Sujet de stage / Master 2 Internship

The internship will make it possible to adapt the process of flash photolysis of H2O2 to its measurement in operando under ionizing radiation. For the proof of concept, it will be necessary to determine the best chemical system and the protocol to analyze the concentration of H2O2 formed during the radiolysis of water with heavy ions.

In radiation chemistry, the formation of H2O2 during the radiolysis of water with ion beams (protons, alpha, etc.) is poorly understood. Indeed, the analysis of H2O2 is only done by post-mortem analysis; meaning, when the irradiated sample is analyzed in the laboratory, a few minutes later. H2O2 is relatively stable, but 1/it disappears by reaction during radiolysis if it is not protected from attacks by the hydroxyl radical or the hydrated electron; 2/it disappears on contact with metallic particles/surface, even those present as impurities. Measurements of H2O2 formation under an ionizing particle beam are therefore very complex and often subject to controversy.
As H2O2 has the property of being easily photolyzed with laser excitation in UVA-B giving 2 hydroxyl radicals, we can use the nanosecond flash photolysis technique and the reactivity of species like Br-, Cl- or even O2 to measure the concentration of H2O2 over time, while the sample is being irradiated (in operando): this constitutes a 3-beam experiment.
The internship will therefore consist of using the LIDYL/DICO laser installation dedicated to nanosecond flash photolysis and testing/comparing different chemical systems to best configure an experiment which will ultimately be carried out under a pulsed ion beam. Before that, the experiment will be simulated with a deterministic code in order to take into account the complex process of water radiolysis.