230U重离子衰变的观测

利用35MeV的质子束轰击ThO₂粉末靶,通过²³²Th(p,3n)反应产生²³⁰Pa核,经用放射化学方法分离出²³⁰Pa核并制成²³⁰Pa→²³⁰U测量源.用聚乙烯对苯二酸酯固体核径迹探测器记录其发射的重离子径迹.经248天的收集,观测到了两个²³⁰U→²⁰⁸Ph+²²Ne衰变事件,相对于α衰变的分支比为(1.3±0.8)×10^－14.     

89Ru的β缓发质子衰变性质

藉助氦喷嘴带传输系统,采用“p-γ”符合的鉴别原理,成功地合成与鉴别了⁵⁸Ni(³⁶Ar, 2p3n)反应产生的核素⁸⁹Ru,并研究了它的β缓发质子衰变性质.实验给出⁸⁹Ru的衰变半衰期为(1.2±0.2)s, 测定了它的β缓发质子能谱,提取出了⁸⁹Ru经缓发质子衰变布居到子核⁸⁸Mo的2⁺和4⁺态的相对终态分支比(100∶6).通过与统计模型计算结果进行对比,初步指定了⁸⁹Ru基态的自旋 宇称(5/2⁺或7/2^±)和质量过剩(-59.5 MeV).     

稀土区质子滴线附近新的β缓发质子衰变

用重离子束³⁵Ar轰击缺中子同位素靶⁹²Mo,⁹⁶Ru和¹⁰⁶Cd产生了质子滴线附近的β缓发质子先驱核¹²⁵Nd,¹²⁸Pm,¹²⁹Sm,¹³⁷Gd和¹³⁹Dy.配合氦喷嘴带传输系统用“p-γ”符合方法对它们进行了肯定的鉴别.它们的半衰期分别为：0.60(15)s,1.0(3)s,0.55(10)s,2.2(2)s和0.6(2)s.用统计模型理论计算对实验测定的¹²⁵Nd, ¹²⁹Sm,¹³⁷Gd和¹³⁹Dy的,和从前报道的¹²¹Ce,¹³⁵Gd的β缓发质子衰变的能谱和分支比进行了拟合.提取出¹²¹Ce, ¹²⁵Nd, ¹²⁹Sm,¹³⁵Gd, ¹³⁷Gd和¹³⁹Dy的基态自旋-宇称分别为5/2^±,5/2^±,1/2⁺(或3/2⁺),5/2⁺,7/2^±和7/2⁺.实验初步指认的基态自旋 宇称值与Nilsson能级图的预言值相符间接表明这6种核素的基态具有大形变,形变参数β₂在0.3左右.     

Ba同位素的截面测量

用60MeV/u¹⁸O离子轰击天然铀靶,通过²³⁸U(¹⁸O,X)反应产生钡的放射性同位素.使用放射化学分离方法从被照射过的铀靶中分离出Ba,用HPGeγ射线探测器测量Ba样品的γ射线谱,经对所得时间累计谱的处理和分析得到了Ba同位素的产生截面,并观察到Ba同位素分布中的双峰分布现象.     

142Ce的新激发态及其经验壳模型研究

利用420MeV⁸²Se轰击¹³⁹La引起的深部非弹反应和在束γ谱学方法研究了¹⁴²Ce的中高自旋激发态.识别出了激发能为2625,2995和3834keV的3个新能级,自旋、宇称分别被指定为8⁺,9^(－)和11^(－).发现这些能级非常好地符合N=84偶偶核转晕能级的系统性.利用经验壳模型计算了¹⁴²Ce的中高自旋激发态的激发能,计算结果比较好地重现了实验值.对它们的结构进行了讨论,表明在¹⁴²Ce的中高自旋激发态中以单粒子激发为主     

掺氢、掺氮碳纳米线的合成及其焊接

利用一种有效而别致的双离子(N⁺和Ar⁺)辐照和热处理技术合成并焊接无定形碳纳米线(ACNWs).实验样品用高分辨透射电子显微镜(HRTEM)进行了表征证实,适当搭配的双离子辐照与热处理的结合将会引起多壁碳纳米管无定形化并导致相互交叉纳米线的焊接.此外碳结构相变中的原子演化也在目前已有的概念基础上进行了简单地讨论. 关键词： 无定形碳纳米线 相变 透射电子显微镜     

Determination of the stellar reaction rate for 12C（α,γ）16O： using a new expression with the reaction mechanism

The astrophysical reaction rate of 12C(α, γ)16O plays a key role in massive star evolution. However, this reaction rate and its uncertainties have not been well determined yet, especially at T9=0.2. The existing results even disagree with each other to a certain extent. In this paper, the E1, E2 and total (E1+E2) 12C(α, γ)16O reaction rates are calculated in the temperature range from T9=0.3 to 2 according to all the available cross section data. A new analytic expression of the 12 C(α, γ)16 O reaction rate is brought forward based on the reaction mechanism. In this expression, each part embodies the underlying physics of the reaction. Unlike previous works, some physical parameters are chosen from experimental results directly, instead of all the parameters obtained from fitting. These parameters in the new expression, with their 3σ fit errors, are obtained from fit to our calculated reaction rate from T9=0.3 to 2. Using the fit results, the analytic expression of 12C(α, γ)16O reaction rate is extrapolated down to T9=0.05 based on the underlying physics. The 12C(α, γ)16 O reaction rate at T9=0.2 is (8.78 ± 1.52) × 1015 cm3s-1mol-1. Some comparisons and discussions about our new 12 C(α, γ)16 O reaction rate are presented, and the contributions of the reaction rate correspond to the different part of reaction mechanism are given. The agreements of the reaction rate below T9=2 between our results and previous works indicate that our results are reliable, and they could be included in the astrophysical reaction rate network. Furthermore, we believe our method to investigate the 12C(α, γ)16O reaction rate is reasonable, and this method can also be employed to study the reaction rate of other astrophysical reactions. Finally, a new constraint of the supernovae production factor of some isotopes are illustrated according to our 12C(α, γ)16O reaction rates.     

Field Emission Enhancement of Carbon Nanotubes by Surface Modification

By employing a multi-walled carbon nanotube （MWCNT） film as the substrate, we obtain Fe tipped carbon nanorods or carbon nanoparticles grown on the outer walls of MWCNTs by combining sputtering deposition of Fe films and rf plasma enhanced chemical vapour deposition at high temperature. Scanning electron microscopy and high-resolution transmission electron microscopy are used to examine the structure of carbon nanorods and carbon nanoparticles. In addition, the formation mechanism is discussed briefly. The electron field emission tests indicate that the turn-on field （at 10μA/cm^2） of the treated MWCNT films decreases from 2.4 V/μm to O. 79 V/μm and the field emission current is relatively stable. The enhanced field enhancement factor, increasing emission densities coming from the grown nanorods and nanoparticles, and H terminated by H plasma a11 are responsible for the enhancement of the field enhancement factor.     

缺中子稀土区滴线附近新的β缓发质子衰变

用重离子束³⁶Ar和³²S轰击缺中子同位素靶⁹²Mo,⁹⁶Ru和¹⁰⁶Cd产生了质子滴线附近的β缓发质子先驱核¹²⁵Nd,¹²¹Ce,¹²⁸Pm,¹²⁹Sm,¹³⁵Gd,¹³⁷Gd和¹³⁹Dy.配合氦喷嘴带传输系统用"p-γ"符合方法对它们进行了首次肯定的鉴别.它们的半衰期分别为:0.60(15)s,1.1(1)s,1.0(3)s,0.55(10)s,1.1(2)s,2.2(2)s和0.6(2)s.用统计模型理论计算对实验测定的¹²⁵Nd,¹²¹Ce,¹²⁹Sm,¹³⁵Gd,¹³⁷Gd和¹³⁹Dy的β缓发质子衰变的能谱和分支比进行了拟合.提取出¹²⁵Nd,¹²¹Ce,¹²⁹Sm,¹³⁵Gd,¹³⁷Gd和¹³⁹Dy的基态自旋-宇称分别为5/2^±,5/2^±,1/2⁺(或3/2⁺),5/2⁺,7/2^±和7/2⁺.实验初步指认的基态自旋(宇称值与Nilsson能级图的预言值相符间接表明这6个核素的基态具有大形变,形变参数β₂在0.3左右.     

198Pb低位能级结构研究

用100MeV ¹⁶O束流轰击厚的天然Re,产生了具有β⁺/EC衰变性质的核素¹⁹⁸Bi(¹⁹⁸Pb的母核).完全在在束的实验条件下用γ-γ符合测量方法研究了¹⁹⁸Bi的衰变γ线,确定了¹⁹⁸Pb的八个能级,识别出了¹⁹⁸Pb低位态能级退激的五条新γ线,从而进一步丰富了¹⁹⁸Pb的低位态能级结构.