Evidence for an alignment effect in the motion of swift ion clusters through solids

Distributions in angle and in energy have been measured for ions transmitted through thin solid targets bombarded by various molecular-ion beams. The results, which differ markedly from those expected from simple Coulomb explosions, indicate that for the ion clusters created inside the target, the internuclear vectors tend to align with the beam direction. An explanation is suggested in terms of a wake potential generated behind each particle as it traverses the solid