Near-diffusion-controlled reactions of muonium in sub- and supercritical water

article

2002

Physical Chemistry Chemical Physics

4

4

586

595

Rate constants are reported for near-diffusion-controlled reactions of muonium in sub- and supercritical water. Specifically, the spin-exchange interaction of muonium with Ni2 + and the addition of muonium to hydroquinone were studied as a function of temperature and pressure over a wide range of conditions, from standard to over 400 °C and 400 bar (the critical point of water is at 374 °C, 220 bar). At elevated temperatures the rate constants were found to have values far below those predicted by Stokes–Einstein–Smoluchowski theory. Furthermore, the temperature variation of the isobaric rate constants has a maximum in the subcritical region. The pressure dependence of the rate constants increases with temperature, consistent with the increase in compressibility of the solvent; the effective activation volumes are negative. Various models are explored to interpret the temperature and density dependence of the kinetic data. It is concluded that a key factor in the drop of rate constants at high temperature is the cage effect, in particular the number of collisions between a pair of reactants over the duration of their encounter.

https://doi.org/10.1039/B108656A

10.1039/b108656a

1463-9076

English

Royal Society of Chemistry

Peer reviewed

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© 2002. Royal Society of Chemistry.