共查询到20条相似文献,搜索用时 203 毫秒
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利用基于多组态Dirac-Hartree-Fock(MCDHF) 理论方法的相对论原子结构计算程序包GRASP2K, 细致计算了中性锂原子、类锂Be+, C3+, O5+, Ne7+, Ar15+, Fe23+, Mo39+, W71+及U89 + 离子基组态及较低的激发组态1s2nl (n = 2---4, l =s,p,d,f) 的精细结构能级, 以及各能级间发生电偶极(E1) 自发辐射跃迁的能量、概率及振子强度. 同时, 在非相对论极限下, 计算了其相关原子参数. 通过对相对论及非相对论计算结果的比较, 系统研究了相对论效应对类锂等电子系列离子能级结构及E1跃迁性质的影响, 揭示了随原子核电荷数Z变化时, 跃迁能、振子强度强烈依赖于量子数n, l, j变化的规律; 同时, 目前的计算结果与其他已有的理论计算及实验测量结果进行了比较. 相似文献
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本文用扩散型光学位阱对低能(中子2—4兆电子伏,质子3.5—7兆电子伏)非弹性散射角分布、激发函数和γ射线角分布进行了计算,目的是比较系统地定量检验Hauser-Feshbach理论。计算结果和实验符合得很好。说明H.F.理论中的基本出发点,即不同复合核态之间的干涉相消的假设,是近似成立的。在此基础上,我们进一步讨论了可以用H.F.公式来提供光学位阱参数与能级自旋宇称知识的可能性,后者具体应用至N14的高激发态,计算表明:N14的4.91兆电子伏和5.01兆电子伏能级的自旋分别为0和2,能级的自旋对截面的大小影响很显著,但宇称则几乎没有影响。同时我们也应用H.F.理论讨论了相邻奇-偶核和偶-偶核弹性散射的差异。最后,考虑到同位旋在轻核中是一个准守恆量,本文中研究了在复合核过程中同位旋守恆的可能性,给出了考虑同位旋守恆以后的H.F.公式。并对于N14(p,p′)N14*至第一激发态2.31兆电子伏(t=1),和第二激发态3.95兆电子伏(t=0)的非弹性散射角分布,分别在同位旋守恒和不守恒情况下进行了计算,结果表明,不守恒时的计算值和现有的实验非常接近,看来同位旋量子数在轻核的复合核反应中守恆性是很差的。 相似文献
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在相对论平均场理论中引入同位旋标量-矢量介子ω张量项, 以208Pb为例,研究了张量项对原子核平均势场、介子场、自旋-轨道耦合势、单粒子能级的自旋-轨道劈裂和原子核壳层结构等的影响.结果发现张量项对核子平均势的影响主要表现在原子核的表面.随着张量耦合强度的增加, 自旋-轨道耦合势增强,单粒子能级的自旋-轨道劈裂增大,从而导致原子核单粒子能级的壳层结构发生很大变化,传统幻数所对应的主壳消失, 新的主壳出现. 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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M. M. Mirabutalybov 《Russian Physics Journal》2010,53(3):276-295
In the context of nonrelativistic theory in the distorted wave approximation, a three-dimensional form of analytical expression
for the differential cross section of scattering of nucleons with intermediate energies on atomic nuclei is derived. In the
context of this theory, the main parameters of elastic scattering of protons with incident energy of 1 GeV on the 208Pb nucleus are determined. For inelastic scattering of protons with nuclear surface vibrations, giant multipole resonances
in the excited nucleus are investigated for the collective nucleus model. The energy losses of the scattered proton are calculated
together with the energies of giant dipole and quadrupole resonances and nuclear surface vibration energy. This allows the
deformation parameter of the excited nucleus to be calculated. 相似文献
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B. Pålsson J. Krumlinde I. Bergqvist L. Nilsson A. Lindholm D.C. Santry E.D. Earle 《Nuclear Physics A》1980,345(1):221-231
The proton capture cross section for the reaction 176Yb(p, γ)177Lu has been measured for incident proton energies between 6 and 24 MeV. The excitation function for this deformed nucleus agrees remarkably well with the results of previous studies on spherical nuclei, e.g. 142Ce(p, γ)143Pr. The results indicate that the giant dipole resonance (GDR) is strongly excited as predicted by the direct-semidirect (DSD) model. It is found that the model describes reasonably well the excitation function. In the low-energy proton range, where the excitation function increases rapidly with proton energy, the observed cross section is significantly higher than the DSD predictions. The difference can only partly be explained by compound nucleus contributions. In the high-energy end, the predicted cross section tends to be too high primarily due to an increasing contribution of direct capture to orbitals with large angular momenta. 相似文献
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《Nuclear Physics A》1986,452(3):477-492
The theory of deuteron diffraction dissociation is extended to the case of weakly-bound light-ion interaction with diffused-edge nuclei. The formalism developed is applied to the analysis of coincident energy spectra and angular distributions of the 12C,51V,90Zr(3He, pd) reactions at 90 MeV energy. A satisfactory agreement between the theory and experimental data is obtained. Conclusions are drawn about the diffraction character of the 3He ions interaction with nuclei at the energy in question. It is shown that the inclusion of finite-range nuclear forces between clusters in the projectile leads to an increase of the 3He dissociation cross section. The sensitivity of the dissociation cross section to the diffuseness parameter of the nuclear boundary is established. The possibility is also discussed of using the dissociation reaction of weakly-bound light projectiles by composite nuclei for study of the nuclear surface in coincidence measurements at sufficiently high energies. 相似文献
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M. P. Avotina 《Czechoslovak Journal of Physics》1983,33(3):257-265
Conclusion Magnetic moments of almost all nuclei are independent of excitation energy and level parity.Coupled neutrons and protons appear to be grouped into dipoles. The doubly magic208Pb nucleus and the neighbouring ones are found to be most complicated, for calculations, since their level magnetic structure is very unstable.Magnetic moments of all even-even nuclei known up to now may be described uniformly.It is necessary to introduce the effective magnetic moments (g-factors) for both protons and neutrons for a certain nucleus individually but according to uniform approach. These effective values are produced by all nucleons of a nucleus.It is possible to speak about transient properties of nuclei if there is a mutual compensation of the proton and neutron effectiveg-factors.The described method — from the experimental regularities via consideration of separate factors with the help of diagrams over the whole region of nuclei — is very convenient for distinguishing new regularities. 相似文献
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The first microscopic calculation of inelastic reactions on nuclei with mass number A = 6 is presented. In particular, we consider the total photoabsorption cross section of 6He and 6Li. It is shown that the halo nucleus 6He exhibits two types of dipole resonances, the normal giant dipole resonance and a low-energy soft dipole resonance associated with the excitation of the outer neutrons. Comparing our results with available experimental data we note the role of P-wave interaction. Calculations are performed using the Lorentz integral transform (LIT) method and the effective interaction in the hyperspherical harmonics formalism (EIHH). 相似文献
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An analysis of the cross sections for photon absorption by isobar nuclei 14C and 14N in the giant-dipole-resonance region demonstrates a high degree of isospin symmetry for this type of collective excitations in the above nuclei. Giant resonances in A = 14 isobar nuclei are related by a simple rescaling procedure that is based on the fact that, for these nuclei, the isospin remains a good quantum number in the process of dipole excitations of energy up to about 40 MeV. The features of the isospin splitting of the giant resonance in the 14C nucleus are refined. The shape of the cross section for photoabsorption in the 14C nucleus—in particular, a large width of the giant resonance in this nucleus—is exhaustively explained. 相似文献
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A. N. Ermakov B. S. Ishkhanov I. M. Kapitonov I. V. Makarenko V. N. Orlin 《Physics of Atomic Nuclei》2010,73(5):737-745
Experimental data on yields of multiparticle photonuclear reactions (involving the emission of up to seven neutrons from the
nucleus involved) on 197Au, 203,205Tl, and 209Bi nuclei in the region extending from the giant dipole resonance to an energy of 67.7 MeV are presented. These data are compared
with the results of modern theoretical calculations that take into account both the excitation of a giant dipole resonance
(GDR) in a nucleus and the photodisintegration of quasideutrons (QD) in it. By and large, experimental data confirm the results
of theoretical calculations—that is, only upon taking simultaneously into account both alternative photodisintegration mechanisms
(GDR excitation and QD photodisintegration) can one describe these experimental data. The contribution of QD photodisintegration
grows with increasing photon energy and neutron multiplicity and becomes dominant for reactions involving the emission of
not less than five neutrons from the nucleus being considered. The integrated cross sections for the processes in question
were estimated on the basis of simultaneously employing experimental yields of multinucleon photonuclear reactions and the
respective cross-section shapes calculated theoretically. 相似文献