~(59)Co(n,p)~(59)Fe,~(59)Co(n,α)~(56)Mn,~(59)Co(n,2n)~(58)Co反应截面的测量

本实验用活化法测量了中子能量在12.8MeV到17.8MeV的~(59)Co(n,p)~(59)Fe,~(59)Co(n,α)~(56)Mn,~(59)Co(n,2n)~(58)Co三个反应道的反应截面值,实验的测量误差在3.3％—6.9％范围内. 本文还计算了反应截面测量误差的协方差矩阵,并将实验测量值与理论计算值进行了比较.另外,还对上述三个反应道的截面进行编评,给出了推荐的激发曲线.     

~(186)W(d,p)~(187)W,~(186)W(d,2n)~(186)Re,~(nat)Fe(p,x)~(56)Co和~(nat)Ti(a,x)~(51)Cr反应激发函数评价

考虑特征γ射线分支比、衰变常数和标准截面等修正,对带电粒子引起的核反应~(186)W(d,p)~(187)W,~(186)W(d,2n)~(186)Re,~(nat)Fe(p,x)~(56)Co和~(nat)Ti(a,x)~(51)Cr的激发函数进行了研究。全面收集了这些反应激发函数的实验测量数据,对这些实验数据进行了分析处理,应用数学方法对分析处理后的实验数据进行了拟合。经过评价,给出了50 Me V以下~(186)W(d,p)~(187)W,~(186)W(d,2n)~(186)Re,~(nat)Fe(p,x)~(56)Co和~(nat)Ti(a,x)~(51)Cr反应激发函数的推荐值。     

~(55)Mn(α,n)~(58m,g)Co,~(55)Mn(α,2n)~(57)Co和~(55)Mn(α,α′n)~(54)Mn反应的激发函数

用活化法和迭靶技术,在入射α粒子能量从10.4到26.5MeV范围内,测量了~(55)Mn(α,n)~(58m,g)Co、~(55)Mn(α,2n)~(57)Co和~(55)Mn(α,α′n)~(54)Mn反应的截面,并同激子模型理论计算作了比较,结果表明在上述反应中存在平衡前发射反应机制。     

Quantized (1, 0) ⊕ (0, 1) Fields

We find a mapping between antisymmetric tensormatter fields and the Weinberg 2(2j + 1)-componentbispinor fields. Equations which describethe j = 1 antisymmetric tensor field coincide with the Hammer-Tucker equations entirely and withthe Weinberg ones within a subsidiary condition, theKlein-Gordon equation. A new Lagrangian for the Weinbergtheory is proposed which is scalar and Hermitian. It is built on the basis of the concept ofWeinberg doubles. The origin of acontradiction between the classical theory, the Weinbergtheorem B – A = for quantum relativisticfields, and the claimed longitudity of the antisymmetrictensor field [transformed on the (1, 0) (0, 1)Lorentz group representation] after quantization isclarified. Analogs of the j = 1/2 Feynman–Dysonpropagator are presented in the framework of the j = 1 Weinberg theory.It is then shown that under a definite choice of fieldfunctions and initial and boundary conditions themassless j = 1 Weinberg–Tucker–Hammerequations contain all the information that the Maxwell equationsfor the electromagnetic field have. Thus, the formerappear to be of use in describing some physicalprocesses.     

~(100)Mo(n,2n)~(99)Mo,~(96)Mo(n,p)~(96)Nb和~(92)Mo(n,α)~(89m+g)Zr反应截面测量

本文报告了在E_n=13.40—14.79MeV中子能区用活化法以~(27)Al(n,α)~(24)Na截面为中子注量标准测得的~(100)Mo(n,2n)~(99)Mo,~(96)Mo(n,p)~(96)Nb和~(92)Mo(n,α)~(89m+g)Zr的反应截面,中子能量是用铌锆截面比法测定的。文中将实验测量值与理论计算值进行了比较,还对上述三个反应的截面进行了编评,给出了推荐的激发曲线。     

Magnetic properties of hole-doped SCGO, SrCr(8)Ga(4-x)M(x)O(19) (M?=?Zn, Mg, Cu)

We report changes in the magnetic properties of hole-doped SCGO, SrCr8Ga4O19, induced by replacing non-magnetic Ga3+ with both non-magnetic (Mg2+ and Zn2+) and magnetic (Cu2+) cations. The resulting solid solutions, SrCr(8)Ga(4-x)M(x)O(19) (M = Zn, Mg, Cu) have been studied by x-ray diffraction and magnetic susceptibility measurements. For all cases, at least 10% of Ga can be replaced by divalent cations resulting in oxidation of ≥5% of the Cr3+ d3 to Cr4+ (d2). The hole doping results in an increase in ferromagnetic interactions and reduces the magnetic frustration. In the SrCr(8)Ga(4-x)Cu(x)O(19) series an enhancement of the spin-glass-like transition is observed, T(f)～ 6 K, which we ascribe to the magnetic nature of the Cu2+ (d9) dopant.     

~(58)Ni(n,p),~(60)Ni(n,p),~(62)Ni(n,α)和~(54)Fe(n,p)反应截面的测量与评价

本实验用活化法测量了中子能量在13.60 MeV—17.77 MeV的~(58)Ni(n,p)~(58m+g)Co,~(60)Ni(n,p)~(60)Co和~(62)Ni(n,α)~(59)Fe三个反应道的反应截面值,并计算了反应截面测量误差的协方差矩阵。实验的测量误差在3％—7％范围内。本文还对上述三个反应截面及~(54)Fe(n,p)~(54)Mn反应截面进行了编译,推荐了从阈能到20MeV能区的激发曲线。     

Mo(d,x)~(95m)Tc,Mo(d,x)~(96g),Tc和Mo(d,x)~(97)Tc反应的激发函数

用活化法和迭靶技术,测量了入射氘核能量从3.2到13.3MeV范围内,Mo(d,x)~(95m)Tc,Mo(d,x)~(96g)Tc和Mo(d,x)~(97m)Tc反应的激发函数,并与复合核统计模型理论计算作了比较。     

快中子(n,α)和(n,p)反应的研究

快中子核反应数据,不论对反应堆和聚变堆的设计,还是对核反应机制和核结构的研究及其理论的发展均有着重要的意义．由于屏栅电离室的诸多特点,被用于快中子核反应截面、能谱及双微分截面的测量．作为系统研究的一部分,利用屏栅电离室在北京大学４．５ＭＶ静电加速器上和在４～７ＭｅＶ能区内,对４０Ｃａ、６４Ｚｎ、５８Ｎｉ、５４Ｆｅ、３９Ｋ的（ｎ,α）反应进行了成功的测量,并对５８Ｎｉ的（ｎ,ｐ）反应进行了初步的测量．实验给出了反应中出射粒子的微分能谱、角分布和反应截面．从测量结果来看,在所测能区内,角分布大致是９０°对称的,说明在此能区复合核反应机制起主要作用．The study of the charged particle emission reactions induced by 3～7 MeV fast neutrons is of considerable interest for both nuclear applications and the understanding of basic nuclear problems. For its many merits, twin gridded ionization chamber is used in the studies of (n,α) and (n,p) reactions. As a part of systematic investigation, the (n,α) reactions for some nuclei, such as 40 Ca, 64 Zn, 58 Ni, 54 Fe, 39 K have been studied. Cross sections...     

Eu_(0.9)M_(0.1)TiO_3(M=Ca,Sr,Ba,La,Ce,Sm)的磁性和磁热效应

EuTi0_3是直接带隙半导体材料,在液氦温度附近呈现反铁磁性,且具有较大的磁熵变,但是当其转变为铁磁性时,可以有效提高低磁场下的磁熵变.本文通过元素替代,研究晶格常数的变化和电子掺杂对磁性和磁热效应的影响.实验采用溶胶凝胶法制备EuTiO_3和Eu_(0.9)M_(0.1)TiO_3 (M=Ca, Sr, Ba, La, Ce, Sm)系列样品.结果表明:大离子半径的碱土金属离子替代提高了铁磁性耦合,有利于提高低磁场下的磁热效应.电子掺杂可以抑制其反铁磁性耦合从而使其表现为铁磁性.当大离子半径的稀土La和Ce离子替代Eu离子时,既增大了晶格常数也实现了电子掺杂,表现出较强的铁磁性.在1 T的磁场变化下,Eu_(0.9)La_(0.1)TiO_3和Eu_(0.9)Ce_(0.1)TiO_3的最大磁熵变分别为10.8和11 J/(kg·K),均大于EuTi0_3的9.8 J/(kg·K);制冷能力分别为39.3和51.8 J/kg,相对于EuTi0_3也有所提高.     

~(11)Li,~(14)Be,~(17)B的一个三体模型

假定~(11)Li,~(14)Be和~(17)B是由N=2Z核芯和两个外层中子组成的三体系统,核芯-中子和中子-中子间的作用为弱吸引指数势,不足以形成核芯-中子和中子-中子二体束缚态。本文的计算表明,核芯-中子-中子三体系统可形成束缚态,计算结果基本上解释了~(11)Li,~(14)Be,~(17)B的基态能量和异常大核半径的实验结果。     

~(50,48,46)Ti的(n,p)(n,α)和~(58)Ni的(n,2n)(n,p)反应截面的测量

本文叙述了从13.50 MeV到14.81 MeV中子能区用活化法相对~(21)Al(n,α)~(24)Na的反应截面,对~(50)Ti(n,α)~(47)Ca、~(48)Ti(n,p)~(48)Sc、~(46)Ti(n,p)~(46)Sc、~(58)Ni(n,2n)~(57)Ni、~(58)Ni(n,p)~(58m+g)Co五个反应截面的测量。并将所得的结果和其他作者的结果进行了比较。     

~(56)Fe(n,p)~(56)Mn反应截面测量

在E_n=12—18MeV,用活化法测量了~(56)Fe(n,p)~(56)Mn反应截面,在E_n=14.61±0.20MeV处做了绝对测量,结果为108.0±2.7毫巴.中子通量用伴随粒子法测定,并与反冲质子望远镜相比较,两种方法在1—2%的误差范围内一致.~(56)Mn的γ放射性用φ10×7.6厘米的NaI(Tl)闪烁谱仪测量,谱仪探测效率用4πβ-γ符合法标定的~(56)Mn标准源刻度.测量结果与现有数据进行了比较.     

(n,p)和(n,α)激发函数半经验计算方法

在En≤20MeV的情况下,忽略了粒子的二次发射过程,认为复合系统的形成截面是能量相关的,得到了理论模型清晰、公式形式简单的半经验计算方法.在靶核23≤A≤209的范围内,利用大量(n,p)和(n,α)反应的截面实验数据对可调参数进行了研究,得到了参数对靶核的N和Z以及入射能量的依赖关系.对得到的参数做了定性的解释,利用普适参数对(n,p)和(n,α)反应的激发函数做了预言,预言值在其误差范围内与实验数据一致. To simplify the calculation, some assumptions are considered at present work. The preequilibrium emission is the first step in the equilibrium process, which is characterized by exciton n=3 and "never come back" are considered at the preequilibrium emission process; the proton and alpha emissions are only competed with the neutron emission, the second particle emission is neglected. A semiempirical method of the cross section for (n, p ) and (n, α) reactions were obtained on the basis of evaporatio...     

РЕАКЦИЯ (γ, р) НА ИНДИИ

Иамеряется энергети ческое и угловое расп ределение φотопрото нов из индия, облучаемого γ-квантами с энергией E_γ=17,6 Мэв u 14,8 Мзв. При сравнении энерге тического и углового распределения было о бнару-жено, что значительная час ть протонов образует ся при эвапорации и лишь около 3% прямым φо тоэφφектом. Из энергетического р аспределения найден ы энергии возбуждени я E _β ^* ядра¹¹⁴Cd, 3,8; 4,9; 5,6; 6,3 и. 7,6 Мэв.     

Zur (γ,p)- und (γ,np)-Reaktion am Argon 40

Argon gas has been irradiated with 34 MeV bremsstrahlung. The yields of the reactions A⁴⁰(γ, p) Cl³⁹ and A⁴⁰ (γ, np) Cl³³ were determined relative to C¹²(γ, n) by β-counting. The resulting upper limits for the cross sections integrated to 28 MeV are 160 MeVmbarns for (γ, p), and 35 MeV mbarns for (γ, np). This does not confirm the anomalously high A⁴⁰ (γ, p)-cross section reported in the literature.     

РЕАКЦИЯ (γ, р) НА КОБАЛЬ ТЕ

- , Li(, ) ( =17,6. 14,8 MeV). , u . , gQ=0,74+-0,16 MeV ⁵⁸Fe E ^* : 6,76; 6,44; 5,90; 5,47; 4,98; 4,35; 3,50; 3,20 MeV. , .     

~(15)O-~(15)N,~(17)F-~(17)O库仑移位能

从Paris势和电磁相互作用出发,应用格林函数方法微观地计算了~(15)O-~(15)N,~(17)F-~(17)O库仑移位能.G矩阵的电荷非对称性的贡献较重要,比通常唯象的核力电荷非对称成分的贡献大一倍左右.     

~(12)C(~7Li,t)~(16)O和~(20)Ne(d,~6Li)~(16)O反应的研究

本文把用于处理重离子引起的单粒子转移反应的Goldfarb-Buttle方法推广到多粒子转移反应。计算了~(12)C(~7Li,t)~(16)O和~(20)Ne(d,~6Li)~(16)O反应,用了~(16)O的全相干波函数,考虑了某些反冲因素,并将结果与实验作了比较。