The kinetics of the gas-phase reaction between iodine and phenylsilane and the bond dissociation energy D(C6H5SiH2?H)

The title reaction has been investigated in the temperature range of 490-573 K. Initial reactant pressures were varied in the range of 0.2-5.2 torr (I₂) and 2-20 torr (C₆H₅SiH₃). The rate of iodine consumption, monitored spectrophotometrically, was found to obey both by initial rate and integrated equation fitting procedures. The effect of added initial HI conformed to this expression. The data are consistent with a conventional I-atom propagated chain reaction, and for the step the rate constant is given by From this is derived the bond dissociation energy value C₆H₅SiH₂? H = 374 kJ/mol(88 kcal/mol). A comparison with other Si? H dissociation energy values indicates that the “silabenzyl” stabilization energy is small, ≈7 kJ/mol.     

Switching valves for use in multi-column gas chromatography

Two switching valves for use in multi-column and frontal gas chromatography are described. Constructional and operational details are given and examples of use are quoted.     

Nature of the band gap of In2O3 revealed by first-principles calculations and x-ray spectroscopy

Bulk and surface sensitive x-ray spectroscopic techniques are applied in tandem to show that the valence band edge for In2O3 is found significantly closer to the bottom of the conduction band than expected on the basis of the widely quoted bulk band gap of 3.75 eV. First-principles theory shows that the upper valence bands of In2O3 exhibit a small dispersion and the conduction band minimum is positioned at Gamma. However, direct optical transitions give a minimal dipole intensity until 0.8 eV below the valence band maximum. The results set an upper limit on the fundamental band gap of 2.9 eV.     

Temperature distribution on an isoflux surface cooled by an impinging liquid jet with a 40° Wall Jet Swirl Generator

Graphical Abstract  

     

Characterisation of a 3 nanosecond pulsed atmospheric pressure argon microplasma

This study details the generation and characterisation of a 3 nanosecond pulsed atmospheric pressure argon microdischarge, and provides a comparison with a comparable DC microplasma. There is a growing interest in short pulsed excitation of microplasmas as a gateway to access highly non-equilibrium discharge chemistry that is inaccessible using other excitation mechanisms. By combining time-resolved electrical and optical diagnostics the repetitive 3 nanosecond pulses considered in this study are shown to produce a highly transient plasma with a peak dissipated power above 160 kW and electron densities in excess of 10¹⁷ cm^-3. During the afterglow period electrons rapidly cool below the excitation threshold suggesting emission from excited argon neutrals should also diminish rapidly. However, argon emissions are observed for several microseconds after each applied pulse, far in excess of their radiative lifetimes. Potential repopulation mechanisms are considered and it is concluded that electron-ion recombination is the most likely repopulation process.     

Quantitative prediction of high field,short pulse behaviour of amorphous semiconductors

Two sets of carriers reveal themselves in amorphous chalcogenide thin films subjected to high electric fields. The application to the samples of short high field pulses, in the range of tens of nanoseconds, shows the same conduction processes present as when applying pulses whose lengths are nearly a million times longer. The coupled carrier equations have been combined with a band model which assigns the carriers respectively to localized hopping or trapping states near the band edge and to extended states near the mobility edge to explain the conduction behaviour. The success of this theory, found earlier with long pulse measurements, continues with short pulse experiments. The theory is substantially free of adjustable parameters and gives numerical and functional agreement in 10 specific cases when applied to 7 experimental phenomena discovered with the short pulse experiments.