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基于相对论平均场理论(RMF),采用TM1以及有效超子-核子和超子-超子相互作用,首先研究了16O和ΛΛ18O的单粒子能级受超子的影响情况,发现超子的加入使得核子能级能量降低.其次基于相对论无规位相近似方法 (RRPA),自洽地计算了16O和ΛΛ18O同位旋标量巨单极和四极共振态.发现相比于16O各巨共振的响应函数,超核的响应函数会发生改变.研究表明:这种改变主要来自于超子的加入导致的核子单粒子能级的改变,以及超子粒子-空穴组态跃迁的贡献,而超子-超子剩余相互作用对单极和四极共振在低能区的响应函数的影响比较小,特别对高能区的响应函数基本没有影响. 相似文献
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在相对论平均场的基态上自洽的相对论无规位相近似(RRPA)理论框架下,研究稳定核和不稳定核的巨共振性质.研究了稳定核208Pb,144Sm,116Sn,90Zr,40Ca,16O和不稳定核Ca同位素链同位旋标量和同位旋矢量集体巨共振激发,并讨论了Dirac海负能核子态和矢量介子空间分量对核的巨共振性质的影响.研究的结果表明,Dirac海负能核子态和矢量介子空间分量对同位旋标量激发有贡献,特别是对重核,而对轻核它的贡献减弱,对于同位旋矢量激发的贡献可忽略.几组常用的相对论平均场非线性模型参量,不仅能成功的描述有限核的基态性质,也能很好地描述核的巨共振激发.对于N/Z极端情况下,同位旋矢量巨偶极激发模式存在低能集体激发,它是由于费密面附近弱束缚核子的激发和同位旋混杂效应
关键词:
相对论无规位相近似
核巨共振 相似文献
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用相对论平均场计算了26,28,30,32S和22,24,26,28Si的结合能, 均方根半径, 质子皮厚度, 单粒子能级等. 两套参数TM2和NL-SH的计算结果与实验值比较符合. 用平均场与相对论Eikonal近似结合计算出32S和28Si的形状因子和微分截面的结果, 与实验值也符合得较好. 进一步研究了S和Si的同位素链的基本性质和电子散射, 讨论了电子散射的电荷形状因子对电荷密度变化的敏感性. 电荷形状因子在下一代电子--不稳定原子核对撞机上可以测量, 这将能精确测量不稳定核的电荷半径和电荷密度分布, 本文计算的结果可供未来实验参考. 相似文献
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The results of an investigation of the width of the electron and hole spectral functions in an isotropic electron gas with
the Rashba spin-orbit interaction as a function of the wave vector within the G
0
W
0 approximation are reported. This kind of electron gas is used to simulate two-dimensional systems formed by electrons in
In
x
Ga1 − x
As layers of various heterostructures and by surface electron states on Au(111). It is demonstrated how the width of the spectral
function changes as a result of the spin-orbit interaction and how it depends on the branch index of the energy spectrum split
by this interaction. 相似文献
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V. Milosavljević S. Djeniže 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,15(1):99-104
Characteristics of the Stark broadened and overlapping 447.1 nm He I spectral line and its forbidden 447.0 nm components have
been measured at electron densities between 4.4×1022 m-3 and 8.2×1022 m-3 and electron temperatures between 18 000 K and 33 000 K in plasmas created in five various discharge conditions using the
low pressure pulsed arc as an optically thin plasma source operated in helium-nitrogen-oxygen gas mixture. Good agreement
was found among our measured line characteristics and their existing calculated values, based on the quasistatic approximation.
Possible influence of the singly ionized oxygen impurity atoms (O II) on the intensity values of the dip between allowed and
forbidden components was found that can explain the disagreement among some existing experimental and calculated line characteristics
data, at higher electron temperatures and densities. On the basis of the observed asymmetry of the 447.1 nm spectral line
profile we have obtained the ion contribution parameter at 1022 m-3 electron density and 8 000 K electron temperature.
Received 20 February 2001 and Received in final form 25 April 2001 相似文献
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S. Yu. Glazov A. A. Kovalev N. E. Mescheryakova 《Bulletin of the Russian Academy of Sciences: Physics》2012,76(12):1323-1325
The law of plasma wave dispersion in an electron gas in a superlattice based on graphene on a striped substrate is studied numerically. Calculations are performed based on the quantum theory of plasma waves in the approximation of random phases with allowance for umklapp processes. The estimated plasmon frequencies for the graphene-based superlattices on striped substrates now under theoretical study is ω ≤ 1014 s?1. 相似文献
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A. V. Germanenko G. M. Min’kov O. E. Rut A. A. Sherstobitov 《Bulletin of the Russian Academy of Sciences: Physics》2010,74(1):72-74
The contribution of the electron—electron interaction to the conductivity of the two-dimensional electron gas in an Inx Ga1-x As single quantum well with different disorder strengths was experimentally studied. It is shown that the data are described
well within the framework of the one-loop approximation of the renormalization group theory so long as the conductivity of
the system remains higher than around 15e
2/μh. 相似文献
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The contribution of the virtual process γγ → π+π? is evaluated, first treating the quantum electrodynamics exactly and then using the equivalent photon approximation. The dependence on electron scattering angles, electron energies, ππ invariant mass and γπ momentum transfer is investigated. The approximation is very good if both electron scattering angles are less than 0.1 rad, but is 20%–40% too big (depending on the precise version used) if either angle is integrated over. It is explained that the approximation is not Lorentz invariant; numerical results are given only for beams with anti-parallel momenta. 相似文献
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D. V. Kulakovskii S. I. Gubarev Yu. E. Lozovik 《Journal of Experimental and Theoretical Physics》2002,94(4):785-793
The changes in binding energy and oscillator strength of the exciton state due to the screening by a quasi-two-dimensional electron gas are calculated self-consistently in the approximation of noninteracting electrons and in the local field approximation. It is shown that the collapse of the bound state occurs at very low concentrations, N s≈5×109 cm?2, which is a consequence of the inclusion of the nonlinearity of the response of the system to a Coulomb perturbation. The temperature dependence of the exciton collapse is investigated. The phase diagram of the dissociation of the given bound state is constructed, and the region in which it is possible to observe experimentally the temperature dependence of the exciton collapse is indicated. 相似文献
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O. Moreno P. Sarriguren E. Moya de Guerra J.M. Udias T.W. Donnelly I. Sick 《Nuclear Physics A》2009,828(3-4):306-332
The influence of nuclear isospin mixing on parity-violating elastic electron scattering is studied for the even–even, N=Z nuclei 12C, 24Mg, 28Si, and 32S. Their ground-state wave functions have been obtained using a self-consistent axially-symmetric mean-field approximation with density-dependent effective two-body Skyrme interactions. Some differences from previous shell-model calculations appear for the isovector Coulomb form factors which play a role in determining the parity-violating asymmetry. To gain an understanding of how these differences arise, the results have been expanded in a spherical harmonic oscillator basis. Results are obtained not only within the plane-wave Born approximation, but also using the distorted-wave Born approximation for comparison with potential future experimental studies of parity-violating electron scattering. To this end, for each nucleus the focus is placed on kinematic ranges where the signal (isospin-mixing effects on the parity-violating asymmetry) and the experimental figure-of-merit are maximized. Strangeness contributions to the asymmetry are also briefly discussed, since they and the isospin mixing contributions may play comparable roles for the nuclei being studied at the low momentum transfers of interest in the present work. 相似文献
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The electron distribution function, transport coefficients and rate coefficients for the dissociation of CF4 and the excitation of a1 g and b1
g
+
states of oxygen have been calculated for a CF4 + O2 mixture discharge. The two-term approximation was used in solving the electron Boltzmann equation. The influence of the dissociation was ignored, so that the results are parametric in the density reduced electric fieldE/N and the ratio of the mixture components. Only slight dependence of the calculated quantities on the composition of the gas mixture has been observed. The critical electric field for the onset of the discharge was found to beE/N=1.1–1.25 × 10–15 Vcm2 and it is weakly decreasing with growth of the oxygen content. With a small amount of oxygen added to CF4 the electron distribution function and the mean kinetic energy remain practically unchanged. 相似文献
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M.O. Manasreh Godfrey Gumbs C. Zhang C.E. Stutz K.R. Evans C.A. Bozada I. Lo W.C. Mitchel 《Superlattices and Microstructures》1992,11(4)
The 2-dimensional electron gas (2DEG) in an Al0.6Ga0.4Sb/InAs single quantum well is studied using cyclotron resonance and Shubnikov - de Haas (SdH) techniques. The effective mass (m*) of the 2DEG was obtained from the peak positions of the cyclotron resonance transmission spectra. The results exhibit oscillatory behavior as a function of the magnetic field strength (B). The m* value extracted from the temperature dependence of the SdH oscillations is in good agreement with the average value of m* obtained from cyclotron resonance measurements. The effective mass is calculated as a function of B using an electron self-energy model based on the Hartree-Fock approximation. The calculated m* values also show oscillatory behavior similar to that of the measured cyclotron resonance m*. Both experiment and theory show that m* maxima are shifted from the integral values (both odd and even) of the filling factors. 相似文献
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Changes in the binding energy and oscillator strength of an exciton state due to screening by a quasi-two-dimensional electron gas were calculated self-consistently in a nonlinear approximation. It was shown that the collapse of the bound state proceeds at very small concentrations N s ?5×109 cm?2, which is a consequence of taking into account the nonlinearity of the system response to the Coulomb perturbation. 相似文献