beta(+)/EC decay and systematic analysis of Ir-176,Ir-178

The gamma rays following the beta(+)/EC decay of Ir-176,Ir-178 nuclei have been investigated using in-beam gamma-ray experiment. In addition, with the aid of a helium-jet recoil fast tape transport system, the beta(+)/EC decay of Ir-176 was further studied, the new gamma rays were proved and a low-spin isomer was proposed in Ir-176. The isomeric state was analysized according to the systematics in neighboring nuclei.

beta(+)/EC-decay study of Ir-176 neutron-deficient isotope

The beta(+)/EC decay of doubly odd Ir-176 has been investigated using Nd-146(Cl-35, 5n gamma)Ir-176 heavy ion fusion evaporation reaction at 210MeV bombarding energy. With the aid of a helium-jet recoil fast tape transport system, the reaction products were transported to a low-background location for measurements. Based on the data analysis, the previously published gamma rays in Ir-176 decay were proved, moreover, 3 new levels and 10 new gamma rays were assigned to Ir-176 decay. The new level scheme of Os-176 with low excitation energy has been established. The time spectra of typical gamma rays clearly indicate a long-lived low-spin isomer in Ir-176 nuclide.

Multi-electron processes in C-13(6+) ions with neon collisions in energy region 4.15-11.08 keV/u

The cross-section ratios of double-, triple-, quadruple-, and the total multi-electron processes to the single electron capture process sigma(DE)/sigma(SC), sigma(TE)/sigma(SC), sigma(QE)/sigma(SC) and sigma(ME)/sigma(SC)) as well as the relative ratios among reaction channels in double-electron active, triple-electron active and quadruple- electron active are measured in C-13(6+) -Ne collision in the energy region of 4.15-11.08 keV/u by employing position-sensitive and time-of-flight coincident techniques. It is determined that the cross-section ratios sigma(DE)/sigma(SC), sigma(TE)/sigma(SC), sigma(QE)/sigma(SC) and sigma(ME)/sigma(SC) are approximately the constants of 0.20 +/- 0.03, 0.16 +/- 0.04, 0.06 +/- 0.02 and 0.42 +/- 0.05. These values are obviously smaller than the predictions of the molecular Coulomb over-the-barrier model (MCBM) [J. Phys. B 23 (1990) 4293], the extended classical over-the-barrier model (ECBM) [J. Phys. B 19 (1986) 2925] and the semiempirical scaling laws (SL) [Phys. Rev. A 54 (1996) 4127]. However, the relative ratios among partial processes of DE, TE and QE are found to depend on collision energy, which suggests that the collision dynamics depends on the collision velocity. The limitation of velocity-independent character of ECBM, MCBM and SL is undoubtedly shown.

Experimental investigation of transfer ionization mechanism in slow He2+ -He collisions

The processes of transfer ionization in He2+ -He collisions at energies ranging from 20 to 40 keV have been studied experimentally by means of cold target recoil ions momentum spectroscopy. From the longitudinal momentum spectra of recoil ions, different mechanisms of transfer ionization have been obtained. The results show that one of the electrons of helium atom being captured into the ground state of projectile ion He2+ and the other one emitted to the continuum state of projectile or target are the dominant mechanisms of transfer ionization. The autoionization cross section of projectile after two-electron capture into a double excited state is small. Transfer ionization for one target electron capture into ground state and the other one into the continuum of projectile mainly occurs at large impact parameter collisions.

Isospin-dependent pairing interaction from nuclear matter calculations

The isospin dependence of the effective pairing interaction is discussed on the basis of the Bardeen, Cooper, and Schrieffer theory of superfluid asymmetric nuclear matter. It is shown that the energy gap, calculated within the mean field approximation in the range from symmetric nuclear matter to pure neutron matter, is not linearly dependent on the symmetry parameter owing to the nonlinear structure of the gap equation. Moreover, the construction of a zero-range effective pairing interaction compatible with the neutron and proton gaps in homogeneous matter is investigated, along with some recent proposals of isospin dependence tested on the nuclear data table.

Evidence of strong projectile-target-core interaction in single ionization of neon by electron impact

The momentum distributions of recoil ions were measured in the single ionization of neon by electron impact at incident energies between 80 and 2300 eV. It was found that there are a noticeable number of recoil ions carrying large momenta, and the relative contributions of these ions becomes more pronounced with the further decrease of incident electron energy. These observed behaviors indicate that there is a strong projectile-target-core interaction in the single-ionization reaction. By comparing our results with those of electron-neon elastic scattering, we concluded that the elastic scattering of the projectile electron on the target core plays an important role at low and intermediate collision energies.

Atomic Structures and Radiative Properties of He-like Ions in Debye Plasmas

A detailed investigation of plasma screening effects on atomic structure and transition properties are presented for He-like ions embedded in dense plasma environment. Multi-configuration Dirac-Fock calculations were carried out for these ions by considering a Debye-Huckel potential. A large-scale relativistic configuration-interaction method is adopted to calculate transition energies and transition probabilities and to allow for a systematic improvement of the calculations. Comparison of the presently calculated results with others, when available, is made.

2.6 s isomer of Nd-129

Nd-129 was produced by irradiation of an enriched target of Ru-96 with a Ar-36 beam and studied by using a helium-jet fast tape transport system in combination with X-gamma and gamma-gamma coincidence measurements. A 2.6s isomer of Nd-129 was observed for the first time and tentatively proposed to be the configuration of 1/2[411].

Influence of core property on multi-electron process in slow collisions of isocharged sequence ions with neon

Influence of core property on multi-electron process in the collisions of q = 6-9 and 11 isocharged sequence ions with Ne is investigated in the keV/u region The cross-section ratios of double-, triple-, quadruple- and total multi-electron processes to the single electron capture process as well as the partial ratios of different reaction channels to the relevant multi-electron process are measured by using position-sensitive and time-of-flight techniques The experimental data are compared with the theoretical predictions including the extended classical over-barrier model, the molecular Columbic barrier model and the semi-empirical scaling law Results show a core effect on multi-electron process of isocharge ions colliding with Neon, which is consistent with the results of Helium we obtained previously

Observation of a Possible New Isomer in Ir-175

The neutron deficient nuclide Ir-175 was produced by irradiation of Nd-146 with 210 MeV Cl-35 via a fusion-evaporation reaction channel. The reaction products were transported to a low-background location using a helium-jet recoil fast-moving tape-transport system for measurement. The experimental devices and data analysis method are introduced. Based on the decay-curve fitting of the beta-delayed gamma ray from Ir-175, realized by the least-square method, a new long-lived isomeric state of Ir-175 is proposed and briefly discussed.

The effect of hyperfine interaction on the lifetime of the 3s3p P-3(2) level of Mg-like ions

On the basis of previous work, the hyperfine-induced 3s3p P-3(2) -> 3s(2) S-1(0) E1 transition probabilities of Mg-like ions were further calculated using the GRASP2K package based on the multiconfiguration Dirac-Hartree-Fock method. The contribution to the lifetime of the P-3(2) level from the 3s3p P-3(2) -> 3s(2) S-1(0) hyperfine-induced E1, 3s3p P-3(2) -> 3s3p P-3(1) M1, 3s3p P-3(2) -> 3s(2) S-1(0) M2 and 3s3p P-3(2) -> 3s3p P-3(0,1) E2 transition was discussed in detail. It was found that hyperfine interaction has an obvious effect on the lifetime at the beginning of the Mg-like isoelectronic sequence.

A 3 Tesla Superconducting Magnet for Hall Sensor Calibration

A 3 T superconducting magnet with a 70 mm diameter warm bore and energy storage of 47 kJ has been successfully fabricated and tested, which can be used to calibrate Hall sensors in high magnetic field as well as conduct superconducting experiments. The magnet consists of three solenoid coils and an iron yoke. The homogeneity of the magnetic field in the region of interest (ROI) is +/- 6.0 x 10(-5). The coils of the magnet were fabricated with NbTi-Cu superconducting wire and the stray magnetic field is shielded by an iron yoke. The coils and yoke are fully immersed in a helium vessel. The optimized structural design, stress and quench simulation, fabrication and test results are presented in this paper.

电子入射氦原子的双电离的实验研究

反应显微成像谱仪能够在全空间范围内探测碰撞反应后全部荷电出射粒子的动量信息，本论文基于适用于低能电子入射原子的双电离或多重电离的反应显微成像谱仪，对电子入射氦原子的双电离反应机制进行了实验研究。论文着重对适用于低能电子入射原子的双电离的反应显微成像谱仪及其特性进行介绍，并介绍和讨论了目前几种计算原子的双电离微分截面的理论模型。通过对106eV电子入射氦原子的双电离实验结果进行分析讨论，获得了以下结果：1，反应后出射电子的空间分布特征及电子间夹角的分布特征，显示出Wannier提出的原子的双电离反应机制的部分特性，从而验证了Wannier对近阈值下原子的双电离机制的推断。2，实验获得的五重微分截面与不同理论模型的计算结果进行了比较，研究表明DS6C理论模型能够对近阈值下氦原子的双电离进行较好的描述

中低能区He2++He碰撞反应转移电离机制研究

反应显微成像谱仪能够对离子-原子碰撞反应中的末态产物进行运动学完 全测量。本论文基于反应显微成像谱仪对70-400keV He 2+ -He 碰撞中转移电离机 制进行了实验研究。 通过对不同出射角度电子的能谱研究表明， ECC电子和速度分布在0和入射 炮弹速度之间的“分子化”特征电子是出射电子能谱的主要贡献，前者是动力学 两步过程的作用，后者可由“准分子”激发模型给予定性解释，“鞍点电子”仅 是后者的一部分。通过对不同平面内出射电子的速度分布研究发现出射电子主要 集中在散射平面内，而且其速度分布介于0与炮弹速度之间且前向出射，同时在 炮弹与靶核核间轴处有一极小值；在入射离子能量较低时，出射电子空间分布较 为对称，随着入射离子能量的增加，出射电子逐渐靠近炮弹或靶核；与此同时， 由于 态电子与 态电子相互干涉，出射电子在散射平面内的分布还与碰撞参数 相关，在大碰撞参数下， 态电子的作用更加明显，而在小碰撞参数下 态电子 的作用更加显著。实验结果表明准分子激发和动力学两步过程是中低能He2+ -He 转移电离过程的两种主要机制。

尖晶石中He离子辐照缺陷的演化及其对重金属原子的俘获效应研究

本项工作利用多种分析手段（FTIR、TDS、RBS/C、AFM、SEM），对100keV He离子不同剂量（0.5，2.0，8.0×1016cm-2）注入的尖晶石中缺陷的形成及其对重金属原子的俘获效应进行了研究。在FTIR谱上观察到了Al-O键的共振吸收峰随剂量增加向小波数方向移动和随退火温度升高向大波数方向回复；随退火温度增加这三组样品的晶格损伤均经历先增大后减小的过程，但随剂量不同晶格损伤开始增加的温度不同；注入剂量为2.0×1016 cm-2样品在退火过程中其表面发生了形变，随剂量增加样品表面发现起皮现象。上述差异被认为是样品中不同缺陷的形成所引起的。随后，尝试了利用He离子注入形成的空位型缺陷俘获重金属原子的方法在尖晶石中合成金属纳米颗粒。吸收光谱上SPR吸收峰的出现，证实了金属纳米颗粒的形成