Spektroskopické metody pro koncentrační měření a kalibraci reaktivních prvků

Import 07/02/2011The topic of my dissertation is focused on utilization of spectroscopic methods for detection and measurement of various molecular systems that are interesting from the point of view of their reactivity and role that they play in atmospheric chemistry, astrochemistry, human body, or in simulated plasma processes. Description of the work is divided into four thematic parts describing four independently performed experiments. The very first analyses of the asymmetrical vibration ν4 band and the symmetrical ν2 band of the FCO2· radical, that belong among significant intermediate products of degradation processes of halogen hydrocarbons, were performed within this work. The detailed analysis led to determination of rotational constants, centrifugal distortion constants, and fine splitting constants of both bands. For the first time in history we performed the spectroscopically unambiguous identification of the molecular radical ion CS+ using the microwave spectroscopy with high spectral resolution in the frequency range of 414 to 622 GHz. The complex analysis allowed us to exactly determine the values of the rotational constant, fine splitting constant, and hyperfine splitting constant. It was also designed and performed experiments including measurements of spectra of cyan BrCN and CH3CN substances using the time resolved Fourier transform infrared spectroscopy. It was studied behavior of these molecules and their disintegration products in the low temperature plasma environment. Finally, I have studied the ecological impact of ammonia on the environment and influence of trees on the amount of ammonia in the air, and designed and assembled the optoacoustic cell for the experimental arrangement of the laser optoacoustic detection method for measuring trace amounts of ammonia and other gaseous substances.Prezenční040 - Katedra bezpečnostního managementuvyhově

Méthodes spectroscopiques pour les mesures de concentration et la calibrage de gaz réacttifs

Le sujet de ma thèse concerne l´application des méthodes spectroscopiques utilisées pour la détection et la mesure de concentration de différentes espèces intéressantes du point de vue de leur réactivité et pour leur rôle dans des domaines très variés comme en chimie atmosphérique, en astrochimie ou encore dans le corps humain. Pour la première fois l´analyse de la bande de vibration asymétrique v4 du radical FCO2 a été effectuée ainsi que celle de la bande v2 . FCO2 est un des produits intermédiaires importants dans les processus de dégradation des carbures d´halogène. Ce travail à conduit à la détermination précise des constantes moléculaires (y compris celles de structure fine) des deux bandes de vibration.Nous avons également effectué l´identification de l´ion radicalaire CS+ par spectroscopie millimétrique, dans la gamme de fréquence 414 - 622 GHz. L´analyse globale avec les données infrarouges disponibles a permis de déterminer précisément les valeurs de la constante de rotation et de la constante de structure fine. J’ai ensuite effectué la mesure des spectres des cyanures BrCN et CH3CN par spectroscopie infrarouge à transformée de Fourier. J´ai aussi étudié la réactivité de ces molécules ainsi que leurs produits de décomposition dans un plasma à basse température. Finalement, j´ai étudié l´impact écologique de l´ammoniaque sur l´environnement ainsi que le rôle des arbres sur la concentration en ammoniaque atmosphérique. Une cuve opto-acoustique a ainsi été conçue pour mesurer les concentrations de l´ammoniaque et d´autres gaz présents en très faible quantité.Description of the work is divided into four thematic parts describing four independently performed experiments. The analyses of the asymmetrical vibration ν4 band and the symmetrical ν2 band of the FCO2 radical, that belong to significant intermediate products of degradation processes of halogen hydrocarbons, were performed for the first time within this work. The detailed analysis led to the determination of the rotational constants, centrifugal distortion constants and fine structure constants for both bands. For the first time we performed the unambiguous identification of the radical ion CS+ by high resolution millimetrewave spectroscopy in the frequency range 414 - 622 GHz. The complex analysis allowed us to accurately determine the values of the rotational constant as well as the fine structure constant. Experiments were also perform to measure spectra of cyan BrCN and CH3CN using time resolved Fourier transform infrared spectroscopy. These molecules as well as their disintegration products in the low temperature plasma environment were carefully studied. Finally, I have studied the ecological impact of ammonia (NH3) on the environment and the influence of trees on the amount of ammonia in the air. For this purpose, an optoacoustic cell was designed and assembled to measure trace amounts of ammonia and other gaseous substances

First analysis of the high resolution FTIR spectrum of the v(2) band of the FCO2 radical at 970.2 cm(-1)

International audienceThe infrared spectrum of the fluorocarboxyl radical, FCO2, was recorded at high resolution (0.0035 cm−1) in the 600−1400 cm−1 region on a Bruker IFS 120 HR Fourier transform spectrometer of the University of Wuppertal. The analysis of the A-type nu2 band of FCO2 (CF stretching mode) centred at 970.208 cm−1 was performed taking use of the ground state parameters achieved by Kolesnikova et al. [Kolesnikova L, Varga J, Beckers H, Simeckova M, Zelinger Z, Nova Striteska L, Kania P, Willner H, Urban S. J. Chem. Phys. 128, 2008, pp. 224302-1-8]. For the FCO2 radical, the nu2 transitions are, in principle, splitted into two spin - rotation subcomponents corresponding to J= N +/-1/2. However the spin- rotation parameters in the 21 vibrational state have values similar to those of the ground state, and spin-rotation doublings are observable only for the weaker transitions involving medium Ka or Kc values in the P and R branches. The nu2 fundamental band is weakly perturbed by the 2nu5 dark overtone band at 965.4 cm−1 and the 21 and 52 energy levels of FCO2 are coupled through Fermi type resonances. The final energy level calculation was performed accounting both for the spin -rotation interaction within the 21 and 52 vibrational states, and the 21 52 Fermi-type resonances

Allan variance for optimal signal averaging-monitoring by diode–laser and CO2 laser photo-acoustic spectroscopy

The concept of the Allan variance has been utilized to test the detection abilities of two powerful experimental methods for trace gas monitoring: IR diode–laser and CO2 laser photo-acoustic spectroscopy. The detection of stable molecules (OCS, allene, CH3OH), and unstable species (ozone, short-lived free radical CN and molecular ion ArD+) have been compared. An approach for studies of the influence of the reactivity on the optimal averaging time for the minimum detectable concentration is demonstrated

On the instability of a modified cup-burner flame in the infrared spectral region

This study describes the modification of a standardised cup-burner apparatus. The replacement of the original glass chimney is performed by shielding a nitrogen co-flow enabled measurement at a wavelength of 3.9 μm. This modification, together with a special arrangement of the measuring system (spectral filtering, data acquisition and post-processing), permitted the observation of various types of hydrodynamic instabilities, including transition states. The advantages of our arrangement are demonstrated with an ethylene non-premixed flame with high sooting tendency. Two known modes of hydrodynamic instability (varicose and sinuous) that occur in buoyant flames were studied and described quantitatively. Based on the intensity of the infrared emissions, we identified and qualitatively described the modes of periodic hydrodynamic instability that are accompanied by flame tip opening, which has not been observed for this type of flame

CFD modelling for atmospheric pollutants/aerosols studies within the complex terrains of urban areas and industrial sites

Computational fluid dynamic (CFD) modelling of pollution dispersion and chemical conversion to aerosol particles in the atmospheric boundary layer (ABL) has been studied. The investigation focused on the numerical modelling above complex orographic terrains of urban areas and industrial sites including the dispersion of toxic substances in the air as a result of accidents. A finite-rate model of chemical reactions, including the turbulence chemistry for modelling the reaction between nitric acid and ammonia, has been applied. As supporting experiments, online monitoring of the spatial distribution of pollutants and aerosols has been performed above real complex areas. Minimal detectable concentrations 8 µg m−3 (SO2), 20 µg m−3 (NO2), 2 µg m−3 (O3) and minimal detectable absorptivity 5 × 10−7 cm−1 (aerosols) have been reached.Web of Science541907

Time-resolved Fourier transform emission spectroscopy of CF3Br and CF3CFHCF3 in a pulsed electrical discharge

The environmentally important decomposition of halogenated species CF3Br and CF3CHFCF3 in helium discharge plasma was investigated by time-resolved high-resolution Fourier transform infrared emission spectroscopy. Contrary to classical pyrolysis, a deeper fragmentation of precursors up to atoms and lower molecular species was observed. Excited molecular products CF, CF2 and CF4 achieved the maximal concentration in the afterglow. The high concentration of all these species is in agreement with a kinetic model based on radical chemistry. The non-detectable concentration of CF3 can be connected to its high reactivity and the formation of more stable products, CF4 and CF2, by addition or release of a fluorine atom, respectively. Other products included HF, HBr, CO and cyano compounds that were produced by secondary reactions with traces of water vapor, atmospheric oxygen and nitrogen present in original industrial samples as impurities