Chemical Aspects of the Generation, Trapping, and Decay of Atomic Hydrogen in AlF3 and CaF2

Hydrogen atoms were generated in the matrices AlF3 and CaF2 at room temperature by ionizing radiation (γ and UV) and were investigated by electron paramagnetic resonance spectroscopy. To gain information on the nature of the hydrogen precursors and hydrogen traps within the solid matrices, studies regarding defined thermal and chemical influence, as well as mechanical impact on the fluoridic matrices before and after irradiation were the focus of this work. Impurities such as HO– and hydrocarbons were identified as potential precursors. The hydrogen traps were characterized by means of their spatial distribution within the different samples and by their energetic states (“trap‐depth”). In this respect, the rate constants, which were determined for different temperatures, turned out to be a valuable tool. Similarities and differences regarding the generation and stabilization of atomic hydrogen in AlF3 and CaF2 were worked out. Also, the influence of the type of ionizing radiation was elucidated. Whereas the comparison of AlF3 and CaF2 was dominated by similarities, significant differences were found for rather molecular siloxane cages R8Si8O12, especially regarding their reaction upon UV excitation and the possibility to resolve super‐hyperfine splittings. It is well known that hydrogen atoms can be generated in the matrices AlF3 and CaF2 at room temperature by ionizing radiation. To learn more about the nature of the hydrogen precursors and hydrogen traps, electron paramagnetic resonance spectroscopy studies regarding defined thermal and chemical influence, as well as mechanical impact on the fluoridic matrices before and after irradiation are performed.