The collection efficiency of ions with identical mass by charge ratio is limited in our experiment because of dead time effects. Due to the inherent kinetic energy spread caused due to CE, it is difficult to separate ions with similar mass by charge ratio. This applies to events corresponding to cleavage of central C-C bond of the butadiene molecule when fragment ions of the kind C 2 H + n (n = 0 to 3) and C 2 H + m (m = 0 to 4) are detected in coincidence. Thus, we will not discuss the relative contributions of such fragmentation channels quantitatively.