Experimental study of the U-238(S-36,3-5n)(269-271)Hs reaction leading to the observation of (270)Hs

The deformed doubly magic nucleus (270)Hs has so far only been observed as the four-neutron (4n) evaporation residue of the reaction Mg-26+Cm-248, where a maximum cross section of 3 pb was measured. Theoretical studies on the formation of (270)Hs in the 4n evaporation channel of fusion reactions with different entrance channel asymmetry in the framework of a two-parameter Smoluchowski equation predict that the reactions Ca-48+Ra-226 and S-36+U-238 result in higher cross sections due to lower reaction Q values, in contrast to simple arguments based on the reaction asymmetry, which predict opposite trends. Calculations using HIVAP predict cross sections for the reaction S-36+U-238 that are similar to those of the Mg-26+Cm-248 reaction. Here, we report on the first measurement of evaporation residues formed in the complete nuclear fusion reaction S-36+U-238 and the observation of (270)Hs, which is produced in the 4n evaporation channel, with a measured cross section of 0.8(-0.7)(+2.6) pb at 51-MeV excitation energy. The one-event cross-section limits (68% confidence level) for the 3n, 4n, and 5n evaporation channels at 39-MeV excitation energy are 2.9 pb, while the cross-section limits of the 3n and 5n channel at 51 MeV are 1.5 pb. This is significantly lower than the 5n cross section of the Mg-26+Cm-248 reaction at similar excitation energy.

Center of mass energy and system-size dependence of photon production at forward rapidity at RHIC

We present the multiplicity and pseudorapidity distributions of photons produced in Au + Au and Cu + Cu collisions at root(NN)-N-s = 62.4 and 200 GeV. The photons are measured in the region -3.7 < eta < -2.3 using the photon Multiplicity detector in the STAR experiment at RHIC. The number of photons produced per average number of participating nucleon pairs increases with the beam energy and is independent of (lie collision centrality. For collisions with similar average numbers of participating nucleons the photon multiplicities are observed to be similar for An + Au and Cu + Cu collisions at a given beam energy. The ratios of the number of charged particles to photons in the measured pseudorapidity range are found to be 1.4 +/- 0.1 and 1.2 +/- 0.1 for root(NN)-N-s = 62.4 and 200 GeV, respectively. The energy dependence of this ratio could reflect varying contributions from baryons to charged particles, while mesons are the dominant contributors to photon production in the given kinematic region. The photon pseudorapidity distributions normalized by average number of participating nucleon pairs, when plotted as a function of eta-Y-beam, are found to follow a longitudinal scaling independent of centrality and colliding ion species at both beam energies. (C) 2009 Elsevier B.V. All rights reserved.

Properties of the beta-delayed proton decay of Ho-146

The proton-rich isotope Ho-148 was produced via the fusion-evaporation reaction Mo-92 (Ni-58, 3p1n). The beta-delayed proton decay of Ho-146 was studied by proton-gamma coincidence measurements using a He-jet tape transport system. The gamma-transitions in Tb-145 following the proton emissions were observed, and the beta-delayed proton branching ratios to the final states in the grand-daughter nucleus Tb-145 were determined. According to the relative branching ratios, the ground-state spin of Ho-146 has been proposed and the possible configuration discussed.

Concise methods for proton radioactivity

Concise methods are proposed to study proton radioactivity. The spectroscopic factor is obtained from relativistic mean field (RMF) theory combined with the BCS method (RMF+BCS). The assault frequency is estimated by a quantum mechanical method considering the structure of the parent nucleus. The penetrability is calculated by the WKB approximation. No additional parameters are introduced. The extracted experimental spectroscopic factors are compared with those from the calculations by the RMF+BCS, and the agreement is good, implying that the present methods work quite well for proton radioactivity. Predictions are provided for some most possible proton emissions, which may be useful for future experiments.

Elastic Scattering of He-6 + p at 82.3 MeV/nucleon

Differential cross sections for the elastic scattering of halo nucleus He-6 on proton target were measured at 82.3 MeV/u. The experimental results are well reproduced by optical model calculations using global potential KD02 with a reduction of the depth of real volume part by a factor of 0.7. A systematic analysis shows that this behavior might be related to the weakly bound property of unstable nuclei.

A New High-Spin Level Scheme of I-128

High-spin states in the odd-odd nucleus I-128 are investigated via the Sn-124(Li-7,3n)I-128 reaction at 28 and 32 MeV beam energies. A new level scheme of I-128 is established up to high-spin states at I-pi = 16, including 48 levels and 72 gamma transitions. The present level scheme is largely different from the one in a recent publication due to identification of several doublet and triplet gamma transitions and their proper placements in the level scheme. The high-spin level structure exhibits no obvious collective properties and is possibly associated with two and multi-quasiparticle configurations.

Properties of the beta-Delayed Proton Decay of Er-147

The beta-delayed proton decay of Er-147 is studied experimentally using the Ni-58+Mo-92 reaction at a beam energy of 383 MeV. Based on a He-jet apparatus coupled with a tape transport system, the beta-delayed proton radioactivities both from the nu s(1/2) ground state and the nu h(11/2) isomer in Er-147 are identified by proton-gamma coincidence measurements. By analyzing the time distribution of the 4(+) -> 2(+) gamma transition in the grand-daughter nucleus Dy-146, a half-life of 1.6 +/- 0.2 s is determined for the nu h(11/2) isomer in Er-147. The half-life for the ground state of Er-147 is estimated to be 3.2 +/- 1.2 s.

双奇核188Tl高自旋态能级结构研究

本论文首先介绍了在束谱学实验技术研究原子核高自旋态的基础理论知识，然后描述了实验数据的处理方法。在此基础上，详细分析并讨论了188Tl核高自旋态能级结构的性质。利用能量为170 MeV 的35Cl束流,通过157Gd(35Cl,4n)熔合蒸发反应研了188Tl的高自旋态能级结构。基于实验结果，建立了188Tl基于质子h9/2

187Pt的高自旋态能级结构研究

利用在束γ谱学技术和 173Yb(18O, 4n) 熔合蒸发反应研究了 187Pt 的高自旋态能级结构。在 78 和 85 MeV 束流能量下进行了X-γ-t和γ-γ-t符合测量。实验观测到基于νi13/2，ν7/2−[503]，νi213/2νj, ν3/2−[512] 和ν1/2−[521] 组态的转动带，并且利用推转壳模型(CSM) 和总Routhian面(TRS) 模型对这些转动带的带交叉，形状共存等性质进行了解释。总Routhian面(TRS)计算表明νi13/2转动带具有显著的负γ形变；负宇称带具有近似长椭球的形变。通过比较带内B(M1)/B(E2)比率的实验值和由 Dönau 和 Frauendorf 的半经典公式得到的理论值，发现ν7/2−[503] 转动带在低转动频率下的带交叉是由一对 h9/2 质子顺排引起的

230Ac的 b 延发裂变的观测及新核素合成

第一部分：β延发裂变（βDF）是一种稀有的核衰变模式,它在天体物理学和研究中具有重要价值;为研究远离β稳定线核素提供了可能性,是研究新核素合成的新台阶.第二部分：采用放射化学分离法从中能<'18>O离子辐照过的天然铀靶以及钍靶中分离出放射性Ba同位素,用高分辨的HPGe探测器测量Ba部分的γ射线谱,对测得的时间累计谱进行分析,用常规的计算产额生成截面的方法得到了Ba同位素的生成截面,并对其中的一些截面数据进行了讨论.第三部分：在中子发生器上用14-15MeV的中子轰击天然白金箔,通过<'198>Pt(n,2p）反应产生<'197>Os.使用两台HPGe探测器做γ（X）单谱和X-γ-t符合测量.对测得的数据进行了分析,结果显示我们合成并鉴定了新丰中子同位素<'197>Os,确定它的半衰期为2.8±0.5min.第四部分：用<'133>Ba作示踪剂对Ba在不锈钢片上的分子镀进行了研究.对在异丙醇溶液中的影响Ba分子镀的因素：电镀时间和电流密度等做了条件实验.在电流密度为4.0～6.0mA/cm<'2>,沉积时间30min的实验条件下,可在不锈钢片上获得厚度为0.5～1.0mg/cm<'2>的Ba镀层,也确定了Ba的电镀效率.

基于ImIQMD模型对准裂变和核子集团的研究

本文基于改进的同位旋相关的量子分子动力学(ImIQMD)[1]模型对于反应系统48Ca+208Pb准裂变机制进行了研究。通过计算俘获截面、准裂变碎片质量分布等，并与实验结果进行了比较，我们认为ImIQMD模型对低能重系统准裂变反应的描述基本是合理的。 并合模型是判定碎片的经典模型，但是应用这个模型来判定核子集团会遇到一些困难，因为碎片之间往往相互离得较远，而核子集团之间相互距离相比之下很近。本文第四章对此给出了详细的讨论，提出了对原算法的改进，以及新的算法。 微观动力学模型的发展使得我们可以更细致地了解物理过程之中核子的运动，但是对于重系统而言，直接在核子尺度上来讨论具体的物理问题是十分繁杂的，因为不但核子数众多，而且核子间还存在强烈的相互作用。在这种情况下，根据研究需要定义核子集团的判定标准，而后得到核子集团分布，不但可以使“新的组成”数目减少，而且相互之间的作用强度也会下降，这就降低了处理的繁杂程度，并且与实验现象可以更接近。本文在第四章之中基于这个思想讨论了一些问题

双奇核188Tl高自旋态能级结构研究

本论文首先介绍了在束谱学实验技术研究原子核高自旋态的基础理论知识，然后描述了实验数据的处理方法。在此基础上，详细分析并讨论了188Tl核高自旋态能级结构的性质。利用能量为170 MeV 的35Cl束流,通过157Gd(35Cl,4n)熔合蒸发反应研了188Tl的高自旋态能级结构。基于实验结果，建立了188Tl基于质子h9/2

187Pt的高自旋态能级结构研究

利用在束γ谱学技术和 173Yb(18O, 4n) 熔合蒸发反应研究了 187Pt 的高自旋态能级结构。在 78 和 85 MeV 束流能量下进行了X-γ-t和γ-γ-t符合测量。实验观测到基于νi13/2，ν7/2−[503]，νi213/2νj, ν3/2−[512] 和ν1/2−[521] 组态的转动带，并且利用推转壳模型(CSM) 和总Routhian面(TRS) 模型对这些转动带的带交叉，形状共存等性质进行了解释。总Routhian面(TRS)计算表明νi13/2转动带具有显著的负γ形变；负宇称带具有近似长椭球的形变。通过比较带内B(M1)/B(E2)比率的实验值和由 Dönau 和 Frauendorf 的半经典公式得到的理论值，发现ν7/2−[503] 转动带在低转动频率下的带交叉是由一对 h9/2 质子顺排引起的

球形核139Ce和过渡区核189Pt高自旋态能级结构研究

本论文主要包括以下两部分： 利用能量为50 MeV的 12 C 束流，通过反应 130 Te( 12 C,3n)产生了 139 Ce 的高自旋态。 基于标准在束核谱学实验方法，利用由14套BGO（AC）HPGe 探测器组成的探测器阵 列，进行了X- γ -t和 γ - γ -t符合测量，更新并扩展了 139 Ce 的高自旋能级纲图。139 Ce 的能级结构具有球形原子核的典型特征，其高自旋态是由单粒子激发形成的。本文利用 经验壳模型计算了 139 Ce 的多准粒子激发态能量，研究了其高自旋激发态的多准粒子特 性。 利用能量为88和95 MeV的 18 O 束流，通过重离子熔合蒸发反应 176 Yb( 18 O,5n)，布 居了 189 Pt 的高自旋激发态。实验采用 GEMINI γ射线探测器阵列，进行了X- γ -t 和 γ - γ -t 符合测量。基于γ - γ符合关系、γ射线相对强度、强度平衡原理和交叉跃迁等 信息，建立了新的 189 Pt 高自旋态能级纲图。实验观测到基于 1 13/2 i υ − ， 5/23/2 () f p υ 和 2 13/25/23/2 () ifp υυ − 组态的转动带以及多准粒子激发能级。其中， 1 13/2 i υ − 带的优惠和非优惠旋 称分支分别被扩展到 49/2+ 和31/2+ 能级。本工作利用三轴粒子-转子模型分析了基于 1 13/2 i υ − ， 5/23/2 () f p υ 组态的转动带性质，分析了它们波函数的主要成分，并建议它们分别 具有三轴形变和长椭形变。实验上发现结构非常相近的两个能级序列，我们建议它们具 有 2 13/25/23/2 () ifp υυ − 组态。第一次利用粒子-转子模型计算了这个基于三准粒子组态的转动 带能级能量，很好地再现了实验结果，并建议此带具有扁椭形变。由于与这个组态相应 的 Nilsson 轨道量子数显示了赝自旋量子数特征，我们建议此三准粒子组态转动带为赝 自旋伙伴带。