Positron Annihilation in Aqueous Solutions

Interactions of positronium with cobalt(2+) in water: mechanisms and temperature effects

“…Although the existence of spin conversion has been demonstrated unambiguously in some instances, particularly using AC in the case of paramagnetic gases1 2345678 or in the presence of a magnetic field,9 the results obtained from LS for paramagnetic ions in solution have not always been convincing and have sometimes been conflicting with those from AC measurements. 10 Recently, results have been reported on the reactions of Mu with a variety of dia-and paramagnetic ions in water.11 12*Although only the disappearance of the Mu triplet-state component can be followed with the muonium spin rotation technique used, and not its increase from the singlet state upon conversion, the authors' conclusion pointed to the existence of spin conversion in the presence of the paramagnetic ions.…”

Temperature and (polar) solvent effects on positronium reactions with nitroxyl free radicals

“…7"11 The PAC results were presented in terms of / , representative of the changes with solute concentration of the narrow-component intensity in the PAC curves, ascribed to p-Ps. However, 7 was derived on a somewhat arbitrary basis, 6,11,12 usually involving the definition of a central area in the PAC momentum distribution curves, which may lead to rather discordant values according to the definition chosen. Owing to the great importance of the precise determination of / to support the hypothesized reactions, some doubt persists on the proposed interpretations.7"11 Furthermore, the influence of temperature for a better understanding of the spin interactions has been studied very little.…”

Positronium interactions with Cu(II) Ions in water

“…A few years after, Trumpy [5] presented ACAR measurements in disagreement with the above explanation. The point of discrepancy is that the ACAR curve for Cu~q + (2 M solution) is broader than the pure-water curve; this is in contrast with the enhancement of the narrow p-Ps component expected for pure SE reactions.…”