Positron binding as a molecular thermometer

Last updated December 4, 2020 by Dermot Green

Wednesday 28 October 3pm
Location: MS Teams
Speaker: Dr Andrew Swann, Queen’s University Belfast


The ability of many atoms and molecules to bind a positron has been recognized for over 20 years. Measurements of positron binding and annihilation have been carried out for around 90 molecules, although on the side of theory, ab initio calculations have proved to be difficult. Here, a model-potential approach is used to calculate the positron binding energy for n-alkanes (C_nH_{2n+2}) and the corresponding cycloalkanes (C_nH_{2n}). For n-alkanes, the dependence of the binding energy on the conformation of the molecule is investigated, with more compact structures showing greater binding energies. As a result, thermally averaged binding energies for larger alkanes (n > 9) show a strong temperature dependence in the range of 100–600 K. This suggests that positron resonant annihilation can be used as a probe of rotational (trans-gauche) isomerization of n-alkanes. In particular, the presence of different conformers leads to shifts and broadening of vibrational Feshbach resonances in the annihilation rate, as observed with a trap-based low-energy positron beam.


We are a Research Cluster of the School of Mathematics and Physics at Queen’s University Belfast in Northern Ireland. Our research interests are focused primarily on computational and theoretical physics.

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