POSITRONIUM FORMATION AND QUENCHING IN FROZEN AND LIQUID SOLUTIONS INOCTANOL

Pure octanol is examined in the liquid and solid state, together with solutions of two solutes promoting both inhibition and quenching of po sitronium (Ps): quinone, a Ps oxidizer, and free radical TMOPO, promot ing Ps spin conversion reactions. In all cases, the changes of both th e Ps lifetime and, to a lesser extent, intensity denote the five phase transitions expected between 123 and 294K. In contrast to a previous claim, no Pa quenching reactions are observed in the frozen solutions while Ps inhibition through electron capture by the solutes in the pos itron spur appears to be sensitive to the phase. In the liquid phase, the quenching reaction rate constants of either solute are higher by a factor of similar to 4 than what is expected on the basis of conventi onal expressions for diffusion-controlled reactions. (C) 1998 Elsevier Science B.V. All rights reserved.