The abundance of tetraheptylammonium bromide clusters produced from formami
de solutions by electrospray ionization (ESI) is investigated. It exhibits
a wavy pattern when plotted as a function of cluster size, successive waves
being ordered according to the initial cluster charge z. This structure co
nfirms the ion evaporation mechanism of Iribarne and Thomson and simplifies
drastically the determination of the distribution of cluster charge z and
radius R, from which the kinetics of ion evaporation from charged drops can
be inferred.