Chemical constitution of 3d complexes and rate constants of ortho-para positronium conversion reactions

Lazzarini, A.L. Fantola; Lazzarini, E.

doi:10.1007/bf00672234

Cited by 9 publications

(6 citation statements)

References 16 publications

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“…for free e f + ; Ox = k Ox c for a redox reaction, c being the oxidant concentration; ␥ = k SE c for the conversion of o-Ps into p-Ps and therefore for o-Ps into p-Ps conversion (Fantola Lazzarini and Lazzarini, 1991); c is the converter concentration; the overall spin exchange rate constant k SE is 4k CR (see below); c = k c c for reaction of positronide or Ps compound formation, c being the solute concentration; m for the positronide annihilation.…”

Section: •1 Rate Constants Of Positronium Reactions From Observable Quantitiesmentioning

confidence: 99%

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REACTIVITY OF 3d METAL COMPLEXES TOWARDS POSITRONIUM ATOMS

Lazzarini

1999

prog. rct. kin. mech.

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The rate constants of oxidation and spin exchange reactions of positronium, Ps, atoms promoted at various temperatures by numerous 3d complexes are reviewed. The experimental methods used in the field are also described. It is shown that the rate constants of Ps oxidation, kOx, and Ps conversion reactions, kCR, may easily be interpreted on the basis of ligand field theory. In particular, values of kCR were found to be linearly correlated with delocalization of unpaired electrons of the metal ions caused by the ligands, as is described by the ratio β between the inter-electronic repulsion parameters in complexes and in the free gaseous ions. The empirical equation used to estimate β seems to work better than previously believed. This should also be considered an achievement of the experiments reviewed. The main conclusion is that, not only may Ps reactions with 3d complexes be easily interpreted by means of ligand field theory, but that the measurements of k for Ps reactions may, reciprocally, constitute a new method for investigating 3d complexes. Evidence was also found that the same conclusions should also be true for reactions of muonium, Mu.

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Section: •1 Rate Constants Of Positronium Reactions From Observable Quantitiesmentioning

confidence: 99%

“…are altered by this effect. On the basis of eqn 3•16, it was suggested (Fantola- Lazzarini and Lazzarini, 1991) that Ox , or ␥ exp , should be normalized to the viscosity of pure water by multiplying Ox , or ␥ exp , by (c)/(H 2 O); then the corrected values should be plotted vs c to obtain, k D .…”

Section: •2mentioning

confidence: 99%

REACTIVITY OF 3d METAL COMPLEXES TOWARDS POSITRONIUM ATOMS

Lazzarini

1999

prog. rct. kin. mech.

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“…Shortly, the kSE values were obtained from the decay constant λ of the component of the time spectra with the longest meanlife as described in Refs. [2,4].…”

Section: Annihilation Spectramentioning

confidence: 99%

“…Since this was confirmed and the rate constants of diffusion controlled reactions depend on the viscosity coefIicient of the reaction medium and therefore on the reactant concentrations, λ and therefore kSE values are normalised to the viscosity coefficient of pure water as described in Ref. [2]. The viscosity coefficients of the reaction media were measured by means of a KPG Ubbelohde Viscosimeter (B.S.…”

Section: Kinetics Of the Se Conversion Reactionsmentioning

confidence: 99%

“…The rate constants of ortho-into para-Ps conversion reactions, kSE, depend on the particular paramagnetic compound considered, e.g. the kSE's of ammoniated electron (e-am), 3d and 4f aquoions are in the ratio 10:1:0.01 [1,2]. This finding suggested that the kSE 's may depend on the spin density of unpaired electrons at the collision site between Ps and paramagnetic compound.…”

Section: Introductionmentioning

confidence: 99%

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