Magneto-Optical Investigation of Mn and Cu-Mn Small Clusters Embedded in Rare Gas Matrices

Among the techniques which are used to probe the structure and the electronic properties of small metal particles, the measurement of the differential absorption of polarized light under an applied magnetic field is one of the most sensitive. Used in conjunction with absorption the magnetic circular or linear dichroism (MCD or MLD) can provide a crucial check of the ground or excited states of clusters1. Since the density of small metal particles in a free jet is usually too small to allow absorption measurements in the gas phase, the particles can be trapped in rare gas matrices where they experience the smallest perturbation relative to the gas phase. However the matrix is not inert and it can interact with the atoms2 or the clusters3 depending upon the vibrational coupling with rare gas “cage”2 or the different trapping sites3. It is also known that thermal sources produce mostly a beam of atoms and different set-ups have been used to increase the amount of clusters in the emitted beam4. Obviously the best way to obtain clusters of selected size is to mass select the particles after they have been produced with sufficient intensity using a sputtering device5. Since such a technique was not available to us we used a thermal source and allowed the metal particles to interact in a cold tube before trapping them in argon and krypton matrices.