共查询到20条相似文献,搜索用时 15 毫秒
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A new method is proposed for setting a lower or upper limit a α
n
* on the neutron electric polarizability α
an
. It is based on the fact that the real part of the s-wave scattering amplitude changes sign near the s-wave neutron resonance at E=E*. The methods consist of the observation of the energy behavior of the forward-backward scattering asymmetry ω
1 which experiences a jump at E=E*. If the jump is such that dω
1/dE>0, then α
n
>α
n
*, while if dω
1/dE<0, then α
n
<α
n
*, and if dω
1/dE∼0, then α
n
∼α
n
*. Seven even-even nuclei are found with α
n
* from 0.5 to 3.1 in 10−3 fm3. Some details of a possible experiment with 182W are described.
Pis’ma Zh. éksp. Teor. Fiz. 70, No. 3, 171–174 (10 August 1999)
Published in English in the original Russian journal. Edited by Steve Torstveit. 相似文献
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《Physics letters. [Part B]》1986,171(4):331-334
Starting from a simple hydrodynamical hamiltonian, an analytical expression is derived for the nuclear electric polarizability. The comparison with more detailed calculations is very satisfactory. 相似文献
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Excited states of the nucleon are described as RPA configurations on a mean-field ground state taken from the MIT bag model. A residual interaction of a structure as in the Nambu-Jona-Lasinio model is used. The particlehole states are coupled to good total angular momentum and isospin. Valence excitations of particle-hole type and quark-antiquark (q $\bar q$ ) states from the Dirac-sea are included. The dependence of the baryon spectrum and multipole response functions on the coupling constantG is studied. At critical values ofG the 3q-ground state becomes degenerate with strongly collectiveq99-2 modes. The model is used to calculate the averaged electric polarizability of the neutron and the protonα. Without residual interactionα=7·10?4 fm 3 is found. With residual interaction the value increases toα=(?11)·10?4 fm 3. The measured value ofα is reproduced within experimental error bars. 相似文献
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A. Miffre M. Jacquey M. Büchner G. Trénec J. Vigué 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2006,38(2):353-365
Using an atom interferometer, we have measured the static electric
polarizability of 7Li α=(24.33 ±0.16)×10-30
m3 = 164.2±1.1 atomic units with a 0.66% uncertainty. Our experiment, which is similar to an experiment done on sodium in 1995
by Pritchard and co-workers, consists in
applying an electric field on one of the two interfering beams and measuring the resulting phase-shift. With respect to Pritchard's
experiment, we have made several improvements which
are described in detail in this paper: the capacitor design is such that the electric field can be calculated analytically;
the phase sensitivity of our interferometer is substantially better,
near 16 mrad/
; finally our interferometer is species selective so that impurities present in our atomic beam (other alkali atoms or lithium
dimers) do not perturb our
measurement. The extreme sensitivity of atom interferometry is well illustrated by our experiment: our measurement amounts
to measuring a slight increase Δv of the atom velocity v
when it enters the electric field region and our present sensitivity is sufficient to detect a variation Δv/v ≈6 ×10-13. 相似文献
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The widely used relation alpha; = alpha(0)+Deltaalpha for the electric polarizability, where Deltaalpha is proportional to the r.m.s. charge radius of the system, is revisited within a simple model of two spinless particles bound electromagnetically. A complete set of the relativistic corrections to alpha(0) following from the Breit Hamiltonian is obtained. It is shown that these corrections modify the result for alpha; in comparison to that obtained with alpha(0) taken in the nonrelativistic approximation. We propose that the same situation can take place in the more complicated case of hadrons. Special attention is devoted to the correct definition of the center-of-mass coordinates which are found to be very important. 相似文献
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We consider mesoscopic fluctuations of the dipole moment and the electric polarizability of a disordered thin film in the diffusive regime. It is shown, that the requirement of a fixed particle number is crucial for obtaining finite fluctuations at low temperatures. For systems with sufficient disorder and a long screening length a spontaneous dipole moment should be observable with an atomic force microscope.Dedicated to Prof. H. Wagner on the occasion of his 60th birthday 相似文献
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The σ?2 photonuclear sum rule together with recently determined magnetic susceptibilities is used to evaluate the corrections to the static electric dipole polarizability of nuclei. Those corrections are sizeable in the realm of very light nuclei. 相似文献
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The thermal expansion coefficients of Na(N) clusters with 8=N=40, and Al7, Al-13, and Al-14 clusters are obtained from ab initio Born-Oppenheimer local-density-approximation molecular dynamics. Thermal expansion of small metal clusters is considerably larger than that in the bulk and is size dependent. We demonstrate that the average static electric dipole polarizability of Na clusters depends linearly on the mean interatomic distance and only to a minor extent on the detailed ionic configuration when the overall shape of the electron density is enforced by electronic shell effects. Taking thermal expansion into account brings theoretical and experimental polarizabilities into quantitative agreement. 相似文献
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将高功率脉冲激光作用于金属元靶,探测激光诱导等离子体在靶上产生的电学信号.研究了作用激光能量的差异对等离子体电信号的影响,实验结果表明随着激光能量的增加电信号脉冲幅度逐渐增大并趋于饱和.同时,将激光烧蚀过程中的靶材等效为瞬态电流源,初步建立了激光诱导等离子体等效电路模型,并将该模型应用于激光烧蚀金属靶,对靶上电信号的产生机制进行了详细讨论. 相似文献
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The neutron electric form factor GE,n has been measured at three different four-momentum transfer in a D(|e|→, e′|e|→)p experiment. Neutronwere detected in a recoil 0 polarimeter, using a spin precession method. We present the experiment and the status of data analysis. 相似文献
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A. Ya. Silenko 《Bulletin of the Russian Academy of Sciences: Physics》2007,71(9):1339-1343
When an electric field of resonant frequency acts on a deuteron beam in a storage ring, the tensor electric polarizability stimulates buildup of the vertical polarization of the beam (the Baryshevsky effect). This effect allows high-precision measurement of the tensor electric polarizability of the deuteron, which contains important information about spin-dependent nuclear forces. The general formulas describing the Baryshevsky effect are derived. It is shown that doubling of the resonant frequency leads to dramatic enhancement of the effect. 相似文献
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We present a state-of-the-art evaluation of the polarizability corrections--the inelastic nucleon corrections--to the hydrogen ground-state hyperfine splitting using analytic fits to the most recent data. We find a value Delta(pol)=1.3+/-0.3 ppm. This is 1-2 ppm smaller than the value of Delta(pol) deduced using hyperfine splitting data and elastic nucleon corrections obtained from modern form factor fits. 相似文献