Fragmentation of ionized liquid helium droplets:: A new interpretation

Pure liquid helium droplets of mean size [N] = 100-15000 atoms ionized by electron impact show surprisingly similar ion fragment distributions. For all cluster sizes He-2(+) is the most probable cluster ion fragment, accounting for 30%-70% of the total ion yield. The high relative intensity of He-2(+) for the larger clusters shows that the droplets dissipate the ionization energy through an impulsive process, which ejects He-2(+) from me cluster, rather man by thermal evaporation. The other helium ion fragments that have been the focus of previous studies ate most likely formed by a similar mechanism. (C) 1998 American Institute of Physics. [S0021-9606(98)00547-9].