直接法解超结构的改进

直接法用于求解晶体超结构，已证明是一种客观的、有效的方法．本文提出通过使各衍射组衍射数目相等或Ｅ值均衡指派，均可收到提高直接法解超结构能力的效果．有关算法已编入新版的ＳＡＰＩ程序 关键词：     

Investigation of neutron induced reactions on ^23Na by using Talys1.4

The neutron induced reactions on ^23Na are investigated by using the Talys1.4 program. The calculated results for the ^23Na（n, 2n）22Na reaction are found to agree with the experimental results. The cross sections of the residues of the（n, n）,（n, γ）,（n, p）, and（n, np） channels in the reactions are presented, and at the same time, the neutron induced reactions on22 Ne are also investigated.     

Identification of a New Band and Its Signature Inversion in ^174Re

High spin states in ^174Re are investigated via the ^152Sm（^27 AL,5nγ）^174Re reaction and γ - γ coincidence relationships are analysed carefully. A new band is identified due to its spectroscopic connection with the known π1/2^-[541] × ν1/2^-[521] band. This band is proposed to be the ground-state band built on the π1/2^-[541]× ,ν5/2^-[512] configuration in view of the low-lying intrinsic states in the neighbouring odd-mass nuclei. It is of particular interesting that the new band exhibits a phenomenon of low-spin signature inversion, providing a new situation for theoretical investigations.     

Evidence for a new resonance Σ^＊ （1380） with J^P=1/2^-＊

A new particle Σ^ ＊ with J ^P = 1/2^-was predicted by unquenched quark models with its mass around the well established Σ ＊ （1385） with J P = 3/2 ＋ .Here we re-examine some old data of the K^-p → Λπ^-π^ ＋ reaction.Firstly we re-fit the data for kaon beam momenta in the range of 1.0 - 1.8 GeV.Secondly we study the reaction at the energies around Λ＊（1520） peak.Both studies show evidence for the existence of Σ＊with J^ P = 1/2^-around 1380 MeV.Higher statistic data on relevant reactions are needed to clarify the situation.     

Measurement of the total reaction cross section for the mirror nuclei ^12N and ^12B

The mirror nuclei ^12N and ^12B are separated by the Radioactive Ion Beam Line in Lanzhou （RIBLL） at HIRFL from the breakup of 78.6 MeV/u 14N on a Be target. The total reaction cross-sections of ^12N at 34.9 MeV/u and ^12B at 54.4 MeV/u on a Si target have been measured by using the transmission method. Assuming ^12N consists of a ^11C core plus one halo proton, the excitation function of ^12N and ^12B on a Si target and a C target were calculated with the Glanber model. It can fit the experimental data very well. The characteristic halo structure for ^12N was found with a large diffusion of the protons density distribution.     

Measurement of the astrophysical S factor for the low energy ^2H（d,γ）^4He reaction

The γ-rays and protons from an Ed = 20 keV deuteron beam incident on a D-Ti target were measured. A branching ratio of the 2H（d,γ）^4He reaction versus the ^2H（d,p）^3H reaction of Гγ/Гp = （1.061 0.34） x 10.7 has been obtained, and the astrophysical S factor of the ^2H（d,γ）He reaction at the center of mass energy Ecm ≈ 7 keV of （6.0±2.4） ×10^6 keV.b was deduced.     

19F-NMR进展

19F-NMR技术由于其化学位移范围大、不易出现峰重叠及灵敏度高等优点,自上个世纪50年代出现以来,在分析光学异构体,生命科学等研究中有其特殊意义.在体内核磁共振技术中,19F-NMR与其他方法相比,在不损伤样品的条件下,就可进行实时定量监测.近30年,引人氟代指示剂进行体内19F-NMR的研究,含氟生物活性物质以及含氟材料的研究受到很大的重视,19F-NMR技术及其应用发展起来.从近10年的情况来看,含氟生物活性物质的研究以及在医药、农药和具有优异性能的含氟材料的研究应用受到很大的重视,这是近期19F-NMR研究发展的一个主要特点.     

Neutron beam optimization based on a ^7Li（p,n）^7Be reaction for treatment of deep-seated brain tumors by BNCT

Neutron beam optimization for accelerator-based Boron Neutron Capture Therapy（BNCT） is investigated using a ^7Li（p,n）^7Be reaction. Design and optimization have been carried out for the target, cooling system,moderator, filter, reflector, and collimator to achieve a high flux of epithermal neutron and satisfy the IAEA criteria.Also, the performance of the designed beam in tissue is assessed by using a simulated Snyder head phantom. The results show that the optimization of the collimator and reflector is critical to finding the best neutron beam based on the ^7Li（p,n）^7Be reaction. Our designed beam has 2.49×109n/cm^2 s epithermal neutron flux and is suitable for BNCT of deep-seated brain tumors.     

Determination of the strong coupling constant using available experimental data

We determine the strong coupling constant α s up to 4-loop in perturbative QCD.Testing QCD requires the measurement of α s over ranges of energy scales.In this analysis,the value of α s is determined from the unpolarized structure functions data points by minimizing the χ ^2 function between the theory result and experimental data.Using perturbative QCD calculations from threshold corrections,we obtain α s （M 2 Z ） = 0.1139±0.0020 at N ^3 LO which is in good agreement with the very recently results from the inclusive jet cross section in pp collisions at√ s=1.96 TeV.     

Primary result of ^236U measurement with accelerator mass spectrometry at CIAE

The rare isotope ^236U has a half-life of 2.342（3）×107 years, and is produced principally by thermal neutron capture on ^235U. The isotopic atom ratio of ^236U/^238U depends on the integral thermal neutron flux received by the material of interest. ^236U is potentially useful as a ＂fingerprint＂ for indicating the presence of neutron-irradiated uranium usually originating from nuclear activity. By extracting negative molecular ion UO^- from the uranium oxide target, simulating the ^236U^16O^- beam transport with ^238U^16O^- and ^208Pb2^16O^- pilot molecular ion beam, transporting the ^236U-containing ion beam with a high resolution injection magnet analyzer and electrostatic analyzer system, and finally identifying and detecting ^236U with a time-of-flight detector （TOF）, a method for AMS （Accelerator Mass Spectrometry） measurement of ^236U was established on the HI-13 Accelerator AMS system at China Institute of Atomic Energy.     

Improved Ligand-Field Theoretical Calculation of R-Line Pressure-Induced Shift of MgO：V^2＋

By means of an improved ligand-field theory, the ＂pure electronic＂ PS and the PS due to EPI of R line of MgO： V^2＋ have been calculated, respectively. The calculated results are in very good agreement with the experimental data. The behaviors of the pure electronic PS of R line of MgO：V^2＋ and the PS of its R line due to EPI are different. It is the combined effect of them that gives rise to the total PS of R line, which has satisfactorily explained the experimental results. The mixing-degree of ｜t2^2（^3T1）e^4T2〉 and ｜t2^3 ^2E〉 in the wavefunetion of R level and its variation with pressure have been calculated and analyzed. The comparison between the feature of R-line PS of MgO：V^2＋ and that of MgO：Cr^3＋ has been made.     

Study of ππ final state interactions in ψ（2S） →π^＋π^-J/ψ

The π^＋π^ transition of heavy quarkonia in decay ψ（2S） →π^＋π^-J/ψ is studied. With the BESII data on the decay ψ（2S） →π^＋π^-J/ψ, we update the values of coupling constants （gi） and chromopolarizability （αψ（2s）J/ψ） in this process.     

Structure Evolution in the Even-Even (124—134)~Xe with IBM2

We have investigated the structure evolution of the124-134Xe isotopic chain in the framework of the proton-neutron interacting model IBM2. The positive parity spectra of the ground state, quasi-β and quasi-γ bands are reproduced well. The staggering in124-130Xe are almost completely removed and the γ band agree well with the experiment data, even for the high-spin quasi-γ states. The key quantities of the collective structure evolution, including level energies, the B(E2) transition branching ratios, and the M1 excitations to 1+1mixer-symmetry states are analyzed by comparing with the experimental data. The parameters for representation of the Oπν(6) and SU πν(3) features in isotopes are examined. Both experimental data and theoretical results show that the shape phase transition of124 134Xe isotopic chain is from the SU πν(3)(triaxial rotation) to the Uπν(5)(vibration motion) with a considerable constituent of the Oπν(6) symmetry(γ-unstable rotation), where the shape phase transition rapidly takes place between the neutron number N = 76 and N = 78.     

Density fluctuation of the ^3He reaction-diffusion model in nonextensive statistical mechanics

In this paper the time-space correlation of density fluctuation of the 3He reaction-diffusion model is investigated where the equilibrium distribution is described by the generalized Maxwell Boltzmann distribution in the framework of Tsallis statistics. By using the density operator technique, the nonextensive pressure effect is introduced into the master equation and thus the generalized master equation is derived for the nonextensive system. This paper uses the ^3He reaction diffusion model to analyse the effect of nonextensive pressure on the fluctuation and finds that the nonextensive parameter q plays a very important role in determining the characteristics of the fluctuation waves.[第一段]     

Development and application of the intense slow positron beam at IHEP

This paper describes the development and application of an intense slow positron beam at IHEP with regard to its two main components. The Variable-Energy Positron Lifetime Spectroscopy (VEPLS) based on the pulsing system consisting of a chopper, a prebuncher and a buncher has been constructed in order to meet the needs of materials science development. At present, the time resolution of the VEPLS can easily reach about 386ps with a peak-to-background ratio of about 600:1. A plugged-in ²²Na positron source section for adjusting the newly built experimental station and for increasing the beam operation efficiency has been constructed. A slow positron beam with an intensity of 2.5×10⁵e⁺/s and the beam profile whose diameter is 10mm has been obtained; the moderation efficiency of the tungsten mesh moderator reaches 5.1×10^－4 as calculated with an original positron source activity of 52mCi.     

NMR碳谱谱峰检索系统

介绍了核磁共振(NMR)碳谱谱峰检索系统的程序设计原理、系统流程框图、检索比较算法和主要显示界面．系统数据库包含化合物核磁共振碳谱4万多张,能够根据未知物¹³C NMR波谱的谱峰个数及其化学位移值进行检索．结果得到未知化合物的有关信息及其标准波谱图．系统还允许用户将本专业的一些常用化合物的标准谱的信息以及图谱添加进数据库以供日后查询．     

Analysis of Neutron Double-Differential Cross Sections for n ＋ ^12 C Reaction Below 30 MeV

Based on the light nucleus reaction model （Nucl. Sci. Eng. 133 （1999） 218）, four aspects （neutron incident energy region, reaction channel analysis, the renewed level schemes and the optical model parameters） of n＋ ^12 C reaction are improved to calculate total outgoing neutron double-dilferential cross sections with modified LUNF code below 30 MeV. The calculated results agree fairly well with the experimental data at En = 14.1 MeV and 18 MeV. The analysis shows that the pre-equilibrium mechanism, which is exactly considered the conservation of energy, momentum and parity, dominates the whole reaction process. The contribution of the neutron emission from 5He to total energy- angular spectra is also considered properly. This modified LUNF code will be a useful tool to set up the file of neutron double-differential crass sections below 30 Me V in the neutron evaluation nuclear data library.     

^5He Emission in Neutron-Induced ^10B Reactions

In n ＋^10B reactions, ^5He cluster emission has been discussed with the updated level scheme and the new optical model parameters. In this paper the reaction channels related to ^5He emission are listed in detail. By using the new reaction model for light nuclei, the double-differential cross sections of total outgoing neutrons for n ＋ ^10 B reactions at En= 14.2 MeV have been calculated, and the results agree fairly well with the measurements. Particularly, in the energy-angular spectra the contribution from the 5He-emission to the total outgoing neutron double-differential cross sections has also been analyzed, and the partial energy-angular spectra of 60° at En= 14.2 MeV have been given. The calculated results indicate that once the 5He emission is taken into account, the fitting with the double-differential measurements of total outgoing neutrons at the low energy region could be improved. Therefore, to consider the ^5He emission properly in the reaction processes of light nuclei is necessary.     

Microscopic Study of Nuclear Level Densities and Thermal Properties in^56,57 Fe

We calculate level densities for ^56,57 Fe nuclei using BCS hamiltonian with inclusion of pairing interaction. The results of calculations show that the step structure observed experimentally has been supported by microscopic theory, Also the S-shaped energy and entropy as function of temperature have been obtained in theoretical calculations. Structures in the curves are interpreted as fingerprints of breaking Cooper pairs and quenching of pairing correlations.     

三种环氧孕甾衍生物的合成和光谱特性研究

合成了三种环氧孕甾衍生物：6-亚甲基-16α,17α-环氧孕甾-4-烯-3,20-二酮,6-甲基-16α,17α-环氧孕甾-4,6-二烯-3,20-二酮和6-甲基-16α,17α-环氧孕甾-4-烯-3,20-二酮。其中6-甲基-16α,17α-环氧孕甾-4,6-二烯-3,20-二酮未见文献报道。同时应用红光谱(FTIR)、紫外光谱(UV)、及核磁共振氢谱(1H NMR)对三种甾体化合物的结构进行了研究。结果表明,三种甾体化合物结构上的差异在FTIR,UV,1H NMR谱中有明显的特征并表现出一定的规律。