中子反应同质异能态截面比的系统学

提出了中子反应同质异能态截面比的半经验公式.该公式含有一系统学参数,适应于产物核质量数44≤A≤197、同质异能态自旋0≤J_m≤12和基态自旋0.5≤J_g≤8的中子反应.在入射中子能量E_n<20MeV能区,对该系统学参数进行了系统学研究.通过获得的半经验公式和系统学参数,可以很好地再现已有实验数据,也可较好地预言无实验数据的同质异能态截面比或同质异能态截面.     

替代反应法测量锕系核(n,f)和(n,xn)截面

对于某些中子反应截面,在直接测量上存在困难。为了获得那些对核能发展极其重要的核数据,人们提出替代反应法,即利用带电粒子代替中子进行反应,从而实现中子反应截面间接测量的方法。现有替代反应一般采用非弹激发、转移等周边反应,涉及的角动量远比中子反应的大,需要理论修正,这造成了一定的困难。有鉴于此,提出利用轻带电离子的俘获反应作为替代反应,其复合核自旋与中子反应的相当,有效避免了自旋修正的困难。根据这个思路,采用236U的（α,f）和（α,2n）反应作为替代反应,成功提取了239Pu的（n,f）和（n,2n）反应截面,与ENDFB7评价库数据在误差范围内符合较好,表明了替代反应法的优越性,可以在核数据测量中推广应用。There are always difficulties in the direct measurement of reactions induced by neutron, in order to obtain the neutron induced nuclear reaction data which are extremely important for nuclear power development, the surrogate reaction method, which uses charged particles instead of neutron, was proposed. The existing surrogate reaction method generally chooses peripheral reaction as the surrogate reaction, such as inelastic scattering excitation or transfer reaction. As a result, the angular momentum involved is always far larger than the neutron induced reaction, which causes difficulties in the theoretical calculation. Because of this, we proposed to use light-ion capture reaction as the surrogate reaction, the compound nuclei spin is similar with that of the neutron induced reaction, so that the difficulties in spin correction can be effectively avoided. Based on this idea, the 239Pu(n, f) and (n, 2n) reaction cross sections were successfully extracted using 236U(α,f) and (α,2n) reactions as the surrogate reaction. The results coincide well with the data of ENDFB7 within the error range, which shows that the surrogate reaction method has its own superiority, and it can be applied in the measurement of nuclear data.     

光子穿透系数及同质异能态俘获截面的研究

合理地给出了复合核反应光子穿透系数及同质异能态俘获截面的计算公式,其中包括统计和非统计过程.通过求解级联γ退激过程计算光子穿透系数,既合理地扣除(n,γn)过程,又包括首次γ跃迁至中子分离能B_n以上能级的贡献.以4MeV以下中子和⁵⁹Co及¹⁰³Rh的反应为例,比较用不同方法计算的光子穿透系数,计算同质异能态俘获截面并和实验数据进行比较,最后对结果进行了分析和讨论.     

高电荷态同质异能态的寿命

分析了带电原子由于缺少内转换(同质异能态)或电子俘获跃迁(β衰变)引起的核寿命的变化.理论预言了随着电荷态的增加,内壳的电子在核表面的电子密度降低,内壳电子能级也降低,不稳定原子核的寿命由于前一原因而缓慢增加,但当内壳电子能级降到特殊能量时产生剧烈增加.比较了由于不同的跃迁能量和跃迁类型对内转换过程的半衰期的影响,并将计算的理论值与一些实验测量值进行了比对.并开发了进行这类计算的公共计算程序.     

(p,n)和(p,2n)反应激发函数的系统学研究

从普朗克(Planck)黑体辐射公式和实验测量数据出发,采用唯象的方法提出了包含两个可调参量,入射质子能量从阈能到150MeV,靶核质量数在44相似文献   

原子核与激光的相互作用(一)——激光引起的同质异能态衰变和γ Laser

用参量化的方法推导了激光引起的原子核同质异能态共振跃迁的几率,并考虑了激光频率宽度的效应.进而研究了基于以下概念发展γ激光器的可能性:即用强的可见光激光将长寿命的同质异能素转换到能量上近似兼并的短寿命同质异能素,并使后者达到粒子数反转.在分析了同质异能态的粒子占有数随时间变化的基础上,数值计算了这一途径所需要的激光强度.     

Ba(n,x)134Cs,134Ba(n,2n)133Ba,140Ce(n,2n)139Ce,142Ce(n,2n)141)Ce和23Na(n,2n)22Na反应截面的测量

用中子活化法相对于⁵⁴Fe(n,P)⁵⁴Mn反应,在13.50—14.80MeV中子能区测量了Ba(n,x)¹³⁴Cs,¹³⁴Ba(n,2n)¹³³Ba,¹⁴⁰Ce(n,2n)¹³⁹Ce,¹⁴²Ce(n,2n)¹⁴¹Ce和²³Na(n,2n)²²Na的反应截面.并将所测的结果和其他作者的结果进行了比较,中子能量是用⁹⁰Zr(n,2n)^89m+gZr反应和⁹³Nb(n,2n)^92mNb反应截面比法测定的.     

原子核高K同质异能态的诱发γ辐射

介绍了原子核高K同质异能态潜在的应用价值及国内外研究的进展。 总结了形成同质异能态的3种主要物理机制。 说明了高K同质异能态的应用原理是将其激发到更高的不稳定的K混合态上, 再发生诱发退激, 形成γ瀑, 释放其存储的能量。 同时又介绍了K混合态的3种主要产生机制。 最后分析了178Hfm2诱发退变的实验, 讨论了这些实验的区别和与角动量投影壳模型计算结果的差异。The nuclear isomer states have great potential value of application. The important experimental and theoretical researches are presented here. There are three kinds of physics mechanism for the formation of the isomer states. The principle of releasing the energy stored in the isomer is to excite it to higher states, K mixing states, which can spontaneously decay to the ground state forming the γ cascade. After introducting the three ways to form the K mixing states, we analyzed experiments on the most prospective isomer 178Hfm2, discussed the key differences between these experiments and suggested that the Projected Shell Model (PSM) can be helpful to confirm the occurrence of the  K mixing states and would work out characteristics of the induced decay.     

高自旋同质异能态束流的产生和应用

论述了高自旋同质异能态束流的物理意义.以RINKEN的HSIB为例,简略地叙述了高自旋同质异能态束流的产生、分离、传输及纯化的方法,并对高自旋同质异能态束流诱发核反应中放出的γ射线探测技术进行了论述. The physical motivations with high spin isomer beams were introduced. Taking HSIB of RIKEN as an example, the methods to produce, separate, transport and purify high spin isomer beams were described briefly, and the detection of γ rays emitted from the reactions induced by the high spin isomer beams was presented. Finally, the progress to develope the high spin isomers in the N =83 isotones as second beams was stressed.     

~(206)At的[лh_(1/2)vi_(13/2)~(-1)]10~-同质异能态研究(英文)

利用能量为６０－８０ＭｅＶ的~(１２)Ｃ束流,通过~１９７Ａｎ（~(１２)Ｃ,３ｎ）~２０６Ａｔ反应研究了~２０６Ａｔ核的高自旋能级结构．用７台ＢＧＯ（ＡＣ）ＨＰＧｅ探测器和一台用于探测低能γ射线的平面型ＨＰＧｅ探测器进行了γ射线的激发函数、γ－γ－ｔ符合及γ射线的角分布测量．基于这些测量,首次建立了包括２５条γ跃迁的~２０６Ａｔ高自旋能级纲图．确定了一个半寿命为（９０８±４００）ｎｓ、自旋和宇称为１０的同质异能态．基于较重的双奇核~(２０８,２１０ )Ａｔ能级结构的系统性,对~(２０６)Ａｔ的１０~－同质异能态进行了讨论．     

轻核(n,x)反应微分截面的实验测量

对本课题组十几年来的(n,x)反应实验研究工作进行了评述.介绍了屏栅电离室的特点、构造与工作原理.用屏栅电离室在北京大学4.5MV静电加速器上测量了1—7MeV中子6Li(n,t)4He和10B(n,α)7Li反应的微分截面与截面,对实验结果进行了讨论. Our research work on (n, x) reaction for more than one decade is reviewed. The characteristics, structure, and working principle of the gridded ionization chamber are discussed. Differential cross sections and cross sections of the~(6)Li(n, t)~(4)He and~(10)B(n, α)~(7)Li reactions were measured in the neutron energy range of 1—7 MeV by using the GIC method. Experiments were carried out at the 4.5 MV Van de Graaff accelerator of Peking University. Results of the measurement are discussed.     

14MeV中子引起的Pb(n,x)203Hg, W(n,x)182Ta和W(n,x)183Ta的核反应截面测量

利用活化方法测量了14MeV中子引起的Pb(n,x)²⁰³Hg,W(n,x)¹⁸²Ta和W(n,x)¹⁸³Ta的反应截面.中子注量由监督反应⁹³Nb(n,2n)^92mNb给出,中子能量利用⁹⁰Zr(n,2n)^89m+gZr和⁹³Nb(n,2n)^92mNb反应的截面比来确定.     

13.5—14.6MeV能区中子引起的50Cr(n,2n)49Cr和52Cr(n,2n)51Cr核反应截面的测量

报告了在13.5-14.6MeV中子能区，用活化法(以93Nb(n，2n)92mNb反应截面为中子注量标准)测得的50Cr(n, 2n)49Cr和52Cr(n, 2n)51Cr的反应截面. 由能量为13.5±0.3 ,14.1±0.2,14.4±0.3 和14.6±0.3MeV的中子引起的50Cr(n, 2n)49Cr反应截面值分别为3.4±0.2,6.8±0.3,21.5±1.0 和25.0±1.2mb，52Cr(n, 2n)51Cr的反应截面值分别为185±10,193±9,258±13 和332±16mb. 单能中子用T(d,n)4He反应获得，其能量用铌锆截面比法测定. 另外，为避免热中子引发的50Cr(n, 2g)51Cr对52Cr(n, 2n)51Cr反应截面的影响，在样品被辐照过程中对样品进行了包镉处理，并将实验结果与尽可能收集到的其它实验数据进行了比较.     

利用BUU模型研究11Li的核反应总截面和双中子剥去截面

发展了BUU模型,能够同时研究双中子晕结构核¹¹Li引起反应的核反应总截面和双中子剥去截面,计算中使用软的核物质状态方程和0.8倍的核子–核子碰撞截面,同时还用相对论平均场模型计算的中子和质子密度代替通常使用的方密度分布,计算结果可以很好地拟合不同反应系统的实验数据,假定对于晕核及其核芯核,彼此的核反应总截面与相互作用截面之间的差别相同,那么¹¹Li的双中子剥去截面可以表示成”Li及其核芯核⁹Li引起反应的核反应总截面之差,研究结果表明这一假定可以适用于高能,对于中能核反应需要更多的实验数据来检验.     

Cross section measurements for (n, p) reaction on stannum isotopes at neutron energies from 13.5 to 14.6 MeV

Utilizing the cross sections for <'93>Nb(n, 2n)<'93m>Nb or <'27>Al(n, a)<'24>Na reactions as monitors, the cross sections for the reactions <'115>Sn(n, p)<'115m>In, <'116>Sn(n, p)<'116m>In, <'117m>Sn(n, p)<'117>In and <'117>Sn(n, p)<'117m>In have been measured at neutron energy ranging from 13.5 to 14.6 MeV through activation technology. Then, the results of present work were compared with the published experimental data.     

13.5－14.6MeV中子能区锡的同位素的(n,2n)反应截面的测量

报道了在13.5－14.6MeV中子能区用活化法测得的112Sn(n,2n)111Sn,118Sn(n,2n)117Sn 和 124Sn(n,2n)123mSn的反应截面值. 中子注量用93Nb(n, 2n)92mNb或27Al(n,α)24Na反应截面得到.单能中子由T(d, n)4He反应获得. 同时还列举了已收集到的文献值以作比较.     

13.5—14·6 MeV能区中子引起的89Y39（n，2n）88Y39反应截面的测量

用^93Nb（n,2n）^92mNb和^90Zr（n,2n）^89m＋gZr截面比法测定中子能量,以^93Nb（n,2n）^92mNb反应截面作中子注量标准,用活化法测量了13．5-14．6MeV中子引起的^89Y（n,2n）^88Y的反应截面值。由（13．5±0．3）,（14.1±0．2）,（14.6±0．3）MeV中子引起的^89Y（n,2n）^88Y反应截面值分别为（759±42）,（835±42）和（958±53）mb。Cross section for （n, 2n） reaction on Yttrium have been measured at energy of 14 MeV neutrons from H（d, n）He by using activation technique. The ^93Nb（n, 2n）^92mNb reaction was used to monitor the neutron fluence, HPGe detector was used to detect the γ-rays. The cross section of ^89Y （n, 2n）^88Y reaction are 759 ± 42, 835 ±42, 958 ±53 mb for neutron energy 13.5 ±0.3, 14.1±0.2, 14.6 ±0.3 MeV, respectively.