Specifics of Interaction of Acetone Molecules with Quasi-free Electrons: Analysis of Positron Annihilation Characteristics in Aqueous and Alcoholic Acetone Solutions

Abstract

The yields of formation of radiolytic hydrogen (H2) and orthopositronium (o-Ps) in aqueous and alcoholic acetone solutions were experimentally determined. A decrease in the o-Ps yield with an increase in the acetone concentration is much weaker than the decline in the yield of solvated electrons (e–s) under picosecond pulse radiolysis conditions. In contrast, the decrease in the o-Ps yield is minimal in higher alcohols where the inhibiting action of acetone e–s is most pronounced. These findings seem to contradict the conventional concepts of Ps formation via the intratrack reaction of positron recombination with a track electron (e–), which competes with the reaction of e– scavenging by dissolved acetone molecules. This contradiction can be eliminated, assuming that the scavenging of e– by acetone begins from the formation of the weakly bound transient state (CH3)2CO···e– capable of donating e– to a positron. This opens up an additional pathway for the formation of the Ps atom.