Fragmentation of large ionized clusters of rare gas atoms

Abstract

Molecular dynamics is used to examine the fragmentation of clusters of rare gas atoms after ionization. The cohesive energy is given by a quantum mechanical model with a delocalized hole. Very small clusters dissociate entirely into single atoms and a positively charged dimer. Larger clusters (e.g. Ne13, Xe13 and Ne55) first eject rapid atoms, then thermalize and evaporate further atoms, which strongly decreases their size. Very large clusters (e.g. Xe55) are only heated up after ionization and do not loose atoms. Thus the peaks in mass spectra do not show the atomic shell structure of neutral clusters up to rather large cluster sizes. Instead the stability of ionized clusters is reflected.