Cluster formation by direct laser vaporization: evidence for the twofold mechanism

In this Letter we report experimental evidence relevant to the mechanism of cluster formation by direct laser vaporization of chemical compounds. The mechanism is different due to the type of samples and the type of clusters produced. While the clusters are formed generally through gas-phase recombination reactions, some clusters possess similar stoichiometry to the precursor sample, which, together with the velocity distribution, suggests a direct surface ejection mechanism.