Reinvestigation of the high spin states in ^（161）Er and enhanced E1 transitions in the N=93 isotones

High-spin states in ¹⁶¹Er have been studied experimentally using the ¹⁵⁰Nd(¹⁶O, 5n) reaction at a beam energy of 86 MeV. The relatively enhanced E1 transitions between the 5/2⁺[642] and 3/2^-[521] bands are observed in ¹⁶¹Er, and the B(E1) values are extracted experimentally. The systematics of the R(E1) values in the N=93 isotones are presented. It is found that the strength of the E1 transitions obviously exhibits angular momentum dependence, and the occurrence of the relatively enhanced E1 transitions could be attributed to octupole softness.     

一种基于SiPM的新型起始时间探测器研制

本文介绍了一种新型起始时间探测器的研制。该探测器的灵敏面积为60 mm×60 mm,利用120根直径为1 mm的塑料闪烁光纤分成两层错位紧致排布,且上下相邻的3根光纤作为一个探测单元,每个探测单元均采用硅光电倍增管从双端读出信号。采用90Sr放射源对单根光纤进行了性能测试,结果表明,闪烁光沿着光纤方向的有效传播速度约为17 cm/ns,对应的时间分辨优于600 ps。此外,利用中国科学院近代物理研究所第二条放射性束流线（RIBLL2）提供的240 MeV/u的15N次级束研究了该探测器的性能。束流测试结果表明:该探测器的时间分辨为（150±15）ps,纵向位置分辨为（1.8±0.2）cm,并且结合该探测器以及RIBLL2束流线外靶实验终端上的其他探测器,可以对实验中产生的5 ≤ Z ≤ 8的各种同位素进行非常好的粒子鉴别。     

Dipole bands in nucleus ^139Pm

High-spin states in nucleus ^139Pm have been studied using the reaction ^116Cd（^27Al, 4n）^139Pm. Two dipole cascades have been found. Spin and parity assignments were based on the Directional Correlation of Oriented Nuclei （DCO） ratios and systematic behavior in neighboring odd-proton nuclei. The level structures of ^139Pm are compared with those of the N = 78 isotone ^141Eu in which two dipole bands have been confirmed as magnetic rotational bands. The close similarity between them suggests that the dipole bands in ^139Pm may be magnetic rotational bands.     

139Pm核中磁转动带的研究

通过重离子熔合蒸发反应116Cd(27Al, 4n)布居了139Pm的高自旋激发态,用12台高纯锗探测器（HpGe）阵列进行了在束γ-γ 符合测量。 基于γ-γ符合关系及139Pm核已知的能级信息,建立了两条ΔI=1的负宇称带。 利用相邻核能级结构的系统性和依据半经典的核子-核子有效作用的理论模型（SPAC）对这两条带能级结构进行了定量计算, 认为它们属于磁转动带。 High spin states in 139Pm have been studied via the116Cd(27Al, 4n) heavy ion fusion evaporation reaction. The γ-γ coincidences were measured with 12 HpGe detectors. Based on γ-γ coincidence relationships and previously known levels in 139Pm, two ΔI＝1 negative parity bands have been established. From the systematic comparison with the neighbouring nuclei and semi classical effective interaction model (SPAC) calculations, the two bands were suggested as magnetic rotational bands.     

17F + p 厚靶实验对18Ne共振态性质的研究

实验通过17F+p共振弹性散射研究了复合核18Ne激发态中与天体核反应14O(α, p)17F相关的共振态性质。利用兰州放射性束流线(RIBLL)对弹核碎裂反应产生的放射性束17F进行了分离和提纯。经过降能后,能量为4.22 AMeV 的17F束流轰击在T2终端的厚氢靶(CH₂)_n上。　两套∆E-E Si探测器望远镜放置在两个不同的探测角度θ_lab≈2.3°和14°上,对反冲质子的角度和能量进行了测量。实验观测到了复合核18Ne的几条质子共振能级。通过R-Matrix理论程序对激发函数进行拟合,得到了共振态的能量、 自旋、 宇称和衰变宽度等共振参数。Resonant properties in18Ne relevant to the stellar reaction of 14O(α, p)17F have been investigated through a resonant elastic scattering of 17F+p. The 17F RI beam was produced via a projectile fragmentation reaction, and subsequently separated and purified by Radioactive Ion beam Line in Lanzhou(RIBLL). After a series of energy degradation,a 4.22 AMeV 17F beam bombarded a thick(CH₂)_ntarget at T2 terminal. Energy and angle of the recoiled protons were measured by two sets of ∆E-E silicon telescope at θ_lab≈2.3°,14° respectively. Several resonances in 18Ne were observed,and their resonant parametersincluding energy,spin parity and decay width have been determined by an R-Matrix analysis of the experimental excitation function.