Reactions of Hydroxyl Radicals with Oxygenated Hydrocarbons in the Gas Phase: A Laser Photolysis/Laser-Induced Fluorescence Study

Author: Cornelie Bänsch

Publisher: Logos Verlag Berlin GmbH


Category: Science

Page: 173

View: 895

Hydroxyl radicals (OH) play a key role in ignition processes and in the atmosphere. Thus, the detailed knowledge of the kinetics of OH reactions is crucial in combustion and atmospheric research. In this work, an experimental approach for time-resolved studies of OH radical reactions at high pressures with pulsed laser photolysis/laser-induced fluorescence was revised and the reactions of dimethyl ether, diethyl ether, and dimethoxymethane with OH radicals were investigated in detail. The results reveal a deeper insight into the reaction processes of ether compounds with OH in general, contributing to a better understanding of the combustion of different biofuels and fuel additives.

Die Fakultät für Technische Chemie/The Faculty of Technical Chemistry

Author: Herbert Danninger

Publisher: Böhlau Verlag Wien


Category: History

Page: 156

View: 537

The Faculty of Technical Chemistry introduces itself! The historical development of Chemistry and Chemical Engineering at the TU is presented in the five chapters of this volume, starting with the foundation of the Imperial Royal Polytechnic Institute in 1815 and reaching all the way to the TU Wien in 2015, including current research highlights of the Faculty of Technical Chemistry and an overview of its modern equipment and building infrastructure, curricula, and excellent contact with the alumni. A lively picture of the teaching and research of this successful faculty and fully renovated Getreidemarkt Campus is painted, making, however, no claims to completeness.

Progress in Physical Chemistry - Volume 1

Different Aspects of Intermolecular Interaction - Reviews from Zeitschrift für Physikalische Chemie

Author: Helmut Baumgärtel

Publisher: Walter de Gruyter GmbH & Co KG


Category: Science

Page: 290

View: 957

"Progress in Physical Chemistry" is a collection of recent "Review Articles" published in the "Zeitschrift fur Physikalische Chemie." The aim of a "Review Article" is to give a profound survey on a special topic outlining the history, development, state of the art and future research. Collecting these Reviews the Editor(s) of "Zeitschrift fur Physikalische Chemie" intend to counteract the expanding flood of papers and thereby to give students and researchers a means to obtain fundamental knowledge on their special interests. The first volume of "Progress in Physical Chemistry" is mainly focussed on intermolecular interaction, also glancing at topics that are marginally touched. Contents: M. Havenith*, G. W. Schwaab, Attacking a Small Beast: Ar-Co, a Proto-type for Intermolecular Forces; O. Dopfer, IR Spectroscopy of Microsolvated Aromatic Cluster Ions: Ionization-Induced Switch in Aromatic Molecule-Solvent Recognition; C. F. Kaminski, Fluorescence Imaging of Reactive Processes; T. Stangler, R. Hartmann, D. Willbold, B. W. Konig*, Modern High Resolution NMR for the Study of Structure, Dynamics and Interactions of Biological Macromolecules; M. Drescher, Time-Resolved ESCA: a Novel Probe for Chemical Dynamics; C. Donner: Kinetics of Electrochemical Phase Formation in Two-Dimensional Systems; C. Czeslik, Factors Ruling Protein Adsorption; T. Kopp, Homogeneous Ice Nucleation in Water and Aqueous Solutions"

New Enhanced Sensitivity Infrared Laser Spectroscopy Techniques Applied to Reactive Plasmas and Trace Gas Detection

Author: Stefan Welzel

Publisher: Logos Verlag Berlin GmbH


Category: Science

Page: 197

View: 954

Infrared laser absorption spectroscopy (IRLAS) employing both tuneable diode and quantum cascade lasers (TDLs, QCLs) has been applied with both high sensitivity and high time resolution to plasma diagnostics and trace gas measurements. TDLAS combined with a conventional White type multiple pass cell was used to detect up to 13 constituent molecular species in low pressure Ar/H2/N2/O2 and Ar/CH4/N2/O2 microwave discharges, among them the main products such as H2O, NH3, NO and CO, HCN respectively. The hydroxyl radical has been measured in the mid infrared (MIR) spectral range in-situ in both plasmas yielding number densities of between 1011 ... 1012 cm-3. Strong indications of surface dominated formation of either NH3 or N2O and NO were found in the H2-N2-O2 system. In methane containing plasmas a transition between deposition and etching conditions and generally an incomplete oxidation of the precursor were observed. The application of QCLs for IRLAS under low pressure conditions employing the most common tuning approaches has been investigated in detail. A new method of analysing absorption features quantitatively when the rapid passage effect is present is proposed. If power saturation is negligible, integrating the undisturbed half of the line profile yields accurate number densities without calibrating the system. By means of a time resolved analysis of individual chirped QCL pulses the main reasons for increased effective laser line widths could be identified. Apart from the well-known frequency down chirp non-linear absorption phenomena and bandwidth limitations of the detection system may significantly degrade the performance and accuracy of inter pulse spectrometers. The minimum analogue bandwidth of the entire system should normally not fall below 250 MHz. QCLAS using pulsed lasers has been used for highly time resolved measurements in reactive plasmas for the first time enabling a time resolution down to about 100 ns to be achieved. A temperature increase of typically less than 50 K has been established for pulsed DC discharges containing Ar/N2 and traces of NO. The main NO production and depletion reactions have been identified from a comparison of model calculations and time resolved measurements in plasma pulses of up to 100 ms. Considerable NO struction is observed after 5 ... 10 ms due to the impact of N atoms. Finally, thermoelectrically cooled pulsed and continuous wave (cw) QCLs have been employed for high finesse cavity absorption spectroscopy in the MIR. Cavity ring down spectroscopy (CRDS) has been performed with pulsed QCLs and was found to be limited by the intrinsic frequency chirp of the laser suppressing an efficient intensity build-up inside the cavity. Consequently the accuracy and advantage of an absolute internal absorption calibration is not achievable. A room temperature cw QCL was used in a complementary cavity enhanced absorption spectroscopy (CEAS) configuration which was equipped with different cavities of up to 1.3 m length. This spectrometer yielded path lengths of up to 4 km and a noise equivalent absorption down to 4 x 10-8 cm-1Hz-1/2. The corresponding molecular concentration detection limit (e.g. for CH4, N2O and C2H2 at 1303 cm-1/7.66 Aem) was generally below 1 x 1010 cm-3 for 1 s integration times and one order of magnitude less for 30 s integration times. The main limiting factor for achieving even higher sensitivity is the residual mode noise of the cavity. Employing a 0.5 m long cavity the achieved sensitivity was good enough for the selective measurement of trace atmospheric constituents at 2.2 mbar.

Laser Spectroscopy 1

Basic Principles

Author: Wolfgang Demtröder

Publisher: Springer


Category: Science

Page: 496

View: 533

Keeping abreast of the latest techniques and applications, this new edition of the standard reference and graduate text on laser spectroscopy has been completely revised and expanded. While the general concept is unchanged, the new edition features a broad array of new material, e.g., ultrafast lasers (atto- and femtosecond lasers) and parametric oscillators, coherent matter waves, Doppler-free Fourier spectroscopy with optical frequency combs, interference spectroscopy, quantum optics, the interferometric detection of gravitational waves and still more applications in chemical analysis, medical diagnostics, and engineering.

Air toxics and water monitoring

21 June, 1995, Munich, FRG

Author: George M. Russwurm

Publisher: Society of Photo Optical


Category: Computers

Page: 178

View: 927