On the reactions of ortho-positronium with methylmaleic and methylfumaric acids

Abstract

The o-Ps quenching reactions promoted by methylmaleic (citraconic) and methylfumaric (mesaconic) acids were investigated in aqueous solutions in order to compare their rate constants with those of maleic and fumaric acids. As expected, it was found that the rate constants of citraconic and mesaconic acids are almost equal and are much less than that of maleic acid, which in turn is less than that of fumaric acid. Moreover, it was ascertained that while the o-Ps quenching reactions promoted by maleic and fumaric acids seem to be diffusion controlled, the quenching reactions promoted by citraconic acid are kinetically controlled, its activation energy being 0.45±0.03 eV, which is significantly greater than the activation energy of diffusion-controlled reactions occurring in water, 0.18±0.01 eV.