as a function of the internuclear distance R over a wide range from 3 to 150 a 0. The diatomic molecule is treated as an effective two-electron system by using the large core pseudopotentials and core polarization potentials. All calculations are performed by using the nonrelativistic CASSCF/MRCI method with accurate basis set functions. The spectroscopic constants of the calculated electronic states agree well with experimental data, including the recent ones from Lee et al., and with available theoretical results. 相似文献
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Theoretical predictions for the Bardeen-Cooper-Schrieffer-Bose-Einstein condensation crossover of trapped Fermi atoms are compared with recent experimental results for the density profiles of 6Li. The calculations rest on a single theoretical approach that includes pairing fluctuations beyond mean-field. Excellent agreement with experimental results is obtained. Theoretical predictions for the zero-temperature chemical potential and gap at the unitarity limit are also found to compare extremely well with Quantum Monte Carlo simulations and with recent experimental results. 相似文献
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Progress in various fields of microscopy techniques brought up enormous possibilities to study the photosynthesis down to the level of individual pigment-protein complexes. The aim of this review is to present recent developments in the photosynthesis research obtained using such highly advanced techniques. Three areas of microscopy techniques covering optical microscopy, electron microscopy and scanning probe microscopy are reviewed. Whereas the electron microscopy and scanning probe microscopy are used in photosynthesis mainly for structural studies of photosynthetic pigment-protein complexes, the optical microscopy is used also for functional studies. 相似文献
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L. V. Grigorenko 《Physics of Particles and Nuclei》2009,40(5):674-714
In this paper the survey of the current state of investigation of two-proton radioactivity and related processes (three-body
decays) is presented. The three-body (core + p + p) theoretical model of two-proton radioactivity based on the hyperspherical harmonics method and approximate boundary conditions
of the Coulomb’s three-body problem specific for the studied class of processes is considered. The predictions for lifetimes
and correlations of decay products for “promising” two-proton emitters are given. Astrophysical applications of the theory
of two-proton radioactivity are discussed. 相似文献
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《Comptes Rendus Physique》2003,4(9):993-1008
Mechanical properties of carbon nanotubes are discussed based on recent advances in both modeling and experiment. To cite this article: R.S. Ruoff et al., C. R. Physique 4 (2003). 相似文献