Observation of bound states by dissociative attachment

The cross section for the process in Eq. (6.14) is estimated to be 10 18 cm2 [25], A cross section of about two orders of magnitude larger is expected for dissociative attachment to an anion  

This process can be either exo- or endoenergetic depending on magnitudes of relevant bond energies and electron affinities. The threshold is 

Mitroy and coworkers [27] have discussed the use of negative ion beams to measure positron affinities of atoms. The idea is to pass a beam of atomic anions through a swarm of thermal positrons in order to make a positron compound by the charge exchange reaction  

The threshold is the difference of the electron and positron affinities of the species A. Knowledge of the center-of-mass kinetic energy of the colliding species, and the measurement of that of the receding species yields the positron affinity. A competing reaction is Ps formation, but this produces a neutral product A that will not interfere. 

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