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Monte-Carlo simulation of photodissociation spectra from molecular beam experiment
Košťál, Pavel ; Fárník, Michal (advisor) ; Havlíček, Josef (referee)
Within the framework of my BSc Thesis I became familiar with a unique molecular beam apparatus for cluster studies. I have learned about clusters and molecular beams, mass spectrometry, photodissociation and molecular dynamics. My specific task was to generace several computer programs for data acquisition and evaluation of~the~present experiments: (1) A program for TOF to mass spectra conversion. This program facilitated immediate evaluation of~the~measured mass spectra. (2) A program for TOF spectra conversion into the kinetic energy distribution KED of the fragments, which provides immediate information about the studied photochemical processes. The immediate information provided by both these programs enable a more effective control of the experiment. (3) Finally, I have modified Monte-Carlo simulation program. This program serves the ultimate TOF→ KED conversion of the experimental data. All the programs were tested with photodissociation of a well studied system of HBr cluster, and they have shown a good performance.
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Investigation of photodissociation dynamics implementing the velocity map imaging technique
Moriová, Kamila ; Fárník, Michal (advisor) ; Profant, Václav (referee)
The aim of this thesis is to investigate the effects of change in the chain length and chlorine group position on C-Cl bond photodissociation dynamics of chloroalkanes using the velocity map imaging (VMI) method. Three different chloroalkanes are studied (1-chloropropane, 2-chloropropane, 1-chloropentane) and compared with previously investigated chloromethane. Regardless of the parent chloroalkane, measured kinetic energy distributions (KEDs) of chlorine photofragments exhibit a single peak at energy around 0.8 eV. Photodissociation of higher chloroalkanes involves a recoil of a semi-rigid alkyl fragment, whose internal energy absorbs 40-60% of the total available energy. For chloromethane, however, only less than 10% of the available energy goes into the alkyl fragment excitation. Measured results of the energy partitioning are compared with cal- culations based on classical impulsive models. VMI experiment in combination with theory also yields information about the nature of electronic transition and probability of the intersystem crossing. Analysis indicates that the direct absorp- tion into the triplet state is more probable for the chloroalkanes with longer chain length, especially for the branched one. 1
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Photodissociation studies of xanthene dyes, iron(III) azido complexes and hemithioindigo molecular switches in the gas phase
Navrátil, Rafael ; Roithová, Jana (advisor) ; Žabka, Ján (referee) ; Volný, Michael (referee)
Electronic excitation triggered by the absorption of light enables numerous chemical, physical and biological processes and transformations. Accordingly, full control over the processes involving excited molecules requires an in-depth knowledge of electronic UV/vis spectra and potential energy surfaces. Unsurprisingly, most electronic spectra are acquired in the condensed phase in which molecules are dissolved and most transformations occur. However, our knowledge of excitation, transformations and processes at the level of isolated molecules is still limited, partly because such studies require unconventional experimental approaches and equipment. This Thesis describes experimental methods for recording electronic spectra of isolated molecules in the gas phase by ion spectroscopy, which combines mass spectrometry with optical spectroscopy. Using these methods, experimental factors which affect the electronic excitation and therefore the electronic spectra of ions were determined and evaluated for various fluorescent xanthene dyes, iron-containing complexes and molecular pho- toswitches. Furthermore, factors which govern photochemical processes, such as photo- oxidation, photoreduction and photoisomerization, were also analyzed in detail, with surprisingly different outcomes from previous studies...
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Monte-Carlo simulation of photodissociation spectra from molecular beam experiment
Košťál, Pavel ; Fárník, Michal (advisor) ; Havlíček, Josef (referee)
Within the framework of my BSc Thesis I became familiar with a unique molecular beam apparatus for cluster studies. I have learned about clusters and molecular beams, mass spectrometry, photodissociation and molecular dynamics. My specific task was to generace several computer programs for data acquisition and evaluation of~the~present experiments: (1) A program for TOF to mass spectra conversion. This program facilitated immediate evaluation of~the~measured mass spectra. (2) A program for TOF spectra conversion into the kinetic energy distribution KED of the fragments, which provides immediate information about the studied photochemical processes. The immediate information provided by both these programs enable a more effective control of the experiment. (3) Finally, I have modified Monte-Carlo simulation program. This program serves the ultimate TOF→ KED conversion of the experimental data. All the programs were tested with photodissociation of a well studied system of HBr cluster, and they have shown a good performance.
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Ion imaging method in molecular beam photodissociation experiments
Košťál, Pavel ; Fárník, Michal (advisor) ; Roučka, Štěpán (referee)
During my master thesis I became familiar with ion imaging and velocity map imaging (VMI) techniques in experiments with molecular beam. My major contribution was writing a computer program for data acquisition and pre-analysis. The program features initial filtering of the data, improving significantly signal to noise ratio. Non-trivial effort was required to make the program compatible with three different CCD cameras implemented on different experiments in the laboratory. I have also simulated ion trajectories in VMI and wrote a program code to imulate VMI image distortions due to imperfections in apparatus geometry. These programs will be useful in aligning and tuning the apparatus. Finally, I wrote a program for data manipulation and conversion to formats compatible with various data analysis programs available in the laboratory. All the above programs I have tested by measurements of 243 nm photodissociation of HBr molecules.
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