The thermally induced isomerization of neutral silicon clusters has been studied by a molecular beam experiment, investigating velocity slip distributions with a time-of-flight method. The clusters dispersed in helium flow through a heated tube and, at its end, expand into vacuum. The observed velocity distributions can be explained by the existence of a cylindrical and a spherical class of isomers, whose relative intensities can be examined in dependence of the tube temperature. Assuming that the isomerization can be described by a unimolecular gas-phase reaction, one is able to derive a rate constant for the isomerization. The results are analyzed within the activated complex theory and give evidence, that entropic effects play a crucial role for the cluster isomerization reaction.
Founded in 1887, the Zeitschrift für Physikalische Chemie covers the main developments in physical chemistry, placing with an emphasis on experimental research. It represents a combination ofdiscusses reaction kinetics and spectroscopy, surface research and electrochemistry, thermodynamics and the structure analysis of matter in its various conditions, among other topics.