Positrons in resorcinol

The temperature dependence of parameters describing the positron lifetime spectrum in resorcinol has been investigated. It was found that the solid phase transition point is located near 353 K, but over several K the transition is very slow, its rate lies in the range of days. The dimensions of positronium traps (free volumes) were estimated from crystallographic data. In spite of the non-spherical shape of these free volumes the o-Ps lifetime and its temperature dependence calculated from the popular Tao-Eldrup formula are relatively consistent with the experimental values. The main features of the temperature dependence of the positronium formation probability can be explained in the framework of the spur model. The increase in probability in the region below the transition point may be the result of ion-molecule reactions in the spur, or of the dependence of the Ps trapping probability on the trap size.