Bruno Reimann

This chapter aims at a description of the application and proper use of reference materials in gas analysis. It is not a treatise on gas analysis; there are numerous and excellent textbooks available dealing with that subject ([7.1] and [7.2], to name just two). Here, gas analytical techniques will only be mentioned if relevant to the use of gaseou...

The reactions of O( 3 P) atoms with the silanes Me 4−n SiH n (n=1-4) have been investigated at room temperature in a discharge flow system with mass spectrometric detection and also in stationary photolysis experiments. Analysis of the end products provided conclusive evidence that the only primary process occurring in each case was the abstraction...

The absorption spectra of the trimethyl—, triethyl— and tri—n—propylsilyl radicals, generated by the mercury—sensitized photolysis of the corresponding silanes, were observed in a chemical modulation experiment. The absorption cross-section of the trimethylsilyl radical was measured, the value obtained being σ (260 nm, base e) = 3 × 10−17 cm2 per m...

The reaction system H + (CH3)4Si ⇄ H2 + (CH3)3SiCH2 (1, -1) has been studied in pulsed photolysis experiments in the temperature range 425-570 K. H atoms were generated by Hg-sensitized photolysis of H2, and were monitored by Lyman-α absorption. The rate constant for the forward reaction, measured at an H2 pressure of 133 Pa, is given by the expres...

Arrhenius parameters have been measured for H abstraction by H atoms from the Si—H bond in a number of differently substituted silanes and disilanes. In the case of silane and trimethylsilane kinetic isotope effects have also been determined. The available data on the reactions studied are collated and evaluated, and the trends which emerge are dis...

Fluorescence experiments with beryllium and atomic oxygen are described. VUV-radiation generated by high-order anti-Stokes Raman scattering in molecular hydrogen is used to excite resonance transitions at 235 nm and 166 nm (Be) and at 130 nm (O). The results show that the available VUV power and the spectral properties allow applications of this VU...

Employing static irradiation with GC product analysis and using NO, O2, and trans-1,3-pentadiene as scavengers and CO2 as a buffer gas it is shown that roughly 25% of the total 1,3-acetyl shift (1,3-AS) (I) (II) proceeds in an orbital-symmetry-allowed concerted fashion from the first excited singlet state and not via radical pairs.

The 1,3-acetyl shift of the photoexcited β,γ-unsaturated ketone 1,2-dimethylcyclopent-2-enyl methyl ketone has been investigated in the gas phase at room temperature and with 1 bar of CO2 as a buffer gas. Roughly 25% of the total 1,3-acetyl shift reaction is shown to proceed in an orbital-symmetry-allowed concerted fashion from the first excited si...

The reaction of SiH4 with active nitrogen in a discharge-flow system was found to produce strong chemiionization besides the well-known SiN★ and Si★ chemiluminescences. In the presence of a large initial excess of N atoms, both N and SiH4 disappeared completely in the course of the reaction. Addition of as little O2 as 1013 cm−3 was sufficient to q...

The reaction of H atoms with a number of mono-, di-, and trisilanes has been studied with the view of examining the possible occurrence of a homolytic substitution reaction (SH2). Arrhenius parameters for abstraction plus substitution have been determined for the reaction of H atoms with Si2H6, Me3SiSiMe2H, Me3SiSiCl3, Si2Cl6, and Me8Si3. The ratio...

VUV radiation generated by stimulated Raman scattering from H2 and tunable around 130 nm is applied to the detection of atomic oxygen produced in a flow-tube. Concentrations in the range to the detection of atomic oxygen produced in a flow-tube. Concentrations in the range of 1010 to 1011 O-atoms per cm3 lead to fluorescence signals that can easily...

Die Hg(′P,)-sensibilisierte Photolyse von H2/SiH4-Mischungen liefert neben Si,H6 auch Si3H3 und Si4Hm.

The Hg (3P1) sensitized photolysis of an H2/SiH4 mixture not only yields Si2H6 but also Si3H8 and Si4H10. The formation of the latter two products as well as parts of the Si2H6 yield is explained by the decomposition of chemically activated disilane, formed by the combination of two silyl radicals. The activated disilane decomposes mainly into SiH2...

The reaction of hydrogen atoms with hexamethyldisilane has been studied by pulsed, mercury-sensitized photolysis experiments using Lyman α resonance absorption and resonance fluorescence detection of H atoms. At room temperature it proceeds exclusively according to H + (CH3)3SiSi(CH3)3 → (CH3)3SiH + (CH3)3Si (1) with a rate constant k(1) = (3.55 ±...

The reactions of hydrogen atoms with silane and the methylated silanes - with the exception of tetramethylsilane -have been investigated in a fast flow reactor. Under our experimental conditions hydrogen abstraction from the Si-H bond is followed by combination of hydrogen atoms with the corresponding silyl radicals. The molecules formed in this wa...

The kinetics and mechanism of the mercury‐photosensitized decomposition of hexamethyldisilane have been studied. It has been confirmed that the initially‐formed radical, Me 3 SiSi(Me 2 )CH 2 , undergoes a unimolecular rearrangement; Arrhenius parameters have been measured for this rearrangement and for subsequent reactions of the rearranged radical...

CH 3 ) 3 SiCH 2 radicals, formed in the primary process (1) magnified image decompose according to (4) magnified image in the temperature range 650 K ‐ 800 K. The activation energy for process (4) has been measured to be 170 ± 8 kJ/mol. This value allows one to calculate an upper limit for the heat of formation of 2‐methyl‐2‐silapropene Δ H f ⁰ ≤ ‐...

The Arrhenius parameters of the reaction (3) equation image have been determined relative to the recombination of the trimethylsilyl radicals equation image yielding E A (3) — 1/2 E A (6) = 67 ± 6 kJ mol ⁻¹ and A (3)/ A (6) 1/2 = 10 −7±0.5 cm 3/2 s −1/2 . The rate constant for the back reaction (‐3) equation image has been determined to be equation...

An experimental study of the title reaction over the temperature range 250 to 459 K is described that uses the discharge‐flow technique, laser‐induced–fluorescence detection of OH and simultaneous monitoring of O and H atoms. In a teflon or halocarbon wax‐coated flow tube, the reaction is well behaved and free from surface effect interference, but...

The fluorescence depolarization of 1,6-diphenyl-hexatriene was used to study the dynamic properties of the hydrophobic regions of the lipid envelopes of ortho- and paramyxoviruses as well as of the Rous sarcoma virus and of the membrane lipids of susceptible and nonsusceptible cells. The systems investigated where active and inactive influenza viru...

A kinetic model was constructed and partly solved to describe the migration of the fluorescence label 1,6-diphenylhexatriene (DPH) in both directions when enveloped viruses, labelled with DPH in their envelopes are in contact with unlabelled cells or cell labelled in their membranes are in contact with unlabelled enveloped viruses. The central assu...

The fluorescence depolarization of 1,6-diphenyl-hexatriene was used to study the dynamic properties of the hydrophobic regions of the lipid envelopes of ortho- and paramyxoviruses as well as of the Rous sarcoma virus and of the membrane lipids of susceptible and nonsusceptible cells. The systems investigated where active and inactive influenza viru...

A kinetic model was constructed and partly solved to describe the migration of the fluorescence label 1,6-diphenylhexatriene (DPH) in both directions when enveloped viruses, labelled with DPH in their envelopes are in contact with unlabelled cells or cell labelled in their membranes are in contact with unlabelled enveloped viruses. The central assu...

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Durch Reaktion von photolytisch erhaltenen Wasserstoffatomen mit SiI-I4 erzeugte Silylradikale reagieren nach 2 Reaktionswegen A und B, die durch Isotopenmarkie- rung unterschieden werden können.

Silylradikale reagieren nach zwei Reaktionswegen ab: Rekombination zu einem hoch schwingungsangeregten Disilan Disproportionierung zu Silylen und Silan. Das Silylen verschwindet in einer sehr schnellen Einschubreaktion, ebenfalls unter Disilanbildung. ‐ Die beiden Reaktionswege (1) und (2) können durch Isotopenmarkierung unterschieden werden. Das...

Chemical-ionization mass spectra for chlorosilane, trichlorosilane and tetrachlorosilane have been obtained using methane as the reactant gas.Three types of ionic-transfer reactions were detected. Proton transfer to sample molecules was found for all three chlorinated silicon compounds and was the dominant chemical-ionization reaction at higher ion...

Heiße H-Atome, die durch Photolyse von HJ mit einer Zink-Resonanzlampe gebildet werden, reagieren mit SiD4 überwiegend unter Abstraktion.

Heiße Wasserstoffatome, die durch Photolyse von HJ mit einer Zink-Resonanzlampe gebildet werden, reagieren mit SiD4 überwiegend unter Abstraktion. Daneben finden auch eine atomare und eine molekulare Substitutionsreaktion statt, wobei die substituierten D-Atome ebenfalls heiß entstehen. Für die integrale Reaktionswahrscheinlichkeit der heißen Wasse...

The Reaction of Hydrogen Atoms with Silane; Arrhenius Parameters and Kinetic Isotope Effect Relative rate constants were measured for the systems H + C 2 H 4 /SiD 4 and D + C 2 D 4 /SiH 4 over a wide temperature range. From the known arrheniusparameter for the reaction H + C 2 H 4 the activation energy E A and the preexponential factor A of the abs...