Comment on “ Semiemperical Approach to Positron Annihilation in Molecules


One of the outstanding results of positron scattering is the very large annihilation rates for the organic molecules [1]. In a recent Letter, Laricchia and Wilkin [2] postulated that the large values of Zeff were caused by two mechanisms. First, the length of time a virtual positronium (Ps) cluster would remain in the vicinity of an atom or molecule during the collision was estimated to get increasingly larger as the ionization potential approached 6.80 eV. This aspect of their Letter is not discussed in this Comment. The discussion of the second factor can be simplified by referring to the electron that is part of a real or virtual Ps cluster as the cluster electron. The other electrons of the atom or molecule can be called the spectator electrons. Laricchia and Wilkin suggested that the pickoff annihilation rate Gpo, with the spectator electrons, was much larger than the direct annihilation rate with the cluster electron due to strong electron-positron correlations with the spectator electrons. The cluster annihilation rate Gc is the spin-averaged rate of Ps ground state, i.e., 2 3 109 s21. The pickoff rate (in s21) was estimated to be

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@inproceedings{Mitroy1999CommentO, title={Comment on “ Semiemperical Approach to Positron Annihilation in Molecules}, author={J . Mitroy and G . G . Ryzhikh and Martti J Puska}, year={1999} }