Low-lying non-normal parity states in B-8 measured by proton elastic scattering on Be-7

A new measurement of proton resonance scattering on Be-7 was performed tip to the center-of-mass energy of 6.7 MeV using the low-energy RI beam facility CRIB (CNS Radioactive Ion Beam separator) at the Center for Nuclear Study of the University of Tokyo. The excitation function of Be-7 + p elastic scattering above 3.5 MeV was measured Successfully for the first time, providing important information about the resonance structure of the B-8 nucleus. The resonances are related to the reaction rate of Be-7(p.gamma)B-8. which is the key reaction in solar B-8 neutrino production. Evidence for the presence of two negative parity states is presented. One of them is a 2(-) state observed as a broad s-wave resonance, the existence of which had been questionable. Its possible effects on the determination of the astrophysical S-factor of Be-7(p.gamma)B-8 at solar energy are discussed. The other state had not been observed in previous measurements, and its spin and parity were determined as 1(-). (C) 2009 Elsevier B.V. All rights reserved.

Theoretical calculation of photoionization cross sections of B-like ions: N2+, O3+ and F4+

There can be found some notable discrepancies with regard to the resonance structures when R-matrix calculations from the Opacity Project and other sources are compared with recent absolute experimental measurements of Bizau et al [Astron. Astrophts. 439 387 (2005)] for B-like ions N2+, O3+ and F4+. We performed close-coupling calculations based on the R-matrix formalism for the photoionizations of ions mentioned above both for the ground states and first excited states in the near threshold regions. The present results are compared with experimental ones given by Bizau et al and earlier theoretical ones. Excellent agreement is obtained between our theoretical results and the experimental photoionization cross sections. The present calculations show a significant improvement over the previous theoretical results.

The properties of halo structure for B-17

The total reaction cross section (1724 +/- 93 mb) of B-17 at the energy of 43.7 A MeV on C target has been measured by using the transmission method at the Radioactive Ion Beam Line in Lanzhou (RIBLL). Assuming B-17 consists of a core B-15 plus two halo neutrons, the total cross section of B-17 on C target was calculated with the zero-range Glauber model, where double Gaussian density distributions and Gaussian plus HO density distributions were used. It can fit the experimental data very well. The characteristic of halo structure for B-17 was found with a large diffusion of the neutrons density distribution.

Configuration of the valence neutrons of B-17

The reaction cross section of B-17 on C-12 target at (43.7 +/- 2.4) MeV/u has been measured at the Radioactive Ion Beam Line in Lanzhou (RIBLL). The root-mean-square matter radius (R-rms) was deduced to be (2.92 +/- 0.10) fm, while the R-rms of the core and the valence neutron distribution are 2.28 fm and 5.98 fm respectively. Assuming a "core plus 2n" structure in B-17, the mixed configuration of (2s(1/2)) and (1d(5/2)) of the valence neutrons is studied and the s-wave spectroscopic factor is found to be (80 +/- 21)%.

Study of n=2, Delta n=0 transition of Be-, B-, C-, N- and O-like sequence in the beam-foil spectrum of titanium

The foil-excited the spectrum of highly stripped titanium ions between 12-40 nm has been studied. Titanium ions of 80 and 120 MeV were provided by the HI-13 tandem accelerator at the China Institute of Atomic Energy. GIM-957 XUV-VUV monochromator was refocused to get highly-resolved spectra. Our experimental results and the published spectral data of laser-produced plasma show agreement in nearly all cases within +/- 0.03 nm. The spectra contained some weak or strong lines previously unclassified. These spectral lines mainly belong to 2s2p(2) for TiXVIII, 2p(3) for TiXVIII, 2s2p(3) for TiXVII, 2p(6)4p for Ti XII and 2p(6)3d for Ti XII transitions.

B-(*())(B)over-bar(()*()) intermediate states contribution to Gamma(4S, 5S) -> eta(b) + gamma radiative decay

In this work, we investigate the rescattering effects in the radiative decay Gamma(5S) -> eta(b) + gamma , which were suggested to be crucially important for understanding the anomalous largeness of the branching ratios B(Gamma(5S) -> Gamma(1S) + pi pi) and B(Gamma(5S) -> Gamma(1S) + eta). Our calculations show that the rescattering effects may enhance Gamma(Gamma(10860) -> eta(b) +gamma) by four orders, but the tetraquark structure does not. Recently the BABAR and CLEO collaborations have measured the mass of eta(b) and the branching ratios B(Gamma(2S) -> eta(b) +gamma), B(Gamma(3S) -> eta(b) +gamma). We hope that very soon, Gamma(10860) -> eta(b) + gamma) will be measured and it would be an ideal opportunity for testing whether the rescattering or the tetraquark structure is responsible for the anomaly of B(Gamma(5S) -> Gamma(nS) pi(+) pi(-))(n = 1, 2, 3)), i. e., the future measurements on the radiative decays of Gamma(5S) might be a touchstone of the two mechanisms.

Restudy on the wave functions of Gamma(nS) states in the light-front quark model and the radiative decays of Gamma(nS) -> eta(b) + gamma

The light-front quark model has been applied to calculate the transition matrix elements of heavy hadron decays. However, it is noted that using the traditional wave functions of the light-front quark model given in the literature, the theoretically determined decay constants of the Gamma(nS) obviously contradict the data. This implies that the wave functions must be modified. Keeping the orthogonality among the nS states and fitting their decay constants, we obtain a series of the wave functions for Gamma(nS). Based on these wave functions and by analogy with the hydrogen atom, we suggest a modified analytical form for the Gamma(nS) wave functions. Using the modified wave functions, the obtained decay constants are close to the experimental data. Then we calculate the rates of radiative decays of Gamma(nS) -> eta(b) + gamma. Our predictions are consistent with the experimental data on decays Gamma(3S) -> eta(b) + gamma within the theoretical and experimental errors.

Measurement of the total reaction cross section for the mirror nuclei N-12 and B-12

The mirror nuclei N-12 and B-12 are separated by the Radioactive Ion Beam Line in Lanzhou (RIBLL) at HIRFL from the breakup of 78.6 MeV/u N-14 on a Be target. The total reaction cross-sections of N-12 at 34.9 MeV/u and B-12 at 54.4 MeV/u on a Si target have been measured by using the transmission method. Assuming N-12 consists of a C-11 core plus one halo proton, the excitation function of N-12 and B-12 on a Si target and a C target were calculated with the Glauber model. It can fit the experimental data very well. The characteristic halo structure for N-12 was found with a large diffusion of the protons density distribution.

Two-electron-one-photon M1 and E2 transitions between the states of the 2p(3) and 2s(2)2p odd configurations for B-like ions with 18 <= Z <= 92

Two-electron-one-photon (TEOP) M1 and E2 transition energies, line strengths and transition probabilities between the states of the 2p(3) and 2s(2)2p odd configurations for B-like ions with 18 <= Z <= 92 have been calculated using the GRASP2K package based on the multiconfiguration Dirac-Hartree-Fock (MCDHF) method. Employing active-space techniques to expand the configuration list, we have systematically considered the valence, core-valence and core-core electron correlation effects. Breit interaction and quantum electrodynamical (QED) effects were also included to correct atomic state wavefunctions and the corresponding energies. Influences of electron correlation, Breit interaction and QED effects on transition energies and line strengths of the TEOP M1 and E2 transitions were analysed in detail. The present results were also compared with other theoretical and experimental values.

CONSISTENT THREE-BODY FORCE WITH BONN B POTENTIAL AND NEUTRON STAR STRUCTURE

Microscopic three-nucleon force consistent with the Bonn B two-nucleon potential is constructed, which includes Delta(1232), Roper, and nucleon-antinucleon excitation contributions. Recent results for the choice of the meson parameters are discussed. The forces are used in Brueckner calculations and the saturation properties of nuclear matter are determined. At the high densities,the nuclear equation of state and the symmetry energy are calculated. The corresponding neutron star mass-radius relations are presented.

丰中子新核素238Th的合成、鉴别和230Ac b 延发裂变的观测

新核素的合成及衰变性质的研究一直是核物理科学的前沿领域，它对于人类拓广对原子核运动规律的认识有着十分重要的意义。本文首先概述了新核素合成的意义、方法，并简要阐述了一种奇异的衰变方式—β~-延发裂变，为实验部分的论述提供理论基础。在实验部分，本文阐述了用放射化学方法研究了钍、钡、镭等复杂反应产物的化学分离。通过在Th的分离中引用PMBP萃取和反萃体系，并采用氧化还原体系有效地去除了绝大多数杂质元素，特别是非常好的去除了碘和溴离子的沾污，较好地完成了Th与其它反应产物的分离。对Ba、Ra的分离主要采用快速的阳离子交换流程，达到了满意的分离效果。对用中能~(18)O离子束照射铀、钍的反应产物进行分离，对分离出的钍、钡、镭样品进行了γ（X）单谱和时间序列谱测量。并对记录下来的样品的谱图进行了分析。使用上述方法，我们在兰州重离子加速器（HIRFL）上用~(18)O离子照射重铀酸铵靶，通过多核子转移反应，首次合成并鉴别了新核素不相识~(238)Th。 同时通过不同的反应道产生~(237)Th，并对~(237)Th的半衰期进行了测定；在HIRFL上用~(18)O离子照射氧化钍靶对~(230)Ra的子体~(230)Ac的β~-延发裂变现象进行了观测，在被Ra样品爆光的云母径迹探测器上观察到了两个裂变径迹，从ThO_2靶中用三次BaCl_2沉淀法分离出钡、使用γ谱学这技术测定了十多个Ba的放射性同位素的截面。

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.

奇奇核170Re在束g谱学和176Ir EC/b+衰变研究

本论文在 166MeV 的束流能量下，利用重离子熔合蒸发反应 142 Nd（32 S， 1p3nγ ）170 Re 布居了 170 Re 的高自旋激发态，用 12 套带 BGO反康普顿抑制的高 纯锗探测器阵列进行了在束 X-γ 和γ γ − 符合测量。在 210MeV 的束流能量下， 利用重离子熔合蒸发反应 146 Nd（35 Cl，5nγ ）176 Ir 产生具有 β+ / EC 衰变性质的 核素 176 Ir, 由氦喷嘴快速带传输系统将反应产物送到低本底区，用一台小平面探 测器、一台轴对称型高纯锗探测器和一台 CLOVER 探测器进行了γ γ − 符合和 t γ − 单谱测量。基于这些测量结果，研究了 170 Re 的高自旋态和 176 Ir 的 β+ / EC 衰变性质。 本工作基于γ−γ符合关系及周围邻近核已知信息的综合分析，首次建立了包 括 16 个能级 26 条γ 跃迁的双奇核 170 Re 的转动带能级纲图，并利用推转壳模型、 粒子转子模型等对其进行了分析和讨论。根据实验提取出的准粒子顺排、 Routhian、旋称劈裂等结构信息和邻近双奇核带结构系统学知识的比较分析，指 出该带的两准粒子组态是 11/213/2 hi π ν ⊗ ，并且该带在低自旋出现旋称反转。 基于对 176 Ir 核 β+ / EC衰变实验数据的离线处理分析，对早先发表的 176 Ir 衰 变γ 跃迁进行确认的同时又发现了 4 个新能级和 13 条新的γ 射线，丰富了 176 Os 核的低位激发态能级纲图。根据典型γ 射线的衰变时间谱建议了 176 Ir核的一个长 寿命低自旋同核异能态，同时通过两准粒子耦合的半经验计算建议了其组态。

20Na、23Al、24Si的b＋缓发粒子发射及相关的天体反应率的实验研究

以兰州放射性束流线装置(RIBLL)为依托,利用弹核碎裂机制产生了远离稳定线的核素,通过研究一些放射性核素<'20>Na、<'23>Al、<'24>Si的β<'+>缓发粒子特性,并结合核结构的测量,初步研究了<'16>O(α,γ)<'20>Ne、<'22>Na(p,γ)<'23>Mg以及<'23>Mg(p,γ)<'24>Al反应.实验测量到了β<'+>缓发母核(先驱核)的半衰期,缓发粒子的能谱和相对强度,并根据壳模型计算指定了部分激发能级的自旋,进而得到了它们的相对共振强度以及热核反应率等.通过实验,我们测量了5.627,5.788,6.725MeV等几个<'20>Ne<'*>的低能缓发α粒子能级,得到<'20>Na的其半衰期T<,1/2>=459±7ms,给出了10.584MeV和10.843MeV的两个能级的相对共振强度分别为0.59eV、1.2eV,计算了其直接俘获的贡献和低能共振态对反应率的贡献;对于<'22>Na(p,γ)<'23>Mg反应,我们重点测量了<'23>Mg的靠近<'22>Na+p俘获阈附近的能级,将探测器的探测阈降低到了200KeV左右,并新发现了一条激发能级具有缓发质子的特性,其能量为8.916MeV(衰变质子能量为1.337MeV),为了验证测量结果的准确性,我们进行了第二次测量,结果证实了8.916MeV及9.598MeV能级具有缓发质子特性,其中9.598MeV能级的缓发质子在2000年被K.Perajarvi等发现,并又新测量到了能量为8.990,9.060,9.138,9.374MeV的四个能级也存在缓发质子特性.实验得到<'24>Si的衰变半衰期为104±10ms,第一次测量到<'24>Mg低能的几个衰变质子谱线,它们在天体物理中具有重要的作用.