Halocarbon and arene coordination of lithium(I) in (1‐anilino‐3‐phenyl­imino­propenyl)chloro(methyl)­aluminium bis{[tetrakis(pentafluoro­phenyl)­borato]­lithium} benzene solvate

The crystal structure of the title compound, [AlCl(CH₃)‐(C₁₅H₁₃N₂)]­[Li(C₂₄BF₂₀)]₂­·C₆H₆, is reported. The unusual coordination features of the lithium(I) cation, including Li‐atom coordination to six organohalogen atoms and the shortest Li—F(C) distances so far observed, are discussed.     

[Hydroxy­tris­(penta­fluoro­phenyl)­borato‐O][N‐iso­propyl‐2‐(iso­propyl­amino)­troponiminato‐N]­methyl­indium(III)

The title complex, [In(CH₃)(C₁₈HBF₁₅O)(C₁₃H₁₉N₂)], crystallizes as an ion pair linked by a μ‐hydro­xo bridge. There are two independent mol­ecules in the asymmetric unit that exhibit essentially identical metric parameters, but different conformations.     

Acoustical criteria for concert hall stages

A survey of values of the inversion index (II) in a number of concert halls reveals large variations. Extreme values occur for stages of obviously quite different properties.Recent investigations have concentrated on the energy balance between direct sound energy and early reflection energy for a number of concert hall stages.Some numerical results, together with the corresponding reflectograms, are commented upon.     

Über das Verhältnis der Theorie der Elementarlänge zur Quantentheorie. II

The idea put forward in I that also such algebras which do not fulfil the axiom of powerassociativity may allow in some cases physical interpretation, is illustrated by a mathematical model showing properties similar to the Cartesian coordinates of a particle.     

Temporary anions of the fluoroethylenes

Electron transmission spectroscopy is employed to measure the gas phase electron affinities of the fluoroethylenes. Fluorination is found to destabilize the π* anions with respect to that of ethylene. The role of bond length changes as well as inductive and resonance effects is examined.     

Laser-induced fluorescence measurements and modeling of absolute CH concentrations in strained laminar methane/air diffusion flames

We have applied linear laser-induced fluorescence to obtain spatially resolved profiles of CH radicals in laminar methane/air and methane/nitric oxide/air counterflow diffusion flames at atmospheric pressure. Excitation and detection of transitions in the A–X band and calibrating the optical detection efficiency via Rayleigh scattering allowed the determination of absolute radical concentrations. Flames at strain rates from 59 to 269 s⁻¹ were studied to characterize the strain rate dependence of the CH concentration. The work shows that CH concentrations increase with increasing strain rate. Comparisons have been made with predicted CH levels obtained using two different chemical kinetic mechanisms (Lindstedt et al. and GRI-Mech. 3.0). Computed concentrations are shown to be in good agreement with experimental data. It was furthermore found that the addition of up to 600 ppm NO to the fuel did not have a measurable effect on the CH radical concentration. This is also in agreement with predictions from both mechanisms. The current work has shown that measurements of absolute CH radical concentrations are possible in non-premixed flames without the need for spatial temperature or quenching corrections.     

Extended Hückel calculations on the conformation and structure of thymine photodimers

Extended Hückel calculations have been performed for the structure of C₅-C₆ dihydrouracil and thymine and for the uracil and thymine photodimers. The results indicate, in agreement with experiment, that the most stable conformation of the dihydropyrimidines should be the half-chair one. The preferred conformations of the dimers should correspond to planar bases forming an angle of 120° with the cyclobutane ring. The most stable dimers, per se, appear to be the trans-anti and the trans-syn ones in the case of uracil and the cis-anti and the trans-anti ones in the case of thymine. Other factors than inherent stability must play a decisive role in the production of the dimers under specific conditions. When a semi-empirical reduction is carried out upon their absolute values the dipole moments predicted for the different conformers of the thymine dimer agree very satisfactorily with experiment.     

Efficient compression of femtosecond pulses by stimulated Raman scattering

Femtosecond pulses at 496 nm were Raman-shifted in methane with 20% efficiency. The pulse duration could be reduced up to 6.5 times from 560 fs at the fundamental to 85 fs at the Stokes frequency (580nm), which is the shortest pulse duration generated in this way. It was shown experimentally that chirped-pulse Raman scattering avoids the limitations arising from self-phase modulation.