Effects of local heating and premelting in the terminal part of the e+ track

The terminal part of the e(+) track (the positron blob) is formed during ionization slowing down and subsequent ion-electron recombinations produced by a positron. It releases up to 1 keV of energy, which is converted into heat within few picoseconds. If a bulk temperature of a medium is below, but close enough to its melting point, some region of a substance may melt, yielding a peculiar temperature dependence of the lifetime (LT) spectra. We have estimated properties of the molten region with a help of macroscopic heat conduction equation and suggested a model describing temperature dependence of the ortho-positronium lifetime in frozen methanol, ethanol, butanol and water close to their melting points.