Positron irradiation effects in simple organic solids

Selection of the results of long-term studies on irradiation effects observed in solid long-chain alkanes and alkenes is presented in this work. Increase of ortho-positronium intensity with time at low temperature observed in alkanes is similar to the intensity changes occurring in polymers. Temperature changes of ortho-positronium intensity at its saturation value are explained by increase of positron mobility at the lowest temperature and thermal detrapping of electrons at higher temperature. Estimated activation enthalpy for odd numbered alkanes is about 0.6 eV, while for even numbered ones the enthalpy is 1 eV. Main fraction of electron traps is connected with interlamellar voids in the crystal structure of alkanes. Long-term measurements allow to observe an intensity decrease due to recombination of electrons involved in positronium formation with other irradiation products. Particularly glassy form of unsaturated hydrocarbon n-tridecene is characterized by distinct radical and ion related effects.