|
|
Characterization of diode lasers and their application in monitoring of atmospheric pollution with photoacoustic detection
Cihelka, Jaroslav ; Civiš, Svatopluk (advisor) ; Strauch, Bohuslav (referee) ; Wild, Jan (referee) ; Zelinger, Zdeněk (referee)
4 Summary This thesis work was concemed with the spectroscopic characterization of a set of newly developed GalnAsSb/AlGaSb lasers. The spectral range of their laser emission was studied in dependence on temperature and drive current. The relation of threshold current versus temperature was also studied. These basic characteristics were obtained using the methods of FT spectroscopy, classic absorption technique, and photoacoustic detection of gaseous phase molecules. On the basis of the described measurements, the composition of the semiconductor material was optimized in order to reach the maximum overlap of the laser emission over the methane absorption lines. The possibilities of combining the GaInAsSb/AlGaAsSb and InAsSb/lnAsSbP-based lasers with the FT spectroscopy were also studied and the modulated beam was used as the source of drive emission for the spectrometer. The diode lasers were used for the detection of a highly-resolved spectra of gases, and in connection with the photocoustic detection, low concentrations oť gaseous polltrtants could be determined, mainly with formaldehyde, ammonia and methane. Co-operation with the Department of Electrochemistry (the J. Heyrovsky lnstitute of Physical Chemistry) allowed us to use photoacoustic detection for a quantitative assessment of the ammonia...
|
|
|
High resolution infrared spectroscopy as diagnostic tool for combustion and plasma chemistry
Zelinger, Zdeněk ; Nevrlý, Václav ; Grigorová, Eva ; Bitala, P. ; Dostál, Michal ; Suchánek, Jan ; Kubát, Pavel ; Engst, Pavel ; Ferus, Martin ; Kubelík, Petr ; Civiš, Svatopluk
Monitoring of transient species within combustion experiments (laminar flames, shock-tubes, flow reactors, etc.) is still relatively challenging task especially if application of non-invasive, i.e. optical detection methods is required. High resolution infrared spectroscopy is based on observation of the fine rotation structure that accompanies vibration transitions and thus provides direct information essential to characterization of both molecular structure and reaction dynamics. Thanks to its outstanding advantage enabling unambiguous assignment of specific molecular system according to its spectral feature, it can serve as a helpful tool for exploring complex reaction mechanisms as well as chemical reactivity of individual species present in laboratory flames or plasmas.\nPrevious studies gaining new insights into combustion and plasma chemistry as well as our recent advances targeted towards application of high resolution infrared spectroscopy for species concentration measurement in laminar flames are summarized here below.
|
|
|
Wavelength modulation spectroscopy for multicomponent ana-lytics of biomass burning tracers
Dostál, Michal ; Válek, V. ; Suchánek, Jan ; Kristlová, E. ; Roupcová, P. ; Zelinger, Zdeněk ; Nevrlý, Václav ; Bitala, P. ; Vašinek, M. ; Kubát, Pavel ; Ferus, Martin ; Civiš, Svatopluk
The potential of Tunable Diode Laser Absorption Spectroscopy (TDLAS) for monitoring of several species produced by biomass burning is in focus of this work. The infrared spectra of selected molecules (HCOOH, C2H2, CH3CN, N2O, CH3OH, CH3COCH3) are measured in laboratory conditions and the selectivity and of this method is demonstrated.
|
|
| |
|
| |
|
| |
|
|
Fourier transform infrared spectroscopy: application in a study of transient species in discharge and ablation plasma
Kubelík, Petr ; Civiš, Svatopluk (advisor) ; Wild, Jan (referee) ; Rohlena, Karel (referee)
The present dissertation consists of two thematically related parts. The first one (includes two publications) deals with the study of chemical pro- cesses and spectroscopy of highly reactive particles produced in the discharge plasma. This part includes the analysis of ro-vibronic CN radical transitions in the infrared region and the study of chemical reactions in pulsed dischar- ges. The discharge was used as a tool for research of decomposition of simple precursors (acetonitrile, formamide and BrCN) and the subsequent formation of intermediates and reaction products in plasma. The obtained experimental results were interpreted using a numerical model developed in context of this work and used to simulate the kinetics of the studied systems. The second part (includes seven works) is aimed at high-resolved spectro- scopy of metals in the ablation plasma. A total of six different metals were studied: Au, Ag, Cu, Cs, K and Na. The main motivation for spectroscopic research on metals in the infrared region is to obtain information on atomic metals transitions, which are particularly important for astronomical identi- fication of lines in the spectra of stars and their spectroscopic assignments. Each publication contains a summary of the analyzed atomic transitions of which a considerable portion had not...
|
|
|
The Study of Transient Species and Precursors of Biomolecules using Spectroscopic Techniques
Ferus, Martin ; Civiš, Svatopluk (advisor) ; Šponerová, Judit E. (referee) ; Wild, Jan (referee)
The presented thesis is focused on a spectroscopic study of unstable radicals, ions and molecules in a positive column glow discharge and laser plasma. The research of these fragments is supplemented by a study of biomolecules formation from these species and influence of catalysts. Molecular dynamics of radicals, ions and unstable molecules has been studied using a time resolved Fourier transform infrared spectroscopy. Time resolved spectra of CH4, HCONH2, BrCN, CH3CN, CF3Br, (CF3)2CHBr positive column glow discharges have been measured and simulated using a kinetic model including molecular dynamics, collisions and chemical and radiation transfer processes. The model has been compared with our experimental results and time resolved spectra were described in details. Fit to a complex reaction mechanism has been used to estimate a rate constant of a HCN conversion to HNC by a collision with H radical. The study of precursors of biomolecules was focused on chemical consequences of a laser induced dielectric breakdown in formamide vapor and gaseous carbon monooxide with 18 O labeled water. Dissociation products have been detected using the Fourier transform absorption spectroscopy. The experimental results have been explained by a help of a chemical laser spark dynamics model. Additionally, our the...
|
|
|
Formation of nucleobases from formamide initiated by high-power density energy events
Michalčíková, Regina ; Civiš, Svatopluk (advisor) ; Šponerová, Judit E. (referee)
This Master's thesis deals with determination of nucleobases in formamide samples (pure or catalyzed form) after their initiation by high-power density energy events. The theoretical part states the reader to the problems of prebiotic chemistry and acquaints him with the various theories of the origin of the nucleobases. The experimental part deals with the analysis of the samples initiated by Laser System PALS, which was used for the simulation high-power density energy events. For the identification and determination of the final products of laser plasma initiated chemical reactions in the gaseous phase of the samples was used the Fourier Transform Infrared Spectroscopy. The liquid part of the samples and the nucleobases in this part were analyzed by the gas chromatography with the mass detection.
|
|
|
Formation of organics molecules initiated by high-power density energy events in planetary atmospheres
Kamas, Michal ; Civiš, Svatopluk (advisor) ; Zelinger, Zdeněk (referee)
The focused laser beam delivered by the high-power laser system PALS was used for laboratory simulation of high-energy-density events in a planetary atmosphere. Several model gas mixtures were prepared to mimic the mildly reducing early Earth's atmosphere (CO-N2-H2O) as well as the atmosphere of Saturn's moon Titan and the strongly reducing early Earth's atmosphere (CH4-N2-H2O). In situ investigation of transient species generated by the laser-induced dielectric breakdown in the gaseous mixtures was performed by optical emission spectroscopy (OES). Final products of laser-plasma initiated chemical reactions were identified and determined by advanced mass-spectrometry (SIFT-MS) and absorption FT-IR spectroscopy. High-power laser system SOFIA was utilized to simulate in our laboratory a high-velocity impact into the icy satellites of the outer planets of the Solar system. OES was engaged in probing the plasmas produced by the SOFIA beam focused on ice surfaces (water, methanol, formamide), while final products were analyzed by means of gas chromatography (GC/MS) and mass-spectrometry (SIFT-MS).
|
guest ::
