重离子裂变反应中的能级密厦参数和裂变几率

本工作从Ｎｉｌｓｓｏｎ单粒子能级入手,计算了形变核１８６Ｏｓ、１８７Ｉｒ、１８９Ｏｓ和１９３Ａｕ作为激发函数的固有能级密度参数ａｉｎｔ和有效能级密度参数（包括核集体运动效应）ａｅｆｆ．由这样能量相关的能级密度参数计算的裂变几率Ｐｆ（Ｕ）与本工作的裂变几率符合很好． Based on the single-particle levels given by Nilsson,the intrinsic and effective(with collective effects)level density parameters as a function of theexcitation energy for the 186Os, 187Ir, 189Os and 193Au deformation nuclei have been calculatedin the range of the excitation energy up to 150MeV. The calculated fission probabilities Pf(U) are consistent satisfactorily with the experimental data when a nonadiabtic estimation ofthe collective effects was used to calculate the nuclear level density parameters.     

Calculation of plasma characteristics of the sun

The ionization level and free electron density of most abundant elements (C, N, O, Mg, Al, Si, S, and Fe) in the sun are calculated from the centre of the sun to the surface of the photosphere. The model and computations are made under the assumption of local thermodynamic equilibrium (LTE). The Saha equation has been used to calculate the ionization level of elements and the electron density. Temperature values for calculations along the solar radius are taken from references.     

Island-growth of SiCGe films on SiC

SiCGe ternary alloys have been grown on SiC by hot-wall low-pressure chemical vapour deposition. It has been found that the samples cxhibit an island configuration, and the island growth of SiCGe epilayer depends on the processing parameters such as the growth temperature. When the growth temperature is comparatively low, the epilayer has two types of islands： onc is spherical island; another is cascading triangular island. With the increase of the growth temperature, the islands change from spherical to cascading triangular mode. The size and density of the islands depend on the growth duration and GeH4 flow-rate. A longer growth time and a larger GeH4 flow-rate can increase the size and density of the island in thc initial stage of the epitaxy. In our case, The optimal growth for a high density of uniform islands occurred at a growth temperature of 1100℃ for l-minute growth, with 10 SCCM GeH4, resulting in a narrow size distribution （about 30nm diameter） and high density （about 3.5 ×10^10 dots/cm2）. The growth follows Stranski- Krastanov modc （2D to 3D modc）, both of the islands and the 2D growth layer have face-centred cubic structure, and the critical thickness of the 2D growth layer is only 2.5 nm.[第一段]     

Simulation and analysis of 13N+p elastic resonance scattering

The ^13 N＋p elastic resonance scattering has been studied at the secondary radioactive beam facility of CIAE in inverse kinematics via a thick-target method. The excitation function for the ^13N（p,p） scattering was obtained in the energy interval of Ecru ≈0.5-3.2 MeV with a ^13 N secondary beam of （47.8±1.5） MeV. Careful analysis of the secondary beam components and extensive Monte-Carlo simulations enable the resolution of the experimental proton spectra. The resonance parameters for five low-lying levels in ^14 O were deduced by Rmatrix fitting calculations with MULTI7 and SAMMY-M6-BETA. The present results show general agreement with those from a recent similar work, and thus confirm the observation of a new 0^- level at 5.7 MeV in 140 with an improved width of 400（45） keV.     

Higher order bulk characteristic parameters of asymmetric nuclear matter

The bulk parameters characterizing the energy of symmetric nuclear matter and the symmetry energy defined at normal nuclear density ρ0 provide important information on the equation of state (EOS) of isospin asymmetric nuclear matter. While significant progress has been made in determining some lower order bulk characteristic parameters, such as the energy E0(ρ0) and incompress ibility K0 of symmetric nuclear matter as well as the symmetry energy Esym(ρ0) and its slope parameter L, yet the higher order bulk ...     

Effect of deuteron density distribution on the deduction of screening potential from the D（d,p）T reaction in Be metals

The D(d,p)T reaction in Be metal environments has been measured to investigate the electron screening effect in metals in an energy region of from 5.5 keV to 10 keV in a center of mass system (CMS) at a temperature of 121 K. The depth distribution of deuteron density in Be metals has an impact on the observed reaction yields. A model of deuteron density distribution in metal has been proposed to obtain the original yields. A screening energy of (116±46) eV has been obtained with the assumed deuteron density distribution model.     

Low-lying states and isospin excitation in the Ge isotopes

The level structure of ^64-70Ge isotopes has been studied within the framework of the interacting boson model-3（IBM-3） . The symmetry character in the proton and neutron degrees of freedom of the energy levels has been investigated. The isospin excitation states（T 〉 Tz） have been assigned for the ^64Ge（N = Z） nucleus. Some intruder states in these nuclei have been suggested. The calculated energy levels and transition probabilities are in good agreement with recent experimental data. The study indicates that the Ge isotopes are in transition from γ-unstable to vibrational.     

丰中子核91Y 的高自旋能级结构(英文)

丰中子核91Y 的高自旋能级结构通过82Se(13C, p3n)91Y 反应被再次研究了。新建立的包含几条关键能级的能级纲图澄清了以前研究中的几点不确定的地方。这几条能级具有Z=38 和N=56 子闭壳打破的特征,这涉及到张量力和自旋-同位旋依赖的中心力。High-spin level structure of the neutron-rich nucleus 91Y has been reinvestigated via the 82Se(13C, p3n)91Y reaction. A newly constructed level scheme including several key levels clarifies the uncertainties in the earlier studies. These levels are characterized by the breaking of the Z = 38 and N =56 subshell closures, which involves in tensor force and the spin-isospin dependent central force.     

气相中二氧化钒活化甲烷C-H键的理论研究

The gas-phase reaction of VO2+（1A1/3A′）+ CH4 to yield P1[V(OCH2) +＋H2O] and P2[(OCH2) +＋H2] has been studied using density functional theory (DFT) at the B3LYP/6-311++G (3df, 3pd)//6-311G(2d,p) level. And the reaction mechanism of activation of C-H bond of CH4 by VO2+ has been investigated. The computational results manifest that the reaction channel of forming H2 is the dominant one. The potential energy curve-crossing dramatically affecting reaction mechanism and reaction rate has been discussed.     

壳模型对143Pm核跃迁几率的计算

原子核跃迁几率理论计算和实验对比是分析描述原子核内部结构的主要手段之一。目前采用重离子核反应观测到^143Pm核（Z=61，N=82）高自旋能级结构:激发态最大能级达x=8397．6keV，对应自旋J=47／2（h=1）。利用核壳模型在计算^143Pm核能级结构及对应的自旋宇称基础上，系统地对其γ级联跃迁链以及纯E2跃迁进行了计算，并与实验数据进行对比。采用OXBASH程序的单粒子跃迁公式计算了^143Pm的跃迁几率。At present, the high spin state of ^143 Pm（Z = 61, N = 82） have been investigated. The level scheme of ^143Pm has been extended up to an excitation energy Ex = 8 397.6 keV and spin J =47/2（ h = 1 ）. Based on the nuclear shell model （NSM）, we have calculated the sequences of γ-ray transition rates and the pure E2 reduced transition probabilities of ^143Pm, and compared with experimental data. The formula of single-particle transition probability in the OXBASH code was applied in this paper.     

部分相干矩形阵列光束在自由空间中的谱移

根据广义惠更斯-菲涅尔衍射积分方法,推导出按矩形方式排布的部分相干高斯-谢尔模型阵列光束的光谱传输公式,定量分析了部分相干高斯-谢尔模型阵列光束在自由空间传输时轴上和离轴相对谱移的变化,并详细讨论了阵列参数和子光束的空间相干参数对相对谱移的影响。结果表明,部分相干高斯-谢尔模型阵列光束通过自由空间传输后,其相对谱移与光源处的谱密度、子光束的空间相干参数以及子光束数目和子光束间距等阵列参数有关,其中,阵列参数对相对谱移的影响非常显著。     

部分相干矩形阵列光束在自由空间中的谱移

根据广义惠更斯-菲涅尔衍射积分方法,推导出按矩形方式排布的部分相干高斯-谢尔模型阵列光束的光谱传输公式,定量分析了部分相干高斯-谢尔模型阵列光束在自由空间传输时轴上和离轴相对谱移的变化,并详细讨论了阵列参数和子光束的空间相干参数对相对谱移的影响。结果表明,部分相干高斯-谢尔模型阵列光束通过自由空间传输后,其相对谱移与光源处的谱密度、子光束的空间相干参数以及子光束数目和子光束间距等阵列参数有关,其中,阵列参数对相对谱移的影响非常显著。     

Development of long-life-cycle tablet ceramic adsorbent for geosmin removal from water solution

In this study, the tablet ceramic adsorbent (TCA), a silica/iron(III) oxide composite material, has been developed for geosmin (GSM) removal from the water solution. The physicochemical characteristics of TCA were examined with XRD, SEM, EDX and BET analyses. The sorption characteristics of GSM on TCA were investigated in a batch system. Attempts have been made to understand the adsorption kinetics, the effect of initial GSM concentration, solution pH, and reaction time.The batch experiments equilibrium data were well fitted to the Lagergren kinetic equation, which indicate the first-order nature adsorption. Over 82% of the GSM was removed by the TCA within 600 min at an initial concentration of 200 ng/L with 20 g/L of TCA dose. The batch and regeneration study indicated that the TCA is a cost-effective GSM adsorbent with sufficient mechanical strength to retain its physical integrity after long-time adsorption, and high regeneration performance for long-life-cycle application. Almost no second contamination (toxic sludge or leached iron) was observed after adsorption, and the gas resultant of thermal regeneration is harmless to atmospheric environment.     

Propagation of astigmatic stochastic electromagnetic beams in oceanic turbulence

In this paper, we investigate the characteristics of astigmatic stochastic electromagnetic beams through oceanic turbulence. Taking the electromagnetic Gaussian Schell-model (GSM) beam as an example, the analytic expressions for the spectral density and the spectral degree of polarization of the beam propagating the oceanic turbulence are derived. It is indicated that the spectral density along the z-axis of the GSM beam in the oceanic turbulence is severely influenced by the source correlation properties, as well as by the sea-related parameters. We show that the characteristics of the spectral density along the x-axis, y-axis and z-axis of astigmatic electromagnetic GSM beams passing through the oceanic turbulence are qualitatively different. Furthermore, we find that as the astigmatic coefficient becomes larger, the maximum value of the spectral density along the z-axis increases rapidly and the width of the spectral density becomes shorter rapidly. Finally, the results have shown that different strengths of astigmatism have different effects on the spectral degree of polarization.     

Off-axis Gaussian Schell-model beam and partially coherent laser array beam in a turbulent atmosphere

The propagation of an off-axis Gaussian Schell-model (GSM) beam in a turbulent atmosphere is investigated based on the extended Huygens-Fresnel integral formula. Analytical formulae for the cross-spectral density and corresponding partially coherent complex curvature tensor of an off-axis GSM beam propagating in a turbulent atmosphere are derived. Based on these formulae, the propagation properties of such kind of beam in a turbulent atmosphere are investigated in detail. Furthermore, the methods are extended to investigate the propagation properties of a partially coherent laser array beam in a turbulent atmosphere. The properties of an off-axis GSM beam and a partially coherent laser array beam in a turbulent atmosphere are closely related with the beam parameters and the structure constant of the turbulent atmosphere.     

部分空间相干光束在非Kolmogorov湍流大气中的有效曲率半径

激光在湍流大气中的传输有重要的理论研究和实际应用意义.以高斯-谢尔模型(GSM)光束作为部分空间相干光的典型例,基于非Kolmogorov谱和广义惠更斯-菲涅耳原理, 推导出GSM光束在非Kolmogorov湍流中的有效曲率半径的解析表达式. 重点研究了湍流参数(包括广义指数α,内尺度l₀,和外尺度L₀) 和传输距离z分别对GSM光束有效曲率半径的影响.结果表明, 有效曲率半径R_x(z)随α和z增加先减小然后再增大, 随L₀的减小而增大(3.6<α< 4),随l₀的增加而增大.并对结果做了物理解释.     

Generalized Stokes parameters of random electromagnetic vortex beams propagating through atmospheric turbulence

By using the extended Huygens–Fresnel principle, the analytical expressions for the generalized Stokes parameters of random electromagnetic Gaussian Schell-model (GSM) vortex beams propagating through atmospheric turbulence are derived, and used to study the changes in spectral Stokes parameters of random electromagnetic GSM vortex beams in atmospheric turbulence and to compare the results of random electromagnetic GSM vortex-free beams. The influence of atmospheric turbulence on the spectral Stokes parameters is analyzed. The validity of our results is interpreted physically.     

Angular spread of Gaussian Schell-model array beams propagating through atmospheric turbulence

The closed-form expression for the angular spread of Gaussian Schell-model (GSM) array beams propagating through atmospheric turbulence is derived. It is shown that the angular spread θ _sp of GSM array beams for the superposition of the cross-spectral density function is smaller than of those for the superposition of the intensity. However, the θ _sp of GSM array beams for the superposition of the intensity is less sensitive to turbulence than that for the superposition of the cross-spectral density function. For the superposition of the cross-spectral density function, θ _sp of GSM array beams with smaller coherence length σ ₀, smaller waist width w ₀, smaller beam number N, and larger separation distance x _d are less affected by turbulence than of those with larger σ ₀,w ₀,N, and smaller x _d ; while, for the superposition of the intensity, the effect of turbulence on θ _sp is independent of N and x _d . In addition, the angular spread is nearly the same for the two types of superposition when σ ₀ or w ₀ is small enough, or x _d is large enough. On the other hand, it is found that there exist equivalent GSM array beams for the two types of superposition which may have the same directionality as the corresponding fully coherent Gaussian beam in free space and also in turbulence.     

基于高斯锐化法的重叠峰分解方法研究

在放射性能谱测量中,由于探测器分辨率较低、待测样品中原子能级相近,往往会出现全能峰的重叠现象,对放射性核素的定性或定量检测带来较大的困难;常规的分离算法一般需要复杂的谱变换或大量的标准谱样本,不适用于现场测量中重叠峰的实时分解。因此,提出一种基于高斯锐化法的能谱重叠峰解析方法(GSM),结合峰锐化法的分辨率增强能力和褶积滑动变换法的平滑特性,可快速地识别、定位和解析γ能谱中的重叠峰。该方法首先对高斯函数进行锐化并做归一化处理,并以此作为变换算子,选择合适的高斯参数及窗宽度,通过对原始γ能谱数据进行褶积滑动变换,达到滤波和提高重叠峰分离度的目的;然后求解GSM成形处理后的谱线近似函数作为目标函数,并选取峰位中心附近若干点作为初始参数,最后以非线性拟合的方法进行重叠峰特征峰参数的解析。实验中,首先验证了该方法变换前后峰位、峰面积特征值的不变性,其次分别对重叠峰能谱段以及MCNP模拟的131I,137Cs,214Bi,206Bi和26Al混合放射源γ能谱进行方法验证。实验结果表明,该方法对于分离度大于0.375、信噪比大于40 dB的重叠峰具有较好分解效果,分解前后的峰位和峰面积的相对误差分别在1%和4.5%以内;对于γ能谱进行全谱解析后,重叠峰的峰位分离相对误差在1%以内,单峰的分离相对误差约为0.1%以内,且当变换算子的半宽度接近探测器能量分辨率时,重叠峰的分解结果更准确。该方法具备较好的噪声抑制性能,在全谱解析中无需进行能谱光滑及本底扣除等谱线预处理操作,且计算资源耗费少,分解精确度较高,便于能谱测量系统的嵌入式实时解谱应用,对放射性测量中能谱的现场快速解析具有实用性。     

部分相干光的杨氏干涉光强分布特点研究

基于部分相干光(GSM)互强度传播规律研究了部分相干光杨氏双缝干涉光强分布特点。采用数值分析方法研究了干涉条纹光强随狭缝的几何尺寸、观察距离和光束光学参数变化的规律。