共查询到20条相似文献,搜索用时 31 毫秒
1.
Andrea Alparone 《Molecular physics》2014,112(13):1755-1760
Static and dynamic electronic and vibrational first-order hyperpolarisabilities (β) of the lowest energy neutral adenine tautomers (amine forms A7 and A9) were obtained in gaseous and aqueous phases by using Hartree–Fock, Møller–Plesset second-order and fourth-order perturbation theory (MP2 and MP4-SDQ) and conventional and long-range corrected density functional theory methods with the Dunning's correlation-consistent cc-pVDZ, aug-cc-pVDZ, aug-cc-pVTZ and d-aug-cc-pVDZ basis sets. Frequency-dependent properties were calculated at the characteristic wavelength of the Nd:YAG laser (1064 nm) for the second harmonic generation and electro-optical Pockels effect nonlinear optical processes. Solvent effects were introduced under the polarised continuum model approximation. The electronic βe values of the investigated isomers are noticeably affected by the theoretical level, basis set and solvation. In vacuum, the static and dynamic βe values of A9 are greater than the corresponding data of A7, whereas the contribution of the solvent significantly enhances the hyperpolarisabilities of the A7 tautomer, resulting in βe(A9)/βe(A7) ratios between 0.5 and 0.6. The vibrational hyperpolarisabilities of the adenine tautomers are quite close to each other. 相似文献
2.
G. Zet 《Foundations of Physics》1990,20(1):111-117
A model for gauge theories over a compact Lie group is described using R × S3 as background space. The U(1) and SU(2) gauge theories are considered as particular examples, and a comparison with other results is given. Our results differ from those of Carmeli and MalinFound. Phys.
16, 791 (1986);17, 193 (1987)] by a supplementary term in the curvature tensor due to the noncommutativity of derivatives used on R × S3 space. Some observations about supersymmetry and gravity on R × S3 space are also given. 相似文献
3.
The dynamics of a point-like relativistic particle with respect of the proper time is formulated on the hyperboloid p
2
0–p
2=M
2
c
2. The Hamilton-Jacobi equations on the hyperboloid are derived for the particles with mass (M
2=m
2, m>0), for the particles with zero-mass (M=0, m>0), and for the neutrino. It is shown, in a certain factorization of the momentum, the model can be identified with Nambu's three-dimensional phase space formalism. A first quantized version of the model is formulated according to a canonical scheme of quantization (Schrödinger quantization scheme). 相似文献
4.
A theoretical study is reported of the vibrations associated with a Ni3+ impurity charged with respect to the ZnO lattice. The calculations were made by a recursive method in terms of the shell
model for vibrations with different symmetries. The vibronic structure observed in the spectra of d-d intracenter transitions in the Ni3+ impurity has been interpreted using model calculations.
Fiz. Tverd. Tela (St. Petersburg) 41, 618–622 (April 1999) 相似文献
5.
Abstract This paper presents a new theoretical technique for the study of defects in crystals. The methods is based on an ab-initio Hartree-Fock perturbed-cluster (PC) scheme1. A prerequisite for this technique is the availability of a model for the host, perfect crystal, that must be obtained with the same Hamiltonian and the same computational conditions (basis set, accuracy etc.). This information is provided by CRYSTAL, an ab-initio periodic Hartree-Fock code2. 相似文献
6.
Y. Koide 《The European Physical Journal C - Particles and Fields》2007,52(3):617-623
Stimulated by Ma’s idea, which explains the tribimaximal neutrino mixing by assuming an A4 flavor symmetry, a lepton mass matrix model is investigated. A Frogatt–Nielsen-type model is assumed, and the flavor structures
of the masses and mixing are caused by the VEVs of SU(2)L singlet scalars φi
u and φi
d (i=1,2,3), which are assigned to 3
and (1
,1
’,1
”) of A4, respectively. Possible charged lepton and neutrino mass spectra and mixing are investigated. 相似文献
7.
S. A. Karamov 《Physics of the Solid State》1998,40(2):176-179
A study is made of some characteristics of phonon-free pairing of hybridized p and d electrons in planar NiB complexes in the presence of strong short-range Hubbard repulsion. A generalized Hubbard model is
used to calculate the superconductivity phase diagram as a function of the degree of underfilling of the 2p
6 and 3d
10 shells in NiB complexes. The phase region of states having the highest superconducting transition temperatures is established.
Fiz. Tverd. Tela (St. Petersburg) 40, 198–201 (February 1998) 相似文献
8.
L. I. Buravov 《Russian Physics Journal》2009,52(1):25-32
Masses of a number of elementary particles are calculated on the basis of the model suggested in [1] with the use of one parameter. In this model, an electron is considered as an electric cloud enclosed inside an elastic
lepton shell, electron neutrino ν
е
is considered as an elastic lepton shell contracted to a minimal size, and muon, pion and kaon are considered as resonators
for quanta of virtual neutrinos excited inside the elastic lepton shell. The number and type of these quanta are determined
from the decay scheme for μ, π, and K: 2 for the muon (ν
е
and ), 3 for the pion (ν
е
,
ν
μ, and ), and at least 21 for the kaon. The model allows mass ratios approximating the experimental data for these particles to be
obtained for the first time, with the ratio of μ and е masses equal to (6πℏс/е
2)2/3 ≅ 188, the ratio of π
0 and μ masses equal to (3/2)2/3, and the ratio of K
0 and π
0
equal masses to 72/3. The calculated e, μ
,
π
0, and K
0 masses are in the 0.547:105.707:134.963:493.87 (MeV) ratios (normalized by the neutral pion mass). This is in good agreement
with the available experimental data. The mass ν
е
(≅ 0.02 eV) is also estimated in this model, and the variety of K-meson decay schemes is naturally explained as a result of the variety of excited intrinsic neutrino field structures with
the same energy.
Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 1, pp. 23–29, January, 2009. 相似文献
9.
PbTe/CdTe量子点是一类新型异系低维结构材料,实验发现具有强的室温中红外光致发光现象.为研究这一材料体系的发光特性,建立了理论模型,计算了PbTe/CdTe量子点的光学跃迁和增益.模型基于k·p包络波函数方法并考虑了PbTe能带结构的各向异性.分析了量子点光学增益与量子点尺寸、注入载流子浓度的关系.结果表明,当注入载流子浓度在(0.3—3)×1018cm-3范围时,尺寸为15—20nm的量子点可以产生
关键词:
PbTe/CdTe量子点
光学增益
铅盐矿半导体 相似文献
10.
Timothy H. Boyer 《Foundations of Physics》2002,32(1):1-39
A fundamentally new understanding of the classical electromagnetic interaction of a point charge and a magnetic dipole moment through order v
2
/c
2
is suggested. This relativistic analysis connects together hidden momentum in magnets, Solem's strange polarization of the classical hydrogen atom, and the Aharonov–Bohm phase shift. First we review the predictions following from the traditional particle-on-a-frictionless-rigid-ring model for a magnetic moment. This model, which is not relativistic to order v
2
/c
2
, does reveal a connection between the electric field of the point charge and hidden momentum in the magnetic moment; however, the electric field back at the point charge due to the Faraday-induced changing magnetic moment is of order 1/c
4
and hence is negligible in a 1/c
2
analysis. Next we use a relativistic magnetic moment model consisting of many superimposed classical hydrogen atoms (and anti-atoms) interacting through the Darwin Lagrangian with an external charge but not with each other. The analysis of Solem regarding the strange polarization of the classical hydrogen atom is seen to give a fundamentally different mechanism for the electric field of the passing charge to change the magnetic moment. The changing magnetic moment leads to an electric force back at the point charge which (i) is of order 1/c
2
, (ii) depends upon the magnetic dipole moment, changing sign with the dipole moment, (iii) is odd in the charge q of the passing charge, and (iv) reverses sign for charges passing on opposite sides of the magnetic moment. Using the insight gained from this relativistic model and the analogy of a point charge outside a conductor, we suggest that a realistic multi-particle magnetic moment involves a changing magnetic moment which keeps the electromagnetic field momentum constant. This means also that the magnetic moment does not allow a significant shift in its internal center of energy. This criterion also implies that the Lorentz forces on the charged particle and on the point charge are equal and opposite and that the center of energy of each moves according to Newton's second law F=Ma where F is exactly the Lorentz force. Finally, we note that the results and suggestion given here are precisely what are needed to explain both the Aharonov–Bohm phase shift and the Aharonov–Casher phase shift as arising from classical electromagnetic forces. Such an explanation reinstates the traditional semiclassical connection between classical and quantum phenomena for magnetic moment systems. 相似文献
11.
I. V. Gaidaenko A. V. Novikov V. A. Novikov A. N. Rozanov M. I. Vysotsky 《JETP Letters》1998,67(10):761-765
The large top-quark mass is responsible for the enhancement of the oblique radiative corrections in SUSY models. We present
analytical formulas for these corrections to the W-boson mass m
W
and to the Z
l
+
l
−-coupling constants. A comparison with the result of the standard model fit is made.
Pis’ma Zh. éksp. Teor. Fiz. 67, No. 10, 723–726 (25 May 1998)
Published in English in the original Russian journal. Edited by Steve Torstveit. 相似文献
12.
The electron impact ionization cross-sections of mono- and di-positive ionic targets are calculated using a second version
of the modified binary-encounter-dipole (MBED) model, previously reported [M A Uddinet al, J. Phys.
B37, 1909 (2004)]. The present version differs from the previous one in the scale factor of the Burgess denominator and is applicable
to targets with chargesq = 1 and 2. The MBED in the present form is found to work well for 11 ionic targets ranging from Be+ to K+ and complements its previous version valid for targets withq s> 2 相似文献
13.
E. A. Shapoval 《JETP Letters》1998,67(5):376-381
A model of strongly coupled electrons on a square lattice with attraction of the electrons to nearest-neighbor and next-nearest
neighbor lattice sites is studied. For this model, the phase diagrams containing d
x
2−y
2, d
xy, and (d
x
2−y
2+id
xy) states are constructed in the variables temperature versus chemical potential for different ratios of the corresponding
potentials.
Pis’ma Zh. éksp. Teor. Fiz. 67, No. 5, 356–360 (10 March 1998) 相似文献
14.
A static model of a critically polarized ceramic is used to analyze the behavior of the piezocoefficient d
33 of lead titanate zirconate ceramic exposed to a longitudinal compressive stress σ and a quantitative analysis is made of the 90° and 180° domain reorientations. It is shown that for TsTG-83G ceramic a 180°
antiparallel domain structure forms at compressive stresses σ>108 N/m2.
Zh. Tekh. Fiz. 69, 46–49 (June 1999) 相似文献
15.
A quasiharmonic model calculation for non-markovian far-infrared spectra of HCl in Kr and Xe liquids
The far-infrared spectra (0–200 cm?1) of dilute solutions of HCl in liquid Kr and Xe have been calculated by applying of a non-markovian spectral theory called PTOC (partial time ordering cumulants) and by using a quasiharmonic model for the liquid structure recently reported by us (A. Calvo Hernández et al., 1987, J. chem. Phys., 86, 4597) and successfully applied to HCl?Ar solution (Ibid., 86, 4607). The bath correlation functions which appear in the spectral theory involve a reduced set of parameters regarding both the HCl?Kr and HCl?Xe interactions and the liquid structure. From comparison between theoretical and experimental spectra it is possible to deduce quantitative values for the above parameters. The pronounced rotational fine structure of the experimental spectra for HCl in Kr and Xe liquids is quite well explained by the actual model. 相似文献
16.
The quasi-elastic contribution of the nuclear inclusive electron scattering model developed in [A. Gil, J. Nieves, and E.
Oset: Nucl. Phys. A 627 (1997) 543] is extended to the study of electroweak charged current induced nuclear reactions at intermediate energies of
interest for future neutrino oscillation experiments. The model accounts for long-range nuclear (RPA) correlations, final
state interaction and Coulomb corrections. RPA correlations are shown to play a crucial role in the whole range of neutrino
energies, up to 500 MeV, studied in this work. Predictions for inclusive muon capture for different nuclei, and for the reactions
12C(ν
μ
, μ
−)X and 12C(ν
e, e−)X near threshold are also given.
Presented by M. Valverde at the Workshop on calculation of double-beta-decay matrix elements (MEDEX’05), Corfu, Greece, September
26–29, 2005. 相似文献
17.
Dynamics of electron-hole plasma in semiconductor opening switches for ultradense currents 总被引:2,自引:0,他引:2
A physicomathematical model for calculating the dynamics of the electron-hole plasma in semiconductor opening switches for
ultradense currents is developed. The model takes account of the real doping profile of a semiconductor p
+-p-n-n
+ structure and the following elementary processes in the electron-hole plasma: current-carrier diffusion and drift in high
electric fields, recombination on deep impurities and Auger recombination, and collisional ionization in a dense plasma. The
electrical pumping circuit of the opening switch is calculated by solving the Kirchhoff equations. The motion of the plasma
in the semiconductor structure is analyzed on the basis of the model. It is shown that for ultrahigh pumping levels the interruption
of the current in the opening switch occurs in the heavily doped regions of the p
+-p-n-n
+ structure and is due to saturation of the particle drift velocity in high electric fields.
Zh. Tekh. Fiz. 67, 64–70 (October 1997) 相似文献
18.
R. Ramakumar K. Yamaji 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,24(1):71-75
A simple model is developed to understand superconductivity in α
′
-TTF[Pd(dmit)2]2. We include electron-intra molecular and intermolecular phonon interactions as the mechanism of superconductivity. Intramolecular vibrations included are the eight symmetric Ag modes of the Pd(dmit)2 molecule. Intermolecular vibrations included are the longitudinal acoustic and transverse acoustic (LA and TA) modes of the Pd(dmit)2 column. All the electron-phonon coupling constants are calculated from first principles. We find that largest el-intramolecular vibration coupling is to the Ag mode with the highest frequency (1449 cm-1). The el-intermolecular coupling to the LA mode is found to be larger than the total el-intramolecular couplings. We also find el-(TA)phonon coupling to be at least an order of magnitude smaller than el-(LA)phonon coupling.
Estimate of superconducting transition temperature is comparable to experimental result. We also provide a detailed discussion,
employing the results of recent numerical calculations on two-chain Hubbard model and the specific material parameters, on
the relative importance of el-ph and Coulomb-origin mechanisms of superconductivity in α
′
-TTF[Pd(dmit)2]2 and TTF[Ni(dmit)
2
]
2
.
Received 29 March 2001 and Received in final form 7 August 2001 相似文献
19.
M. Celasco R. Eggenhöffner 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,23(4):415-419
A dynamical percolative model explaining the universality of 1/
f
γ
noise is reported. Exponents γ ranging from 0 to 2 are obtained under the hypothesis that noise originates from random switching events between two ON-OFF
states in elemental parts (switchers) of a physical system. The usual noise behaviour with γ very close to 1 in an arbitrarily wide frequency range is obtained assuming a statistical distribution of switcher relaxation
time τ proportional to τ
-1
, as in McWhorter's model. The impact of these results with respect to recent self-organised criticality models is discussed.
Received 6 November 2000 and Received in final form 22 May 2001 相似文献
20.
Using the loop equations we find an explicit expression for genus 1 correction in hermitian two-matrix model in terms of holomorphic objects associated to spectral curve arising in large N limit. Our result generalises known expression for F1 in hermitian one-matrix model. We discuss the relationship between F1, Bergman tau-function on Hurwitz spaces, G-function of Frobenius manifolds and determinant of Laplacian over spectral curve.Mathematics Subject Classifications. 15A52, 34M55. 相似文献