Positron annihilation study of the free volume changes in bifocal contact lenses
Chem. Met. Alloys 4 (2011) 13-17
Jacek FILIPECKI, Piotr KORZEKWA, Katarzyna FILIPECKA, Małgorzata HYLA, Dominika KORZEKWA, Edmund GOLIS, Witold KORZEKWA
Positron lifetime spectroscopy has been applied to study free volume related properties of bifocal contact lenses. The measurements were made on new lenses and then after one, two, and three weeks wearing. The longest lifetime, obtained via three-component analyses of the spectra, was associated with the pick-off annihilation of ortho-positronium trapped in the free volume. After wearing of the lenses, changes in the ortho-positronium lifetimes and the relative intensity of the longest component were observed. The results are discussed on the basis of a free volume model.
Typical curve of spectrum lifetime for the measured samples of bifocal lenses.
Positron annihilation / Contact lenses / Positronium / Free volumes