Studies on the Ne(p, d)Ne and Ne(d, p)Ne reactions

Angular distribution measurements have been performed on the ²¹Ne(p, d)²⁰Ne and ²¹Ne(d, p)²²Ne reactions at E_p = 20 MeV and E_d = 10.2 MeV, respectively. In the ²¹Ne(p, d) ²⁰Ne reaction, the prolific formation of the J^π = 2⁺, 1.63 MeV state was characterized by l_n = 2 pickup, and the distribution associated with the 4⁴, 4.25 MeV state was suggestive of a weak l_n = 2 pickup. All of the observed l_n = 1 pickup strength is associated with formation of the 2⁻, 4.97 MeV ²⁰Ne level. The ²¹Ne(d, p)²²Ne results indicate that l_n = 2 transfer is involved in the formation of the 1.28, 3.36, 5.52, 5.63 and 6.65 MeV ²²Ne states. The angular distribution observed for the 2⁺, 4.46 MeV state and also the unresolved 5.33, 5.36 MeV composite of states required both l_n = 0 and l_n = 2 components in the associated distorted-wave Born approximation fits. The spectroscopic factors extracted from the present results are compared with those predicted by the Nilsson model without mixing: Applications of the angular momentum projection rule to the ²¹Ne(d, p)²²Ne reaction are considered.     

利用18O(6Li,d)22Ne反应研究22Ne Eα=470 keV共振态的性质

慢速中子俘获过程（s过程）是合成比铁重元素的重要途径之一。22Ne（α,n）25Mg反应是大质量AGB星中s过程主要的中子源,其中的22Ne主要通过14N（α,γ）18F（β+）18O（α,γ）22Ne反应链合成。该反应链中关键反应18O（α,γ）22Ne在天体物理感兴趣能区的截面非常低,其天体反应率主要来自于22Ne α分离阈附近低能共振态的贡献,但目前相关能级的共振参数严重缺失。在HI-13串列加速器的Q3D磁谱仪上,通过测量18O（6Li,d）22Ne反应的角分布,利用DWBA分析确定了22Ne分离阈附近共振能级E_α=470 keV的自旋宇称为0+,为后续计算18O（α,γ）22Ne的天体反应率打下了基础。About a half of the abundances of elements heavier than iron comes from the so-called slowneutron capture process (s-process) in Asymptotic Giant Branch (AGB) stars, with the 22Ne(α, n)25Mg reaction as one of the main neutron sources. In the beginning phase of AGB thermal pulse, 22Ne is produced by the 14N(α, γ)18F(β+)18O(α, γ)22Ne reaction sequence, in which the 18O(α, γ)22Ne reaction plays a key role. While the reaction rate of the 18O(α, γ)22Ne is mainly affected by several resonant states lying closely to the α threshold in 22Ne, up to now, the relevant 22Ne parameters are fragmentary in the energy region corresponding to the typical temperatures of s-process. The direct measurement of the 18O(α, γ)22Ne reaction rate is extremely difficult due to the very low cross section. In this work, we investigated the 22Ne resonant states via the 18O(6Li, d)22Ne reaction at the Beijing HI-13 tandem accelerator of China Institute of Atomic Energy. Based on the DWBA analysis, preliminary results showed that the spin-parity of 22Ne E_α=470 keV resonant states was assigned as 0+, which would make contributions to subsequent calculation for the reaction rate of the 18O(α, γ)22Ne.     

Projectile coulomb excitation of Ne and Ne

The static quadrupole moments of the first excited J^π = 2⁺ states in ²⁰Ne and ²²Ne and the reduced electric quadrupole transition probabilities of these states to the ground states were measured via projectile Coulomb excitation. The quadrupole moments were deduced from the shapes of γ-ray angular distributions. The results are: Q(²⁰Ne, 2⁺) = −0.20±0.05 b and Q(²²Ne, 2⁺) = −0.11±0.05 b. The transition strengths were deduced from yield measurements and by comparison with the yields of target γ-rays. The results are: B(E2; 0⁺ → 2⁺, ²⁰Ne) = 0.037±0.003 e² · b² and B(E2; 0⁺ → 2⁺, ²²Ne) = 0.025±0.002 e²· b². The results for the transition strengths are consistent with the results of accurate timing methods and resolve discrepancies between previous experiments. The results for the quadrupole moments are consistent with earlier measurements, although the mean values we obtain are slightly lower. The experimental measurements are compared with theoretical predictions and a detailed discussion is given of corrections to this type of reorientation experiment.     

原子核单粒子共振态的研究进展

共振是自然界普遍存在的有趣现象。在核物理领域,存在许多奇特现象,共振在其中扮演着重要角色。介绍了近期发展的RMF-CSM、RMF-CGF和RMF-CMR方法及其对原子核单粒子共振态的研究。给出了120Sn,31Ne等核的单粒子共振态的能量和宽度及其随质量数、形变的变化规律,分析了19C,31Ne和39Mg等核的晕形成的物理机制和在N=20附近能级反转的原因。特别是新发展的RMF-CMR方法,在描述稳定核和奇特核方面都取得了成功,支持Zr同位素存在巨晕的预言。Resonance is an interesting phenomenon in nature. In nuclear physics, resonance plays an important role in the formation of many exotic phenomena. This paper introduces the recently developed RMF-CSM, RMFCGF, and RMF-CMR methods and their researches on nuclear single-particle resonances. The energies and widths of the single-particle resonant states in 120Sn and 31Ne and their evolution to mass number and deformation are given. In addition, the physical mechanism of the halo formation in 19C, 31Ne and 39Mg and the cause of energy level inversion near N=20 are analyzed. In particular, the newly developed RMF-CMR approach has been successful in describing stable and exotic nuclei and supports the prediction that Zr isotopes exist in a giant halo.     

Optical pumping of the 2p3sP0 State of Ne (I = 3/2): g factor and metastability exchange cross section

A C.W. multi-mode dye laser is used to obtain by optical pumping an orientation of the 2p⁵ 3s³P₀ (F = 3/2) state of ²¹Ne. A magnetic resonance experiment leads to the measurement of the g factor g (³P₀) = 3.027 (8) × 10⁻⁴ to be compared with the theoretical prediction (3.025(6) × 10⁻⁴). One obtains also the metastability exchange cross section σ(³P₀) = 18.4 ± 4 Ų for collisions between metastable (³P₀) Ne atoms and ground state Ne atoms. This result is compared with other measurements and theoretical evaluation.     

Intermediate Energy Pion-20Ne Elastic Scattering in the α+16O Model of 20Ne

We present an analysis of π-²⁰Ne elastic scattering at intermediate energy basing on the α+¹⁶O model of the ²⁰Ne nucleus and in the framework of Glauber multiple scattering theory. Satisfactory agreement with the general features of the experimental data of pion elastic scattering on the neighboring 4N-type nuclei is obtained without any free parameters. Compared with the experimental angular distributions of pion elastic scattering on ¹²C, ¹⁶O, ²⁴Mg, and ²⁸Si nuclei, the diffractive patterns and the positions of the dips and peaks in the angular distributions of π-²⁰Ne elastic scattering are reasonably predicted by the calculations.     

The pattern of mode competition between two frequencies produced by mode split technology by tuning of the cavity length

A new method is used for studying the mode competition of HeNe lasers. The method used is: (i) to make a small frequency split by using laser longitudinal mode split technology, (ii) to tune the cavity length in order to move the two mode split frequencies along the frequency axis and (iii) to use different ration between ²⁰Ne and ²²Ne in the laser tubes. In some ranges of lasing bandwidth, one mode split frequency will extinguish due to mode competition. And in other ranges, two mode split frequencies will work altogether. At the boundary between these two ranges, the process of intensity variation, from zero to maximum or in the opposite direction, of the split frequencies can be seen clearly. The pattern is dependent on the ration between ²⁰Ne and ²²Ne.     

A New Calculation of Rotational Bands in Alpha-Cluster Nuclei

One of the cluster behaviors observed in light nuclei such as ²⁰Ne and ⁴⁴Ti is the presence of an alpha particle rotating around a double magic number core. In this work, a theoretical method is used for investigation of rotational spectra of two-particle cluster states. To this end, Deng-Fan potential in addition to Hellman potential is used as the core and cluster potential. Next, given the Wildermuth condition, and proper quantum numbers describing the relative motion of the alpha particle and core, the rotational levels of ²⁰Ne and ⁴⁴Ti isotopes are calculated. Our studies show that the results are in good agreement with the available data.     

20Mgβ衰变谱学与15O(α,γ)19Ne反应(英文)

15O（α,γ）19Ne（p,γ）20Na反应链是高温CNO循环向快速质子俘获过程突破的一条关键路径,相关的反应率输入量可通过20Mg的β衰变可布居19Ne共振态并测量其衰变性质来获得。通过高效率高精度地测量20Mg β衰变中产生的质子与γ射线得到了20Mg衰变的详细信息,并构建了完整的衰变纲图,还进行了19Ne 4 033 keV共振态衰变性质的探索,获得了该态在20Mg β衰变中被布居的分支比上限。通过比20Mg和20O镜像能级跃迁的结果确认了同位旋非对称性,为检验相关理论模型提供了精确的实验数据。对于突破路径中有重要影响的19Ne 4 033 keV共振态的性质,有待更高统计的实验进一步研究。The breakout from the hot CNO cycle to the rapid proton capture process can occur via the 15O(α,γ)19Ne(p,γ)20Na reaction sequence, and the β decay of 20Mg can be used as an alternative method to characterize some specific resonances, which will provide detailed nuclear structure input for reaction rate calculations. The reliable information on the decay properties and structure of 20Mg was obtained by measuring the emitted particles and γ-rays in the β decay with high efficiency and high resolution. Attempt was also made to search for the decay channels associated with the 4 033 keV resonance in 19Ne. To test fundamental symmetries, the transitions in the mirror decays of 20Mg and 20O were compared. The precise experimental data presented here would be important to constrain the theoretical calculations. It is desirable to clarify the astrophysically relevant problem by further experiments with improved statistics on the basis of the present work.     

On the Difference and Similarity Between Elastic Scatterings of Ne + C and O + O1

Based on the LCNO model with double alpha transfer and on the optical model, the experimental excitation functions and the angular distributions of ²⁰Ne + ¹²C and ¹⁶O + ¹⁶O elastic scatterings are respectively reproduced by using approximately equal parameters of optical potentials. The difference and the similarity exhibited in the elastic scattering excitation functions of these two systems are naturally explained.     

Analysis of Gross Resonant Structures in 12C+12C and 16O+12Ne Systems Using Deep Optical Potentials

Abstract Within the framework of the estended optical model, the gross resonant structures of the fusion escitation functions and the elastic scattering excitation functions for the ¹²C+¹²C and the ¹⁶O+²⁰Ne systems are described well by using deep optical potentials. The origin of the gross resonant structures and the effect of the deep potential and the parity-dependent potential are discussed.     

Studies on the track formation mechanism of the heavy ions in CR-39

The bulk etch rate for two types of CR-39 detector was measured as a function of temperature and the activation energies of bulk etching was determined. Experimental values of track etch rate were derived directly from the function of the succesive measured track length vrs. etching time for ²⁰⁹Bi, ¹²⁹Xe and ²⁰Ne ions.

The maximum etchable length of 13 MeV/u ²⁰⁹Bi and 13.04 MeV/u ¹²⁹Xe ions have been measured at and below these energies. A comparison of the measured and calculated track length data is presented.     

Fusion oscillations for symmetric light heavy-ion systems

The low-energy fusion cross section for ²⁰Ne+²⁰Ne has been measured. The data extend the systematics on fusion oscillations for such light symmetric systems. A simple extension of the usual barrier penetration model displays the decisive role of the symmetrisation of the system. It is also capable of qualitatively explaining the trends in this effect, in particular its decreasing importance as the mass of the system increases. The structure is essentially due to the sharpness of the cut-off of transmission coefficients as a function of angular momentum. The curvature of the Coulomb barrier is important in determining these coefficients and it is shown that the required values of this quantity are consistent with reasonable values of the surface diffuseness of the nuclear potential.     

Skyrme型N∧相互作用下超越平均场模型的∧超核研究

使用超越平均场Skyrme-Hartree-Fock（SHF）模型对_∧9Be,_∧∧10Be,_∧13C和_∧21Ne进行计算,采用SLy4参数组的Skyrme力作为NN相互作用力,采用最近提出的SLL4参数组的Skyrme力作为N∧相互作用。计算中包含了超子的自旋-轨道力以再现单粒子态的自旋-轨道能级分裂和不交叉效应,并采用BCS方法处理对力。讨论了不同组态超核的相关性质,包含12C⊗∧[000]1/2+,12C⊗∧[110]1/2-,12C⊗∧[101]3/2-和12C⊗∧[101]1/2-及8Be⊗∧[000]1/2+,8Be⊗∧[110]1/2-,8Be⊗∧[101]3/2-和8Be⊗∧[101]1/2-。计算了_∧9Be,_∧13C的低激发能谱并与实验值进行了比较。结果表明,采用的超越平均场SHF模型能很好地再现∧超子占据s_∧轨道的正宇称能级。对8Be的计算结果表明该模型可以很好地再现8Be的集团结构,可以得出_∧9Be的真实超核态能级和9Be类似态。对_∧9Be及_∧13C的计算均再现了自旋双重态（3/2+,5/2+）,但是得到的双重态能级差依然与实验值有出入。此外,对于上述超核体系均在∧超子占据∧[000]1/2+轨道时产生了收缩效应。还对_∧21Ne进行了计算并和超越平均场RMF模型计算结果进行比较,发现两者计算结果虽有细节上的出入,但是结果基本一致。The beyond-mean-field Skyrme-Hartree-Fock approach is adopted to investigate the properties of _∧9Be, _∧∧10Be, _∧13C and _∧21Ne. The nucleon-nucleon (NN) interaction SLy4 and the nucleon-hyperon(N∧) interaction Skyrme-type SLL4 are used. The spin-orbit force of hyperon is included to show the spin-orbit splitting and non-crossing effect with BCS method to deal with pairing force. Energies of different configurations, such as 12C⊗∧[000]1/2+, 12C⊗∧[110]1/2-, 12C⊗∧[101]3/2-, 12C⊗∧[101]1/2-, 8Be⊗∧[000]1/2+, 8Be⊗∧[110]1/2-, 8 Be⊗∧[101]3/2- and 8Be⊗∧[101]1/2- are given and used to study the effects of ∧ occupying different orbitals. The calculated energy spectra, including both positive-and negative-parity levels, are given and compared to the experimental data. The observed positive-parity spin-doublet (3/2+,5/2+) are successfully reproduced, but the energy difference needs further investigation. The two well known band structures corresponding to the genuine hypernuclear states and the 9Be-analog states are also obtained and compared with the observed ones. The shrinkage effect of ∧ occupying ∧[000]1/2+ is investigated through the density distributions of nuclear core. And finally the calculation results of _∧21Ne are given and compared with the results of RMF method, which are nearly the same but with differences in some details.     

Measurement of the range of 77.1 and 95 MeV/n Ne ions

The ranges and their dispersion for 77.1 and 95 MeV/n ²⁰Ne ions in CR-39 track detector were measured and compared with those calculated by the TRIM-90.05 computer code.     

A study of the Li(p,n)Be reaction by the neutron threshold technique

The reaction ⁶Li(p,n)⁶Be has been studied by slow-neutron detection, with particular attention to the ⁶Be ground state threshold. The detector response was calculated by a Monte Carlo technique and verified with a measurement of the ⁷Li(,n)¹⁰B threshold. An analysis of the shape of the ⁶Be threshold indicated that both s- and p-wave neutrons contribute significantly to the reaction. The results depend on what mode of decay is assumed for the ground state of ⁶Be. If a two-stage process is assumed, with either an alpha particle and an unbound diproton or ⁵Li and a proton as intermediate state, the width is found to be 95±28 keV and the Q-value obtained for the ⁶Li(p,n)⁶Be reaction is −5074±13 keV. It was not possible to detertmine which process is predominant. No higher thresholds in the slow neutron yield up to 4 MeV of excitation in ⁶Be were observed. The data above the ground state threshold are consistent with a broad excited state of ⁶Be or with the occurrence of other neutron-producing reactions.     

CuTe,Cu2和Cu2Te的结构与势能函数

在Cu和Te的RECP(Relativistic Effective Core Potential)近似下,运用B3LYP方法,在LANL2DZ基组水平上对CuTe,Cu₂和Cu₂Te分子体系的结构进行优化计算.结果表明,CuTe和Cu₂分子的基电子状态分别为²Π和¹∑_g⁺,Cu₂Te分子的基态为单重态的C_2V构型,其电子状态为¹A₁.同时还计算了Cu₂Te分子基态的离解能、力常数和振动频率.采用最小二乘法拟合出CuTe和Cu₂分子Murrell-Sorbie势能函数参数.在此基础上,运用多体展式理论方法导出Cu₂Te分子基态势能函数的解析表达式,其势能面准确复现了平衡态的结构特征.     

122~125Sn中子谱因子的实验研究

多个Sn同位素位于慢速中子俘获（s-）过程路径上,其中子谱因子可用于计算ASn（n,γ） A+1Sn直接辐射俘获的天体物理反应率,并可研究Sn同位素对s-过程核合成的贡献。本工作在中国原子能科学研究院HI-13串列加速器Q3D磁谱仪上,对实验室系下8°~66°范围内的122,124Sn（d,p）和（p,d）单中子转移反应角分布进行了测量。利用DWBA理论计算了转移反应角分布,并提取了122-125Sn的基态以及123,125Sn第一激发态的中子谱因子。其中,122Sn和124Sn的基态中子谱因子是首次从实验上获得。由于本工作成功鉴别开了123,125Sn的基态和第一激发态的效应,因此给出的谱因子比前人的结果更可信。Several Tin isotopes are on the path of slow neutron capture (s-) process, and the direct components of (n, γ) reactions can be derived from their neutron spectroscopic factors. In the present work, the angular distributions of 122,124Sn(p, d) and (d, p) reactions are obtained using the high-precision Q3D magnetic spectrograph in Beijing HI-13 tandem accelerator in China Institute of Atomic Energy. The distorted-wave Born approximation (DWBA) calculations are performed to extract the neutron spectroscopic factors of the ground state of 122-125Sn and the first excited state of 123,125Sn. The neutron spectroscopic factors of the ground state of 122Sn and 124Sn are firstly obtained in this work. As the events of the ground state and first excited state of 123,125Sn can be distinguished clearly by our experiment, the neutron spectroscopic factories of 123,125Sn are more reliable.