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This study deals with the initial oxidation of some 3d metal clusters in gas phase. In the experiments neutral metal clusters in a supersonic beam are made to collide with one or a few oxygen molecules in a reaction cell. The reaction products are detected with photoionization and mass spectrometry. By comparing the abundance of unreacted and reacted clusters, absolute sticking probabilities (S) can be determined. Transition metals with open d shells, e.g. Ni, have high, almost constant S for O2 on clusters containing more than 20 atoms. The size evolution of S for Cu, on the other hand, shows repeated minima and maxima. Cluster sizes which have high ionization potentials (IPs) and closed electronic shells, according to the spherical jellium model, are the ones with the lowest S. The IPs of CunO2 clusters have also been investigated. Compared with the IPs of the pure Cu clusters, the IPs of the oxidized clusters are generally higher and the large drops at the shell openings are less distinct.

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Clusters of iron produced in a laser vaporization source have been characterized with time‐of‐flight spectra and deposited on different substrates for production of films of varying thickness. The magnetic properties of these films with thicknesses of 60 and 120 nm were investigated using an alternating gradient magnetometer. The films exhibit mono‐domain behavior from a broad size distribution which has been confirmed by transmission electron microscopy. Films were also investigated by Mössbauer spectroscopy, which showed fast relaxation in the particles at room temperature. © 1998 John Wiley & Sons, Ltd.

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