Pick-off models in the studies of mesoporous silica MCM-41. Comparison of various methods of the PAL spectra analysis

The results of models, extending the Tao–Eldrup model to free volume radii R>1nm, are discussed. The influence of free volume size and geometry on ortho-positronium lifetime was examined. Theoretical curves were compared to available experimental data. Then the models were used to obtain information about free volume sizes in MCM-41 porous silica. Numerical analysis of MCM-41 lifetime spectra is difficult due to their considerable complexity. In order to verify the results, various methods of PAL spectra analysis, e.g., deconvolution, fitting, etc., were involved.