Positron attachment to molecules

Abstract

AbstractAt incident positron energies below the threshold for positronium atom formation annihilation rates for molecules are much larger than those expected on the basis of simple two‐body collisions. We now understand that this phenomenon is due to positron attachment to molecules mediated by vibrational Feshbach resonances. This attachment enhances greatly the overlap of the positron and the molecular electron wave functions and hence increases the probability of annihilation. Annihilation spectra as a function of incident positron energy yield measurements positron‐molecule binding energies. Using this technique, to date, positron‐molecule binding energies for thirty molecules have been measured. This paper presents a brief review of our current understanding of this process, the significance of these results, and outstanding questions for future research. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)