### Abstract

Positron lifetime spectra arising from micellar solutions of sodium dodecylsulphate (SDS) are interpreted in terms of a classical positronium diffusion model published earlier. Unlike the generally accepted assumptions, this model results in a non-exponential ortho-positronium ( omicron -Ps) lifetime density function. A new method is presented for the simultaneous fitting of this lifetime density function to independent lifetime spectra recorded under the same experimental conditions. Among the fit parameters D//p, the diffusion coefficient of omicron -Ps in the solvent (i. e. heavy water) phase is studied in detail; a detailed error analysis for D//p is also given. Provided that the mean aggregation number of SDS micelles is about 60, the published D//p values show that the diffusion coefficient of omicron -Ps in (heavy) water at room temperature is lower than that of small ions and molecules and the Arrhenius plot indicates a strong omicron -Ps localization in the solvent. The hydrodynamic radius of omicron -Ps is calculated.

Original language | English |
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Pages (from-to) | 403-416 |

Number of pages | 14 |

Journal | Radiation Physics and Chemistry |

Volume | 32 |

Issue number | 3 |

Publication status | Published - 1988 |

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### ASJC Scopus subject areas

- Radiation

### Cite this

**INTERPRETATION OF POSITRON LIFETIME SPECTRA ARISING FROM MICELLAR SOLUTIONS. DETERMINATION OF THE ORTHO-POSITRONIUM DIFFUSION COEFFICIENT IN THE SOLVENT.** / Vass, Sz; Kajcsos, Z.

Research output: Contribution to journal › Article

*Radiation Physics and Chemistry*, vol. 32, no. 3, pp. 403-416.

}

TY - JOUR

T1 - INTERPRETATION OF POSITRON LIFETIME SPECTRA ARISING FROM MICELLAR SOLUTIONS. DETERMINATION OF THE ORTHO-POSITRONIUM DIFFUSION COEFFICIENT IN THE SOLVENT.

AU - Vass, Sz

AU - Kajcsos, Z.

PY - 1988

Y1 - 1988

N2 - Positron lifetime spectra arising from micellar solutions of sodium dodecylsulphate (SDS) are interpreted in terms of a classical positronium diffusion model published earlier. Unlike the generally accepted assumptions, this model results in a non-exponential ortho-positronium ( omicron -Ps) lifetime density function. A new method is presented for the simultaneous fitting of this lifetime density function to independent lifetime spectra recorded under the same experimental conditions. Among the fit parameters D//p, the diffusion coefficient of omicron -Ps in the solvent (i. e. heavy water) phase is studied in detail; a detailed error analysis for D//p is also given. Provided that the mean aggregation number of SDS micelles is about 60, the published D//p values show that the diffusion coefficient of omicron -Ps in (heavy) water at room temperature is lower than that of small ions and molecules and the Arrhenius plot indicates a strong omicron -Ps localization in the solvent. The hydrodynamic radius of omicron -Ps is calculated.

AB - Positron lifetime spectra arising from micellar solutions of sodium dodecylsulphate (SDS) are interpreted in terms of a classical positronium diffusion model published earlier. Unlike the generally accepted assumptions, this model results in a non-exponential ortho-positronium ( omicron -Ps) lifetime density function. A new method is presented for the simultaneous fitting of this lifetime density function to independent lifetime spectra recorded under the same experimental conditions. Among the fit parameters D//p, the diffusion coefficient of omicron -Ps in the solvent (i. e. heavy water) phase is studied in detail; a detailed error analysis for D//p is also given. Provided that the mean aggregation number of SDS micelles is about 60, the published D//p values show that the diffusion coefficient of omicron -Ps in (heavy) water at room temperature is lower than that of small ions and molecules and the Arrhenius plot indicates a strong omicron -Ps localization in the solvent. The hydrodynamic radius of omicron -Ps is calculated.

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M3 - Article

VL - 32

SP - 403

EP - 416

JO - Radiation Physics and Chemistry

JF - Radiation Physics and Chemistry

SN - 0969-806X

IS - 3

ER -