New organic compound based on ionic liquids for nuclear detection and radiation discrimination

The purpose of this study was to analyze new scintillating ionic liquids to be used in detection and neutron gamma discrimination. These molecules were exposed to different kinds of radiation to measure the emitted fluorescence with nanosecond scale. From a fundamental point of view, we studied the interaction between our molecules and nuclear radiation that finally led to the emission of light. Phenomena that cause light emission were divided in two groups. First, fast events, corresponding to molecular excitation phenomena, are visible through the prompt fluorescence. The second group is the one formed by direct or indirect ionizations responsible of charge pairs creation and giving rise to delayed fluorescence. Comparing these two fluorescence components, we could determine the yield among the various processes taking place in the matter and hence, we were able to characterize the medium's response to excitation. Then, using a model that describes dense matter, we found that pair recombination obeys to an inverse time power law, which corresponds to the transport processes leading to charge pair extinction. From an experimental point of view, a systematic study was performed on how the cation, anion and alkyl chain length influenced the discrimination capabilities of scintillating ionic liquids. We were able to create a simple model on charge recombination in these media. We concluded that recombination is localized or due to intermolecular phenomena among anion, cation and the oxazole group. A direct relation was found between discrimination and the chosen cation. Observations led us to deduce that the best cation for discrimination was the imidazolium. (author)