The photodisintegration of6Li and7Li

The photodisintegration of the stable Lithium isotopes has been investigated by spectroscopy of the emitted charged particles using the Giessen bremsstrahlung facility. Protons, deuterons, tritons,³He and alpha particles were detected and identified up to 20MeV particle energy. Angular distributions were measured using γ-ray energies up toE _γ =50 MeV. They are compared with theoretical predictions and with other experiments. A remarkable low (γ, t)-cross section was found for both isotopes in disagreement to previous measurements using virtual photons. Coincidence measurements between the emitted particles were performed in order to study the manybody-breakups of⁷Li.     

同位素7Li和6Li的性质殊异

本文研究了同位素7 Li和6 Li在几个方面的性质差异．用相对论量子力学计算指出,6 Li的电子能级比7 Li的能级低,同时,对电偶极E （1）和磁偶极M （1）的能级跃迁波长,6 Li的跃迁波长都要比7 Li的长．由于7 Li和6 Li的核自旋的大小不同,可以看出在磁场2万高斯和温度100－20 K之间,7 Li的磁极化比6 Li的约大13倍．7 Li和6 Li的磁极化这种差异,也是一种可能的同位素7 Li／6 Li的分离方法．     

Measurements of elastic scattering for 7Be, 7Li + 9Be systems and fusion cross sections for 7Li + 9Be system

Elastic scattering angular distributions have been measured for ⁷Be + ⁹Be system at E_lab = 17, 19 and 21 MeV in the angular range θ_cm=26^○–58°, and for ⁷Li + ⁹Be system at E_lab= 15.75, 24 and 30 MeV. An optical model (OM) analysis of these data have been carried out. For the ⁷Li + ⁹Be system fusion cross sections were obtained at E_lab = 15.75, 24 and 30 MeV by measuring the α-evaporation spectra from the compound nucleus at backward angles. The measured α-evaporation spectra were reproduced by the statistical model calculations and fusion cross sections were extracted therefrom. The ratios of the experimental fusion cross sections to the total reaction cross sections (obtained form OM analysis) were found to be rather small. This result suggests that break-up process has a strong influence on fusion process leading to a reduction in fusion cross section.     

Isoscalar excitations of7Li

Inelastic scattering of 35 MeV alpha particles from⁷Li was used to induce the five known inelastic excitations. A collective coupled channel analysis yielded deformations for each transition and isoscalar quadrupole reduced transition rates were determined for each. The strong-coupling rotational model was found to agree closely with the results for the states associated with the ground state band, but the higher states are excited mainly by a two-step mechanism.     

Laser-catalyzed production of ultracold molecules: the 6Li+6Li7Li-->homega6Li-6Li+7Li reaction

We show that by using laser catalysis, we can employ translationally cold (Tr approximately 1.75 K) collisions to produce ultracold (0.01 mKhomega(6Li6Li7Li)*(1(4)A')-->homega6Li6Li+7Li reaction in the collinear approximation. Ultracold 6Li6Li product molecules are shown to be produced at an extraordinary yield of up to 99.97%, using moderate laser intensities of I=100 kW/cm(2)-10 MW/cm2.     

Coulombformfaktoren für7Li

Using refined clustermodel wave functions the Coulomb form factors for the elastic scattering of electrons as well as the formfactors for the inelastic scattering leading to the first and second excited states of⁷Li have been calculated.     

Fusion around the barrier for 7Li+12C

Fusion cross-sections for the ⁷Li + ¹²C reaction have been measured at energies above the Coulomb barrier by the direct detection of evaporation residues. The heavy evaporation residues with energies below 3 MeV could not be separated out from the α-particles in the spectrum and hence their contribution was estimated using statistical model calculations. The present work indicates that suppression of fusion cross-sections due to the breakup of ⁷Li may not be significant for ⁷Li + ¹²C reaction at energies around the barrier.     

同位素7Li和6Li 的性质殊异和应用

本文研究了同位素7Li和6Li在几个方面的性质差异。用相对论量子力学计算指出,6Li的电子能级7Li的能级低,同时,对电偶极E（1）和磁偶极M(1)的能级跃迁波长,6Li 的跃迁波长都要比7Li 的长。 非相对论量子力学方法（B3LYP/6-311G**）计算总的核自旋-自旋偶合常数 。由于7Li 和6Li 的核自旋大小不同,当其与其它原子偶合时所导致的偶合常数的差异, 是一种可能的分离同位素7Li/6Li 的方法的础。可以看出在磁场2万高斯和温度100-20 K之间 ,7Li的磁极化比6Li的约大13 倍。7Li 和6Li 的磁极化这种差异,也是一种可能的同位素7Li/6Li 的分离方法。     

Nuclear-matter radii of 7Be and 7Li and astrophysical S-factors for radiative alpha-capture reactions

The nuclear-matter radii of ⁷Be and ⁷Li measured in high-energy heavy-ion reactions have been calculated and applied to the estimate of astrophysical S-factors for the ³He(α,γ)⁷Be and ³G(α,γ)⁷Li reactions. The absolute S(O) values in the KeV b are constrained to be 0.36<S(0)<0.63 and 0.083<S(0)<015 for the ³He(α,γ)⁷Be and ³H(α,γ)⁷Li reactions, respectively.     

Predissociation induced by ungerade-gerade symmetry breaking in 6Li7Li molecule

In the recent sub-Doppler experiment on the B1Pi(u) state of the Li2 molecule by Bouloufa et al. [J. Chem. Phys. 111, 1926 (1999)], where the dissociation of vibrational levels due to the tunneling through the potential barrier was investigated, several vibrational levels with abnormally large dissociated rates were observed in the case of the 6Li7Li isotopomer. This dynamical effect cannot be explained by tunneling as in the case of 6Li2 or 7Li2. A simple model of coupling between B1Pi(u) and 1(1)Pi(g) states involving the u-g symmetry breaking for 6Li7Li is proposed. Rates of the B1Pi(u) predissociated levels due to this coupling are calculated. A good agreement with the experiment is found.     

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.     

同位素7Li和6Li 的性质殊异和应用

本文研究了同位素7Li和6Li在几个方面的性质差异。用相对论量子力学计算指出,6Li的电子能级7Li的能级低,同时,对电偶极E（1）和磁偶极M(1)的能级跃迁波长,6Li 的跃迁波长都要比7Li 的长。 非相对论量子力学方法（B3LYP/6-311G**）计算总的核自旋-自旋偶合常数 。由于7Li 和6Li 的核自旋大小不同,当其与其它原子偶合时所导致的偶合常数的差异, 是一种可能的分离同位素7Li/6Li 的方法的础。可以看出在磁场2万高斯和温度100-20 K之间 ,7Li的磁极化比6Li的约大13 倍。7Li 和6Li 的磁极化这种差异,也是一种可能的同位素7Li/6Li 的分离方法。     

Metallic Li colloids studied by 7 Li MAS NMR in electron-irradiated LiF

7 Li MAS NMR spectra of 2.5 v MeV electron-irradiated LiF crystals have been measured in a field of 9.4 v T. Besides the resonance line of the ionic compound, a second well-separated spectrum is observed in the region of the Knight shift value for metallic lithium. At room temperature, the latter can be decomposed into two components with different Knight shift and linewidth values. When the temperature is increased, line narrowing takes place at first, indicating shortening of correlation times for self-diffusion, independently in both components. Above 370 v K, both lines broaden and approach each other before collapsing into a single line. The high ppm component disappears after crossing the melting temperature of metallic lithium (454 v K). The two lines are attributed to different types of metallic Li: one to bulk-like metal, the other to Li present initially under pressure and relaxing to the former under thermal treatment.     

Ab initio Monte Carlo shell model calculations for ~7Li and ~9Li low-lying spectra

The low-lying spectra of7 Li and9Li are investigated within an ab initio Monte Carlo Shell Model(MCSM) employing a realistic potential obtained via the Unitary Correlation Operator Method(UCOM). The MCSM calculations in a 4-major-shells model space for the binding energy and mass quadrupole moment of7, 9Li show good convergence when the MCSM dimension reaches 20. The excitation energy of the Jπ= 1/2-state for7 Li and the magnetic moments for7, 9Li ground states in the MCSM with a treatment of spurious center-of-mass motion are close to the experimental data. Correct level ordering of Jπ=3/2-and 1/2-states for7, 9Li can be reproduced due to the inclusion of three-body correlations in the MCSM+UCOM. However, the excitation energy of Jπ=1/2-state for9 Li is not reproduced in the MCSM mainly due to the lack of larger model space.     

The4He(α,p)7Li,7Li*0.478 reaction near threshold

Differential cross sections for the reaction⁴He(α,p)⁷Li,⁷Li^{* 0.478MeV} have been obtained at nine energies between 37 and 43 MeV in the laboratory system. It is shown that these results are consistent with a non zero inelasticity in thel=4 partial wave of the entrance channel. Comparisons with the reaction cross section for the⁴He-α interaction are discussed.     

电池正极材料中Li~+运动特性的~7Li NMR研究

利用变温７ＬｉＮＭＲ实验对Ｌｉ电池正极材料ＬｉＭｎ２Ｏ４和ＬｉＣｏＯ２中Ｌｉ＋的运动特性进行了研究，结果表明，随实验温度的提高，ＬｉＭｎ２Ｏ４的７ＬｉＮＭＲ谱线窄化，表明其中Ｌｉ＋迁移能力增加，而ＬｉＣｏＯ２的谱线无变化．此外随温度提高，ＬｉＭｎ２Ｏ４的７Ｌｉ的Ｔ１变短，而ＬｉＣｏＯ２的Ｔ１变长，产生这种不同变化趋势的原因在于ＬｉＭｎ２Ｏ４和ＬｉＣｏＯ２晶相结构的差异造成其中Ｌｉ＋迁移能力的差别，它们各自的相关时间τｃ使７Ｌｉ核的Ｔ１分别位于Ｔ１－τｃ曲线极小点两侧