Positron annihilation spectroscopy is used to characterize the ortho-positronium lifetime, τ₃, in a broad range of small molecule organic glasses over a wide temperature range. The magnitude and thermal variations of τ₃ reflect changes in the dielectric α-relaxation time τ_α and its non-Arrhenius or ``fragile'' characteristics. τ₃ also displays striking similarities with the fast relaxations reflected in the hydrogen-weighted mean square atomic displacements 〈u²〉. The parallel temperature variations of 〈u²(T/Tg)〉, τ₃(T/Tg), and τ_α(T/Tg), and their similar patterns of change between the different glasses, are discussed in terms of anharmonicity in the intermolecular caging potentials and the subnanometer density heterogeneities.
No takes yet. Share an insight, caveat, or question.
Ngai et al. (2001) studied this question.
Synapse has enriched 5 closely related papers on similar clinical questions. Consider them for comparative context: