Deuteron inelastic scattering on 6Li and 7Li nuclei within the three-body cluster model

The problem of the deuteron interaction with lithium nuclei,treated as a system of two coupled pointlike clusters,is formulated to calculate the cross sections of the d+Li reaction.The d+Li reaction mechanism is described using the Faddeev theory for the three-body problem of deuteron-nucleus interaction.This theory is slightly extended for calculation of the stripping processes ^6Li(d,p)^7Li,^7Li(d,p)^8 ,^6Li(d,n)^7 Be,and ^7Li(d,n)^8 Be,as well as fragmentation reactions yielding tritium,a-particles,and continuous neutrons and protons in the initial deuteron kineticenergy region Ed=0.5-20 MeV.The phase shifts found for d+^6Li and d+^7Li elastic scattering,as part of the simple optic model with a complex central potential,were used to find the cross sections for the 6^Li(d,yM)^8 and ^7Li(d,yE1)^9 Be radiation captures.The three-body dynamics role is also summarized to demonstrate its significant influence within the d+^7Li system.     

Astrophysical Reaction Rates of the ^8Li（p, τ）^9Beg.s. Direct Capture Reaction

Based on the angular distribution of the ^8Li（d, n）^9Beg.s, reaction at Ec.m. = 8.0 MeV and distorted wave Born approximation analysis, the single particle spectroscopic factor S1,3/2 for the ground state of ^9Be = ^8Li×p is derived to be 0.64 ± 0.21. In addition, we deduce the astrophysical S-factors and rates of the ^8Li（p, γ）^9Beg.s. direct capture reaction at energies of astrophysical interests.     

Determination of the ~(12)C(p, γ)~(13)N reaction rates fromthe ~(12)C(~7Li,~6He)~(13)N reaction

The angular distribution of the 12C(7Li,6He)13N reaction at E(7Li) = 44.0 MeV was measured at the HI-13 tandem accelerator of Beijing, China. The asymptotic normalization coefficient (ANC) of 13N → 12C + p was derived to be (1.64 ± 0.11) fm-1/2 through the distorted wave Born approximation (DWBA) analysis. The ANC was then used to deduce the astrophysical S (E) factors and reaction rates for the 12C(p,γ)13N direct capture reaction at energies of astrophysical relevance.     

Search for the Halo Effect in the ^1H（^6He,^6Li）n Reaction

The angular distributions of the charge exchange reaction ^1H(^6He,^6Li)n were measured in reverse kinematics with a secondary ^6He beam at the energy of 4.17 A MeV.The data were analysed in the context of a microscopic calculation.It is shown that both the ground state of ^6He and the second excited state of ^6Li(3.563MeV,0^ ) have a halo structure.     

Measurement of Angular Distribution for the ^8Li（p,d）^7Li Reaction

The ^8Li（p, d）^7 Li reaction plays an important role in the inhomogeneous Big Bang nucleosynthesis and in the seed-nuclide production phase for the r-process. For the first time, its angular distribution at backward angles was measured in inverse kinematics at Ec.m.=4.0 MeV by using an ^8Li secondary beam. The result of measurement includes the contributions of ^8Li（p, d0）^7Li and ^8Li（p, d1）^7Li^＊. The ^8Li（p, d0）^7Li component is estimated to be 40%-58% in the mixture angular distribution by analysing the measured result.     

Determination of astrophysical ~7Be(p,γ)~8B reaction rates from the ~7Li(d,p)~8Li reaction

The7Be(p,γ)8B reaction plays a central role not only in the evaluation of solar neutrino fluxes but also in the evolution of the first stars.Study of this reaction requires the asymptotic normalization coefficient(ANC) for the virtual decay8 Bg.s.→7Be + p.By using the charge symmetry relation,we obtain this proton ANC with the single neutron ANC of8 Lig.s.→7Li + n,which is determined with the distorted wave Born approximation(DWBA) and adiabatic distorted wave approximation(ADWA) analysis of the7Li(d,p)8Li angular distribution.The astrophysical S-factors and reaction rates of the direct capture process in the7Be(p,γ)8B reaction are further deduced at energies of astrophysical relevance.The astrophysical S-factor at zero energy for direct capture,S17(0),is derived to be(19.9±3.5) e V b in good agreement with the most recent recommended value.The contributions of the1+and 3+resonances to the S-factor and reaction rate are also evaluated.The present result demonstrates that the direct capture dominates the7Be(p,γ)8B reaction in the whole temperature range.This work provides an independent examination to the current results of the7Be(p,γ)8B reaction.     

试用特洛伊木马方法研究天体核反应9Be（p，α）6Li

为克服低能带电粒子核反应截面直接测量中所遇到的库仑位垒和电子屏蔽效应带来的困难，试用基于准自由反应机制的特洛伊木马方法，在意大利南部国家核物理实验室的15MV串列加速器上，通过^2H（^9Be，α^6Li）n核反应对^9Be（p，α）^6Li在低能区（Ecm=0-1000kev）的裸核反应截面做了间接测量，并将测量结果与直接测量数据进行了比较。The beryllium abundance acts as a key role for understanding the inhomogeneous Big Bang nucleosynthesis. In order to measure the ^9Be（p, α）^6Li bare nucleus cross section and S（E） factor at astrophysical energies, the Trojan Horse Method （THM） can be applied. The main feature of the method is that it allows to extract the energy dependence for the astrophysical S（E） factor of bare nuclei at very low energies without any extrapolation, by measuring the cross section of an appropriate three body process. Thus the ^9Be （p,α）^6Li has been studied by means of the THM applied to the ^2H（^9Be,α^6Li）n at INFN-LNS, Catania, Italy. The two body reaction cross section has been studied in the energy range of Ecm=0-1 000 keV. Preliminary results are discussed and a comparison with direct data is made.     

原子能院的核天体物理研究和串列升级工程进展(英文)

在北京串列实验室建立了次级束流实验装置 ,用于放射性核束物理和核天体物理研究 .先后开展了7Be(d ,n) 8B ,11C(d ,n) 12 N ,8Li(d ,p) 9Li和6 He(p ,n) 6 Li核天体物理重要反应的研究 .介绍了串列加速器升级工程的进展情况 .该工程在现有串列加速器的基础上 ,将建立 10 0MeV/ 2 0 0 μA的质子回旋加速器、在线同位素分离器和超导加速段 .在此装置上 ,将可以产生质量数最高为 12 0 ,强度最高为 10 9particles/s的放射性束流 . A secondary beam line (GIRAFFE) at the Beijing Tandem accelerator lab was constructed for yielding low energy secondary beams. The current progress on the study of nuclear astrophysics and nuclear structure is presented. Up to now, We have carried out measurement of~(7)Be(d, n)~( 8)B,~(11)C(d, n)~(12)N,~(8)Li(d, p)~(9)Li, and~(6)He(p, n)~(6)Li reactions. The proposed Beijing radioactive nuclear beam facility (BRIF ) and its current R&D progress are briefly introduced. This facility is based on...     

A density functional theory study on size-dependent structures,stabilities,and electronic properties of bimetallic M_nAg_m(M=Na,Li;n + m≤7) clusters

The equilibrium geometries,relative stabilities,and electronic properties of Mn Agm(M=Na,Li;n + m ≤ 7) as well as pure Ag n,Na n,Li n(n ≤ 7) clusters are systematically investigated by means of the density functional theory.The optimized geometries reveal that for 2 ≤ n ≤ 7,there are significant similarities in geometry among pure Ag n,Na n,and Li n clusters,and the transitions from planar to three-dimensional configurations occur at n = 7,7,and 6,respectively.In contrast,the first three-dimensional(3D) structures are observed at n + m = 5 for both Na n Ag m and Li n Ag m clusters.When n + m ≥ 5,a striking feature is that the trigonal bipyramid becomes the main subunit of Li n Ag m.Furthermore,dramatic odd-even alternative behaviours are obtained in the fragmentation energies,secondorder difference energies,highest occupied and lowest unoccupied molecular orbital energy gaps,and chemical hardness for both pure and doped clusters.The analytic results exhibit that clusters with an even electronic configuration(2,4,6) possess the weakest chemical reactivity and more enhanced stability.     

Measurement of ^2H（^8Li, ^9Be）n Reaction Relevant to Primordial Nucleosynthesis

The angular distribution of the ^2H（^8Li, ^9Be）n （ground state） reaction, important to primordial nucleosynthesis in the inhomogeneous model, has been measured at E = 8.1 MeV using a secondary ^8Li beam. Cross section of this reaction was determined to be 9.0 4±3.4 mb. According to the cross section, the astrophysical S-factor was calculated to be 272 4±103 keV b. It is shown that ^2H（8^Li, ^9Be）n （ground state） reaction is important for creating 9Be, but less important for destroying aLl in primordial nucleosynthesis.     

Neutron spectroscopic factors in 9Li from 2H(8Li,p)9Li

We have studied the 2H(8Li,p)9Li reaction to obtain information on the spins, parities, and single-neutron spectroscopic factors for states in 9Li, using a radioactive 8Li beam. The deduced properties of the lowest three states are compared to the predictions of a number of calculations for the structure of 9Li. The results of ab initio quantum Monte Carlo calculations are in good agreement with the observed properties.     

Ionic Debye Screening in Dense Liquid Plasmas Observed for Li+p,d Reactions with Liquid Li Target

Thick target yields of a particles emitted in the ~6Li(d,a)~4 He and ~7Li(p,a)~4 He reactions were measured for Li target in the solid and liquid phase.Observed reaction rates for the liquid Li are always larger than those for the solid.This suggests that the stopping power of hydrogen ion in the liquid Li metal might be smaller than in the solid.Using the empirically obtained stopping power for the liquid Li,we have deduced the screening potentials of the Li+p and Li+d reactions in both phases.The deduced screening potential for the liquid Li is about 500 eV larger than for the solid.This difference is attributed to the effect of liquefied Li~+ ions.It is concluded that the ionic screening is much stronger than the electronic screening in a low-temperature dense plasmas.     

Quadrupole interaction of8Li and9Li in LiNbO3 and the quadrupole moment of9Li

The quadrupole interaction of nuclear spin polarized⁸Li (I=2) and⁹Li (I=3/2) in LiNbO₃ has been studied at room temperature. The polarization was achieved by optical pumping of a fast atomic beam with circularly polarized laser light. The atoms were implanted into a hexagonal LiNbO₃ single crystal and the quadrupole splitting ofβ-NMR spectra was measured. A ratio of ¦Q(⁹Li)/Q(⁸Li)¦=0.88(4) for the nuclear quadrupole moments was deduced, yielding a new value of ¦Q(⁹Li)¦=25.3 (9) mb for the quadrupole moment of⁹Li.     

New mass value for 7Li

A high-accuracy mass measurement of 7Li was performed with the SMILETRAP Penning-trap mass spectrometer via a cyclotron frequency comparison of 7Li3+ and H2+. A new atomic-mass value of 7Li has been determined to be 7.016 003 425 6(45) u with a relative uncertainty of 0.63 ppb. It has uncovered a discrepancy as large as 14sigma (1.1 microu) deviation relative to the literature value given in the Atomic-Mass Evaluation AME 2003. The importance of the improved and revised 7Li mass value, for calibration purposes in nuclear-charge radii and atomic-mass measurements of the neutron halos 9Li and 11Li, is discussed.     

Ionic Pathways in Li13Si4 investigated by 6Li and 7Li solid state NMR experiments

Local environments and dynamics of lithium ions in the binary lithium silicide Li₁₃Si₄ have been studied by ⁶Li MAS-NMR, ⁷Li spin-lattice relaxation time and site-resolved ⁷Li 2D exchange NMR measurements as a function of mixing time. Variable temperature experiments result in distinct differences in activation energies characterizing the transfer rates between the different lithium sites. Based on this information, a comprehensive picture of the preferred ionic transfer pathways in this silicide has been developed. With respect to local mobility, the results of the present study suggests the ordering Li6/Li7>Li5>Li1>Li4 >Li2/Li3. Mobility within the z=0.5 plane is distinctly higher than within the z=0 plane, and the ionic transfer between the planes is most facile via Li1/Li5 exchange. The lithium ionic mobility can be rationalized on the basis of the type of the coordinating silicide anions and the lithium-lithium distances within the structure. Lithium ions strongly interacting with the isolated Si⁴⁻ anions have distinctly lower mobility than those the coordination of which is dominated by Si₂⁶⁻ dumbbells.     

Li修饰的C$lt;sub$gt;6$lt;/sub$gt;分子对H$lt;sub$gt;2$lt;/sub$gt;O的吸附研究

采用密度泛函理论中的广义梯度近似研究C₆Li吸附H₂O分子并将之进行分解的催化过程. 几何优化发现：Li原子最稳定的吸附位置是位于C 原子顶位上方. 研究表明,第一个H₂O 分子吸附在C₆Li上需要克服1.77 eV的能量势垒,然后分解为H和OH且与Li原子成键. 当吸附第二个H₂O分子时,第二个H₂O分子需要克服1.2 eV的能量势垒分解为H和OH,其中H与Li原子上的H原子结合成H₂,OH则替代Li 原子上的H结合在Li原子上. 因此C₆Li 可以作为催化剂将H₂O分子进行分解得到H₂. 分析可知：C₆Li主要是通过Li原子与H₂O之间形成的偶极矩作用来吸附H₂O 分子,与C₆₀Li₁₂ 的储氢机制类似. 研究结果可为储氢材料的制备提供一个新的思路. 关键词： 6')" href="#">C₆ Li 2O')" href="#">H₂O 密度泛函理论     

Reaction rate of8Li(d,t)7Li

The astrophysical S(E) factor of⁸Li(d,t)⁷Li has been deduced from available data of the inverse reaction⁷Li(t,d)⁸ Li and is consistent with data of direct measurements in the overlapping energy range. The deduced reaction rate at T₉=1 is about an order of magnitude higher than assumed previously.     

锂分子31Πg里德堡态的光谱研究

我们用脉冲光学-光学双共振荧光激发谱(OODR),测量了在35 500～38 000 cm-1能量范围内的里德堡态,观察到7Li231Πg态的10个振动能级.本文对观测的31Пg态的146条激发谱线进行了归属,得到了新的Dunham常数,RKR势能曲线以及A1Σ+u到31Πg态跃迁的夫兰克-康登因子,并且讨论了31Πg态的双重分裂以及与附近里德堡态F(4)1Σ+g,51Σ+g,61Σ+g和G(2)1Πg的微扰.发现在我们的实验精度下(0.2 cm-1) 31Πg态的双重分裂可以忽略.     

Very light neutron-rich nuclei studied via the (6Li, 8B) reaction

Results from investigations of the $\text{T}{}_{\mathrm{z}}\text{=}\text{3}\text{2}$ nuclei ⁵H, ⁷He and ⁹Li and of the T = 1 nuclide ⁴H employing the (⁶Li, ⁸B) reaction at 80 and 93 MeV are presented. In ⁹Li the locations of several low-lying Ip shell levels are indicated; in ⁷He and ⁴H the ground states are clearly observed. No evidence is found for the formation of a narrow ⁵H ground state.     

Li2基态结合能的MACQM计算

本文采用改进的排列通道量子力学方法(MACQM),对Li2基态势能曲线进行了计算,结果表明:在核间距R=5.05a0处,能量有极小值-14.88937a.u,由此得到Li2基态结合能为0.0333a.u,所得结果与实验值符合得很好.