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通过用QMD模型研究晕核^11Be ^208Pb的近垒熔合反应,发现晕核引起的熔合反应中,并存着两种相互竞争的机制:一方面当入射晕核^11Be靠近靶核时,由于^11Be是弱束缚体系,与靶核的相互作用可使其很容易破裂或少数核子被靶核俘获形成核子转移反应,从而对于熔合表现出压制;另一方面当^11Be的少数中子进入靶核并与靶核相互作用而使得靶核有些激发,而使局部半径增大,导致熔合势垒降低,熔合截面增强。用QMD模型计算出的熔合截面与实验值基本符合,垒附近表现出增强效应。 相似文献
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通过用QMD模型研究晕核11Be+208Pb的近垒熔合反应,发现晕核引起的熔合反应中,并存着两种相互竞争的机制:一方面当入射晕核11Be靠近靶核时,由于11Be是弱束缚体系,与靶核的相互作用可使其很容易破裂或少数核子被靶核俘获形成核子转移反应,从而对于熔合表现出压制;另一方面当11Be的少数中子进入靶核并与靶核相互作用而使得靶核有些激发,而使局部半径增大,导致熔合势垒降低,熔合截面增强.用QMD模型计算出的熔合截面与实验值基本符合,垒附近表现出增强效应. 相似文献
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在双核系统框架下,通过数值法解主方程计算了双核间的核子跃迁全熔合几率.两碰撞核内部激发能由相对运动能损提供,因此能够将核子转移过程与相对运动耦合起来.对一些以Pb为靶的形成超重核的冷熔合反应,计算了最佳激发能、形成双核系统的俘获截面、复合核形成几率及存活几率等,所得到的形成超重核蒸发剩余截面与已知实验值符合较好. In the concept of Dinuclear system (DNS) the complete fusion probability of two touch nuclei via nucleon transfer is described by numerically solving the Master equation. The excitation energy of two colliding nuclei is supplied by the energy dissipation of their relative motion, thus the nucleon transfer process and the relative motion are coupled. For Pb based cold fusion reactions to form super heavy nuclei, the optimal excitation energy, the capture cross section to form a DNS ... 相似文献
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本文系统分析了α粒子与不同的靶核熔合时, 势垒高度和位置与相互作用核的电荷数和均方根半径的关系. 通过基于密度依赖的核子-核子相互作用(CDM3Y6)的双折叠模型来计算核势. 得到了当弹核为α时垒高度和位置的参数化公式. 通过分析质量数从16到238的原子核表明, 参数化公式可以精确地再现弹核为α的熔合反应的垒高度和位置, 其精确度在±1%以内. 此外, 其结果还能很好地和实验值, 经验值, Royer, KNS, AW和亲近势的结果相符合. 相似文献
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We have derived a formula for the neutron radiative capture cross section in the framework of a statistical model approach to nuclear reactions. Based on this formula, new systematics are established between the (n, γ) reaction cross section and the energy level density of a compound nucleus or a relative neutron excess of an even-even target nucleus for neutron incident energy above the resonance region to MeV. Good agreement with experimental data suggests that this new systematical law is helpful to analyze the experimental data. 相似文献
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This paper reports that the experimental excitation functions of reaction (p,n) are measured for ^106pd and ^110pd at proton energy Ep = 6.1 - 7.5 MeV and Ep = 6.0 - 7.7 MeV respectively. The off-resonance excitation functions were compared with calculation values of the statistical model. A new formula used to estimate the peak cross section of isobaric analogue resonance was tested and it was found that calculation values agree reasonably well with the present data within experimental error, which confirms that the excitation strength of isobaric analogue state in (p,n) reaction not only depends on its spin, but also proportionally increases with the projectile proton spatial transmission Tp and the spectroscopic factor S for reaction (d,p) on the same target. 相似文献
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本文研究了关於电子激发原子核的理论。对当原子核由於各多极核矩和电子的电磁相互作用而引起的激发截面进行了一些估计,并且导出表示电子和X射线对原子核激发现象相互关系的公式。这公式仅是原子核能级跃迁中的能量、角动量、和宇称的函数,而不因其他原子核性质而变。把理论的结果和激发In115的试验测量作了一些比较。不过因为缺乏充分的实验测量数据,没能从这比较上得到肯定的结论。於是建议了一些可能进行的研究原子核能级的试验方法。 相似文献
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Multinucleon transfer reactions induced with Ar ions and involving the capture of six charges by the target have been studied. The targets were all the separated isotopes of Nd, and the observed nuclei were 149gTb, 150Dy, 151Dy. The experimental technique involved the measurement of the cross sections, angular distributions, and recoil range at each recoil angle, of the heavy residual nuclei. After transformation of the data into the c.m. system, the angular distributions appear to be peaked backwards, close to 180°. This observation suggests that the present reactions are of the same type as the multinucleon transfer reactions studied by other authors for which the angular distribution of the light fragment was peaked forward in the c.m. system. The energy distributions in the c.m. system were used to check the feasibility of various mechanisms which could lead to the production of the observed isotopes. Each mechanism was supposed to be a two-step process: the first step was the exchange, from the projectile to the target, of a number n of nucléons, leading to an excited intermediate nucleus, and the second step the deexcitation of the intermediate nucleus by nuclear evaporation. This analysis indicates that the most probable mechanisms correspond to n close to 12 (6 protons and 6 neutrons), and to an excitation energy of about 60 MeV for the intermediate nucleus. The distribution of cross sections versus the number of nucléons gained by the target is also in accord with this reaction model. 相似文献
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INFLUENCE OF THE NEUTRON NUMBER OF TARGET NUCLEUS ON CROSS SECTIONS OF PARTICLES EMISSION IN 12C+112,124Sn
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The energy spectra and angular distributions of Li, Be, B particles emitted from the 12C+112Sn and 12C+124Sn reactions at EL=70.0MeV are measured. The angular distributions of the Li, Be, and B particles are found to be peaked around the grazing angle, without any forward peaked component.
The experimental results also showed that the cross section for emission is larger in 12C+112Sn reaction than that in 12C+124Sn reaction, in contrast with the cross sections for Li, Be and B emissions. The indicates the effect of the neutron number of the target nucleus on the emission probability. 相似文献
The experimental results also showed that the cross section for emission is larger in 12C+112Sn reaction than that in 12C+124Sn reaction, in contrast with the cross sections for Li, Be and B emissions. The indicates the effect of the neutron number of the target nucleus on the emission probability. 相似文献
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The neutron capture reaction on a neutron-rich near closed-shell nucleus 82Ge may play an important role in the r-process following the fallout from nuclear statistical equilibrium in core-collapse supernovae.By carrying out a DWBA analysis for the experimental angular distribution of 82Ge(d, p)83Ge reaction we obtain the single particle spectroscopic factors, S2,5/2 and S0,1/2 for the ground and first excited states of 83Ge=82Ge(⊕)n, respectively. And then these spectroscopic factors are used to calculate the direct capture cross sections for the 82Ge(n, γ)83Ge reaction at energies of astrophysical interest. The optical potential for neutron scattering on unstable nucleus 82Ge is not known experimentally. We employed a real folding potential which was calculated by using the proper 82Ge density distribution and an effective nucleon-nucleon force DDM3Y.The neutron capture reactions on neutron-rich closed-shell nuclei are expected to be dominated by the direct capture to bound states. We will show that the direct capture rates on these nuclei are sensitive to the structure of the low-lying states. 相似文献
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Aguilera EF Amador-Valenzuela P Martinez-Quiroz E Lizcano D Rosales P García-Martínez H Gómez-Camacho A Kolata JJ Roberts A Lamm LO Rogachev G Guimarães V Becchetti FD Villano A Ojaruega M Febbraro M Chen Y Jiang H DeYoung PA Peaslee GF Guess C Khadka U Brown J Hinnefeld JD Acosta L Rossi ES Huiza JF Belyaeva TL 《Physical review letters》2011,107(9):092701
Fusion cross sections were measured for the exotic proton-halo nucleus ?B incident on a ??Ni target at several energies near the Coulomb barrier. This is the first experiment to report on the fusion of a proton-halo nucleus. The resulting excitation function shows a striking enhancement with respect to expectations for normal projectiles. Evidence is presented that the sum of the fusion and breakup yields saturates the total reaction cross section. 相似文献
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We present the angular distribution of inelastic intensities corresponding to the excitation of the vibrational modes of CO chemisorbed on Pt(111). The experimental values are compared with those predicted by dipole scattering. All the vibrational modes, including the C-metal, stretch, show experimental values larger than theoretical ones. The difference is attributed to vibrational excitation by impact scattering. The impact scattering cross section is found to be energy dependent and increases for low primary energies (2 eV). The differential cross section is, however, smaller than that observed for resonant scattering in free CO. 相似文献