Fast ignition by intense laser-accelerated proton beams

The concept of fast ignition with inertial confinement fusion (ICF) is a way to reduce the energy required for ignition and burn and to maximize the gain produced by a single implosion. Based on recent experimental findings at the PETAWATT laser at Lawrence Livermore National Laboratory, an intense proton beam to achieve fast ignition is proposed. It is produced by direct laser acceleration and focused onto the pellet from the rear side of an irradiated target and can be integrated into a hohlraum for indirect drive ICF.     

Substituent effect on torsional barriers in N,N′-dibenzylhydrazobenzenes.

Substituted hydrazobenzenes were prepared and their barriers to rotation measured by DNMR spectroscopy and correlated with σ^? substituent constants with a reaction constant ?₃₀₀ = ?1.09.     

Image-potential states on stepped Cu (001) surfaces

Image-potential states on Cu (117) and Cu (119) surfaces were studied by means of two-photon photoelectron spectroscopy. The regular array of steps generates a lateral potential on the vicinal surfaces, which modifies the surface-electronic structure. Compared to Cu (001), the band bottom of the n=1 image-potential states shifts by 40 meV to lower binding energy. The periodicity of the step-induced superlattice manifests itself as back-folding of the n=1 and 2 dispersion bands. At the surface Brillouin zone boundary a mini-gap opens with a width of 135 meV for the first image-potential state on Cu (117). On the vicinal surfaces the lifetime of the image-potential states is reduced by a factor of three as compared to Cu (001). This is attributed to a narrowing of the surface-projected bulk-band gap when projected along the [11n] direction. While the dephasing rate of the first image-potential state is close to the decay rate, higher members of the Rydberg-like series show negligible dephasing. Received: 16 October 2001 / Revised version: 9 April 2002 / Published online: 6 June 2002     

The solubility of alkali-metal fluorides in non-aqueous solvents with and without crown ethers, as determined by flame emission spectrometry

The solubilities of LiF, NaF, KF, RbF and CsF in acetonitrile, acetone, tetrahydrofuran, dimethylformamide, benzene and cyclohexane have been determined with and without a crown ether (usually 0.1 M 18-crown-6) present. Flame emission spectrometry was the determination method. Three procedures, selected according to the miscibility of the solvent with water, and the solubility of the fluoride, are described. Samples, standards and blanks were matrix-matched. The precision varied between 1 and 10% RSD. Although extensive drying procedures were applied, moisture present in the solvents and salts had some effect on the results.     

Resonant Raman scattering in polyacetylene under hydrostatic pressure

The results of resonant Raman scattering experiments on trans-poly-acetylene under hydrostatic pressure are reported. The measurements were performed in a diamond anvil cell. The spectra could be measured up to 44 kbar. The pressure dependence of the 1295 cm^-1 line was measured in a sapphire cell up to 17 kbar. The results show that the changes in the phonon frequencies are very small. By comparing the pressure dependence of the Raman bands with their dependence on the photon energy of the exciting laser line it is possible to determine the pressure variation of the electronic energy gap. The results are consistent with previous measurements of the absorption spectrum under hydrostatic pressure which were carried out up to 13.5 kbar. The gap is found to decrease rapidly with pressure but the decrease tends to saturate at high pressures. The results are consistent with a model in which chain-chain interaction plays a dominant role.     

Zur Anwendung von NMR-Verschiebungsreagenzien: Die Komplexbildungskonstante als Strukturparameter

The determination of the structure of a tetra-tert-butylfluoren-9-ol, using the complex formation constants of some known tert-butylfluorenols with Eu(fod)₃, is described.