Fragmentation Kinetics of Icosahedral Clusters: Ar-12(Ar) and Ar-12(Ar+)

摘要

We study the fragmentation kinetics of icosahedral Ar-12(Ar) and Ar-12(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 similar to 20% and weakly dependent on temperature, whereas that of neutral clusters is less efficient but shows moderate temperature dependence. The dominant products from Ar-12(Ar+) are 10-Ar and 9-Ar clusters, but a wider size distribution is found for Ar-12(Ar) with the principal products 11- and 10-Ar clusters. The fragmentation of Ar-12(Ar+) occurs on two timescales; rapid fragmentation at short time with rate coefficients similar to 3 x 10(11)/s, and slow process at long time with similar to 2 x 10(10)/s. In neutral clusters, the extent of fragmentation is low during the early period with rate coefficients similar to 5 x 10(9)/s. The fragmentation dynamics is distinctly different from Ar-12(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.