A Phenomenological Description of the PALS Response in Glass - Forming Systems |
| Journal |
Materials Science Forum (Volume 607) |
| Volume |
Positron and Positronium Chemistry |
| Edited by |
S. J. Wang, Z. Q. Chen, B. Wang and Y. C. Jean |
| Pages |
48-52 |
| DOI |
10.4028/www.scientific.net/MSF.607.48 |
| Online since |
November, 2008 |
| Authors |
Josef Bartoš
|
| Keywords |
Glass-Forming Compounds, Phenomenological Description, Positron Annihilation Lifetime Spectroscopy (PALS), Viscosity |
| Abstract |
A phenomenological description of the ortho-positronium (o-Ps) response from positron annihilation spectroscopy (PALS) and the dynamics from viscosity studies on two typical glass-forming compounds within the framework of the two-order parameter (TOP) model is presented. The dynamical data are accounted for by the modified Vogel – Fulcher – Tamman - Hesse (M-VFTH) equation. Subsequently, the quasi-sigmoidal course of the o-Ps lifetime, τ3, with or without the high-temperature plateau region as a function of the temperature over a wide temperature range can be described by an effective free volume version of the TOP model. This simultaneous description suggests a close relationship between the PALS response and the dynamics of supercooled liquids and seems to support the liquid - like and solid - like domain physical picture of all the three physical states of the disordered phase of the condensed systems. |
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