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.     

Interaction of loosely bound radioactive 7Be and stable 7Li with 9Be

Quasielastic scattering angular distributions have been measured for the ⁷Be + ⁹Be system at E _lab = 17 , 19 and 21MeV in the angular range $ \theta_{{cm}}^{}$ = 24^° - 57^° . An optical model (OM) analysis of these data has been carried out in order to extract optical potential parameters and reaction cross-sections. One-proton stripping cross-sections were also measured for this system at E _lab = 19 and 21MeV. These transfer angular-distribution data were compared with the finite-range distorted-wave Born approximation (FRDWBA) calculations. For the ⁷Li + ⁹Be system quasielastic scattering angular distributions were measured and emitted light charged particles were detected at E _lab = 15.75 , 24.00 and 30.00MeV in the angular range $ \theta_{{cm}}^{}$ = 7^° - 70^° . Fusion cross-sections were obtained by reproducing the measured $ \alpha$ -evaporation spectra from the compound nucleus at backward angles with the statistical model calculations. The ratios of the experimental fusion cross-sections to the total reaction cross-sections (obtained from OM analysis) were found to be small. This result suggests that the break-up process has a strong influence on the fusion process leading to a reduction in the fusion cross-section.     

Inorganic solid Li ion conductors: An overview

This short review presents the state-of-the-art knowledge on crystalline, composite and amorphous inorganic solid lithium ion conductors, which are of interest as potential solid electrolytes in lithium batteries and might replace the currently used polymeric lithium ion conductors. The discussion of crystalline Li ion conductors includes perovskite-type Lithium Lanthanum Titanates, NASICON-type, LiSICON- and Thio-LiSICON-type Li ion conductors, as well as garnet-type Li ion conducting oxides. The part on composite Li ion conductors discusses materials containing oxides and mesoporous oxides. In the amorphous Li ion conductor part, mechanical attrition of Li compounds, oxide and sulfide-based glasses as well as LIPON and related systems are presented.     

Comparison of 7Li , 7Be + 9Be elastic scattering in the coupled-reaction-channels approach

The data for the ⁷Li + ⁹Be and ⁷Be + ⁹Be elastic scattering at the energies E _lab(⁷Li) = 15.75 , 24, 30, 34, 63 and 130MeV and E _lab(⁷Be) = 17 , 19 and 21MeV were analyzed within the optical model and coupled-reaction-channels method. The elastic and inelastic scattering, reorientation of ⁷Li , ⁷Be and ⁹Be as well as most important transfer reactions were included in the coupled-channels scheme. The resulting ⁷Li and ⁷Be potentials are very similar and have the same energy dependence. The real potential for recently derived ⁸Be + ⁹Be scattering potentials is very similar to that for ⁷Li , ⁷Be but the imaginary part of the ⁸Be one has a much greater strength at longer range.     

Reaction efficiencies in nucleon channels for 7Li and 9Be nuclei

Reaction cross sections of the radiative capture of nucleons ⁶Li(n, γ)⁷Li, ⁶He(p, γ)⁷Li, and ⁸Li(p, γ)⁹Be in the region of low astrophysical energies are calculated using the dynamic potential cluster model. The results are compared to the available experimental and theoretical data. The yields of these reactions are also calculated, based on the established theoretical results.     

Lithium superionic conductors Li3InBr6 and LiInBr4 studied by 7Li, 115In NMR

Li₃InBr₆ undergoes a phase transition to a superionic phase at 314 K associated with a steep increase of the conductivity (σ = 4 × 10^− 3 Scm^− 1 at 330 K). This superionic phase is isomorphous with Li₃InCl₆ in which a positional disorder at the In³⁺ site is introduced. A pseudo cubic-close-packing of the bromide ions is formed in this phase. On the other hand, a new superionic phase of LiInBr₄ was found above ca 315 K and its structure was confirmed to be a defect spinel. The dynamic properties of the cations in these two superionic phases were investigated by ⁷Li and ¹¹⁵In NMR spectroscopy.     

NMR studies of cation transport in the crystalline ion conductors MCF3SO3 (M = Li,Na) and Li7TaO6

In this contribution we present studies on the mechanism of ion transport in crystalline solid electrolytes employing a range of different solid state nuclear magnetic resonance (NMR) experiments. The first part is devoted to the elucidation of a possible correlation of cation transport and anion reorientation in the dynamically disordered rotor phases of alkali trifluoromethane sulfonates MCF₃SO₃ (M = Li, Na) employing ⁷Li, ¹³C, ¹⁷O and ²³Na NMR line shape analysis, whereas the second part focuses on the tracking of cation diffusion pathways in the hexaoxometalate Li₇TaO₆ utilizing ⁶Li 1D and 2D exchange MAS NMR approaches.     

6Li and 7li solid-state NMR spectroscopy of nitrogen ceramic phases

Two nitrogen ceramic phases, the oxynitride LiSiON and the nitride LiSi2N3, have been studied by 6Li and 7Li NMR. Magic angle spinning (MAS) NMR experiments have been carried out at two magnetic field strengths (7.05 and 14.1 T). The spectra give evidence of the relative effects of the quadrupolar and chemical shift interactions. The electric field gradient tensor of both phases has been determined accurately by iterative fitting of the 6Li and 7Li MAS NMR line shapes at the two magnetic field strengths. Due to the fact that for 7Li the quadrupolar interaction is much larger than the chemical shift interaction, it is shown that neither the small chemical shift anisotropy nor the relative orientation of the two interaction tensors can be determined accurately by 7Li MAS NMR. For 6Li, the two interactions are comparable and the value of these parameters obtained from the fits of the 6Li experimental MAS line shapes are therefore much more reliable.     

7Li quasi-free scattering off the α-cluster in 9Be nucleus

Spectra of coincident charged particles from the reactions induced by a 52 MeV ⁷Li beam incident on a beryllium target were measured. Strong contributions of the ⁷Li quasi-free scattering off the α-cluster in ⁹Be nucleus were observed. This observation supports the conclusions from the study of complete fusion of weakly bound light nuclei at low energies that the “fragility” of the nuclei makes their fusion less probable. Received: 1 June 1998     

Stimulated-Echo NMR Spectroscopy of Be and Li in Solids: Method and Application to Ion Conductors

The generation of pure quadrupolar stimulated-echo spectra is successfully demonstrated for the spin- probe ⁹Be in a single crystal of triglycine fluoberyllate. This solid exhibits a paraelectric-to-ferroelectric phase transition. From experiments carried out for various mixing times no indications for a slow soft mode could be detected in this crystal. Then ion conducting lithium metal phosphates were studied using ⁷Li, another spin- probe which allows for a non-selective excitation of the entire NMR spectrum. In the indium and the scandium phosphates ultra-slow Li hopping processes could be detected directly via the stimulated-echo technique in a time range of up to four orders of magnitude. Due to the relatively large gyromagnetic ratio and thus strong dipolar interactions of ⁷Li no pure quadrupolar echoes could be generated. However, from a variation of the evolution times the quadrupolar effects could be separated from the dipolar ones. Finally, the differences in the ion hopping times of lithium indium phosphate and of lithium scandium phosphate are briefly discussed.     

Reflectivity measurements of superionic conductors for Li ion secondary battery materials

The reflection measurements of superionic conductors LiCoO₂ and Li_1-xCoO₂, which are already in use for the positive electrode material of 4 V rechargeable lithium batteries, have been performed in the millimeter wave region from 6 to 60 cm⁻¹ using the electron storage ring facilities of Institute of Molecular Science in Okazaki. The increase of the reflectivity has been observed in the low wavenumber region below 10 cm^-1 above 300 K in Li_1-xCoO₂ for the first time, while the reflectivity of LiCoO₂ has almost the constant value in all observed temperature region between 77 to 380 K. The results will be discussed in connection with our previous results of LiNiO₂.     

1-D and 2-D NMR of broad-line solids: an application to quasicrystals

Nuclear magnetic resonance (NMR) techniques for measuring one-dimensional absorption spectra and two-dimensional exchange spectra of solids with extremely inhomogeneously broadened lines are discussed. Among various “broad-line” solids, quasicrystals represent alloys of metallic elements, the structures of which include “forbidden” symmetry elements. NMR absorption lines of quasicrystals exhibit a strong electric-quadrupole-induced inhomogeneous broadening that originates from the lack of translational periodicity of the otherwise perfectly long-range-ordered quasiperiodic lattice. Recording an NMR spectrum of a quasicrystalline sample requires a magnetic field-sweep technique. The two-dimensional exchange experiment on quasicrystals can be performed on selectively excited portions of the NMR spectrum only. Due to the off-resonance effects in a selective excitation, the use of a simple three-pulse stimulated-echo exchange sequence is preferred. The²⁷Al spectra of the Al-Pd-Mn and Al-Pd-Re families show interesting features like temperature-dependent frequency shifts and exchange effects due to atomic motion.     

Hole traps and thermoluminescence in Li2B4O7:Be

A trapped-hole centre with a high thermal stability is studied in Li₂B₄O₇:Be. EPR spectrum demonstrates a hyperfine splitting due to interaction of the trapped hole with a ⁹Be nucleus. The hole is trapped at the common vertex (bridging oxygen) of two adjacent BO₄ tetrahedra when Be²⁺ substitutes for B³⁺ in one of them. The centre is stable up to ≈500 K. The high-temperature thermoluminescence peak at 510–575 K occurs when the released holes recombine with trapped electrons. This peak shows an ultraviolet exciton-like luminescence band and also luminescence bands of casual impurities.     

Applications of (7)Li NMR in biomedicine

The applications of (7)Li NMR spectroscopy and imaging in biology and experimental medicine have been progressing steadily. The interest derives primarily from the clinical use of Li salts to treat mania and manic-depressive illness. One area of investigation is ionic transport across the cellular membrane and compartmentation, so as to elucidate the mechanism(s) of therapeutic action and toxicity in clinical practice. The second is the development of a noninvasive, in vivo analytical tool to measure brain Li concentrations in humans, both as an adjunct to treatment and as a mechanistic probe. Here we review progress to date in this area.     

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.     

Surface investigation of solids by the statical method of secondary ion mass spectroscopy (SIMS)

The physical and chemical properties of a solid surface are determined by its uppermost monolayers. Besides other methods like Auger electron spectroscopy (AES) and X-ray electron spectroscopy (ESCA) for example, the chemical composition of these uppermost monolayers can be investigated by the statical method of secondary ion mass spectroscopy (SIMS). In this method a relatively large target area (0.1 cm²) is bombarded with a small primary ion current density (10^?9 A cm^?2). Thus a sputtering time of several hours is achieved for an individual monolayer. A mass analysis of the emitted positive and negative secondary ions gives information about the chemical composition of the uppermost monomolecular layer of the bombarded surface. Important features of SIMS are: detection of chemical compounds; isotope sensitivity; detection of hydrogen and its compounds ; depth resolution in the range of a single monolayer ; low detection limits (< 10^?6 monolayer or < 10^?14 g) for many elements and compounds.The capacity of this method is demonstrated using as examples the initial surface oxidation of metals and semiconductors and adsorption phenomena on clean metal surfaces. In some special cases additional information on the chemical composition of the uppermost monolayer can be obtained by the electron induced ion emission from the surface.