Positronium Annihilation in Freshly Defrosted Thawed Water

Variation in the parameters of the positron annihilation lifetime spectra in pure water presubjected to freeze–thaw processes is studied. It is shown that in freshly defrosted water (at 1–2°С), the ortho-positronium lifetime and formation probability tend to the corresponding values in ice (near its melting point), and after about 10 h they reach the values corresponding to ordinary water at the same temperature. It indicates that no complete (at molecular level) defragmentation of the ice lattice occurs immediately after ice melting, and rigid ice-like clusters, in which positronium formation is also possible remain in the liquid phase for several hours.