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Correlation of Positron Annihilation and Other Dynamic Properties in Small Molecule Glass-Forming Substances

Published

Author(s)

K L. Ngai, L R. Bao, Albert F. Yee, Christopher Soles

Abstract

Positron annihilation lifetime spectroscopy (PALS) measurements are performed on four widely studied small molecule glass-formers (ortho terphenyl, glycerol, propylene glycol and propylene carbonate) over a wide temperature range above and below the glass transition. The magnitudes and thermal variations of the ortho-positronium lifetimes $\tau_3}$ show a strong resemblance to well established trends with the structural $\alpha$-relaxation time $\tau_\alpha}$ and its non-arrhenius or 'fragile' characteristics. Furthermore, the thermal variations of $\tau_3}$ show striking similarities with the fast relaxations that are reflected the mean square displacement $$, obtained by incoherent neutron scattering. The parallel temperature variations of $$, $\tau_3}(T/T_g})$, and $\tau_\alpha}(T/T_g})$, and their similar patterns of change between different organic glass-forming liquids, is discussed in terms of the anharmonicity of the intermolecular caging potential and the sub-nm density heterogeneities evidenced by PALS.
Citation
Physical Review Letters
Volume
87
Issue
No. 21

Keywords

anharmonic vibrations, glass dynamics, mean-square displament, neutron scattering, positron annihilation

Citation

Ngai, K. , Bao, L. , Yee, A. and Soles, C. (2001), Correlation of Positron Annihilation and Other Dynamic Properties in Small Molecule Glass-Forming Substances, Physical Review Letters (Accessed February 24, 2024)
Created October 31, 2001, Updated October 12, 2021