Solvent-free methylthiomethyllithium [LiCH2SMe]infinity: solid state structure and thermal decomposition

Solvent-free [LiCH2SMe]infinity forms a layer structure consisting of four- (Li2C2), five- (Li2CS2), and six-membered (Li2C2S2) rings in the solid state; the compound violently explodes upon heating to T=160+/-5 degrees C under an argon atmosphere.     

Continuous wave NMR of submonolayer 3He adsorbed on grafoil

NMR linewidths and magnetic susceptibilities of ³He adsorbed on Grafoil have been measured by a continuous wave technique between 0.40 K to 4.21 K for five fractional monolayer coverages, x, between 0.20 and 0.96. Interpretations in terms of the phases of the submonolayers are presented.     

Synthesis of ternary and quaternary graphite intercalation compounds containing alkali metal cations and diamines

A series of ternary graphite intercalation compounds (GICs) of alkali metal cations (M = Li, Na, K) and diamines [EN (ethylenediamine), 12DAP (1,2-diaminopropane), and DMEDA (N,N-dimethylethylenediamine)] are reported. These include stage 1 and 2 M-EN-GIC (M = Li, d(i) = 0.68-0.84 nm; M = Na, d(i) = 0.68 nm), stage 2 Li-12DAP-GIC (d(i) = 0.83 nm), and stage 1 and 2 Li-DMEDA-GIC (d(i) = 0.91 nm), where d(i) is the gallery height. For M = Li, a perpendicular-to-parallel transition of EN is observed upon evacuation, whereas for M = Na, the EN remains in parallel orientation. Li-12DAP-GIC and Li-DMEDA-GIC contain chelated Li(+) and do not show the perpendicular-to-parallel transition. We also report the quaternary compounds of mixed cations (Li,Na)-12DAP-GIC and mixed amines Na-(EN,12DAP)-GIC, with d(i) values in both cases between those of the ternary end members. (Li,Na)-12DAP-GIC is a solid solution with lattice dimensions dependent on composition, whereas for Na-(EN,12DAP)-GIC, the lattice dimension does not vary with amine content.     

Fabrication and characterization of TEOS-based silica aerogels prepared using rapid supercritical extraction

Silica aerogels were prepared using the precursor tetraethylorthosilicate (TEOS) via a rapid supercritical extraction (RSCE) method. Multiple consistent batches of monolithic TEOS-based aerogels were fabricated via an 8-h RSCE process. Fabricating TEOS-based aerogels with an RSCE method offers some distinct advantages. One advantage is the relative simplicity of the RSCE approach: liquid precursors are mixed and poured into a metal mold in a hydraulic hot-press, where gelation, aging and extraction of liquid from the pores occur. The precursor recipe employs TEOS, ethanol, water, oxalic acid to catalyze hydrolysis, and ammonia to catalyze the subsequent polycondensation reactions. Another advantage is that reaction of TEOS to form sol gels yields ethanol as a byproduct. A process that releases ethanol, rather than methanol (as in tetramethylorthosilicate (TMOS)-based aerogels) may be more appealing for commercial applications, involving scale-up of the process. The significantly lower cost of TEOS, compared to TMOS, is a considerable advantage. The TEOS-based RSCE aerogels are mesoporous and optically translucent, have bulk densities of 0.099(±0.003) g/cm³ and surface areas of 460(±10) m²/g. Signals observed in infrared and Raman spectra of the aerogels are consistent with Si–O framework bonds. Using scanning electron microscopy imaging, the surface morphology of the aerogel samples was imaged at magnifications up to 150 kX.     

Improved calculation of distributions sensitive to the three gluon vertex ine + e −→4-jets using a coherent parton shower simulator

The calculation of hadron distributions ine ⁺ e ^?→4-jets using the 4-parton matrix element diverges unless cuts are imposed on the parton phase space. Experimentally cuts can be applied only on the hadron spectrum and not at the 4-parton level. Test observables for the three gluon vertex relying on jet-jet angular correlations are found to be particularly sensitive to these parton cuts. The contribution from the parton phase space below the cut region is calculated to modified logarithmic approximation accuracy using a Monte Carlo simulator HERWIG and is found to be of order 45%. This modifies the predictions of the tests so that differences between QCD and ‘QED’ are diminished significantly. A tagging method based on the average energy of particles in a jet is found to be best at identifying both gluon jets with a possible 9:1 success to failure ratio and it allows the presence of the three gluon vertex to be verified.     

On the crystallization of two-dimensional electron system in strong magnetic field

The possibility of the two-dimensional electron crystallization in the strong magnetic field is discussed by comparison between electron free energies in liquid and crystal states. The electron free energy in the liquid state is determined in Hartree-Fock approximation, while the correlation phenomena are proved to be negligible. The electron free energy in the crystal state is calculated in the harmonic approximation. The magnetic field is shown to “nonmonotonously” affect the crystal formation. From one hand, an electron crystal may exist in an interval of the strong magnetic field H at rather high density, where that is impossible at H=0. From the other hand, at any density the sufficiently strong field forces electron lattice to melt at finite temperature.