Fragmentation Kinetics of Icosahedral Clusters: Ar12(Ar) and Ar12(Ar+)

Abstract

We study the fragmentation kinetics of icosahedral Ar12(Ar) and Ar12(Ar+) clusters in the temperature range 10–300 K, using a classical dynamics method for detailed forms of host–host and host–guest interaction energies composed of short‐ and long‐range terms. The fragmentation of host atoms in charged clusters is ~20% and weakly dependent on temperature, whereas that of neutral clusters is less efficient but shows moderate temperature dependence. The dominant products from Ar12(Ar+) are 10‐Ar and 9‐Ar clusters, but a wider size distribution is found for Ar12(Ar) with the principal products 11‐ and 10‐Ar clusters. The fragmentation of Ar12(Ar+) occurs on two timescales; rapid fragmentation at short time with rate coefficients ~3 × 1011/s, and slow process at long time with ~2 × 1010/s. In neutral clusters, the extent of fragmentation is low during the early period with rate coefficients ~5 × 109/s. The fragmentation dynamics is distinctly different from Ar12(Ar+), which is attributed to an escaping host atom promoting the dissociation of neighbors, a host–host cooperative effect leading to a sigmoidal rise of fragmentation. The effect is present in the temperature range 100–300 K. Fragmentation kinetics of neutral clusters is discussed in detail.