Mass-Selection and Soft-Landing

All cluster sources presently employed generate a more or less broad distribution of clusters of different sizes. Therefore, in order to investigate and exploit the size-dependent cluster properties, the application of mass-selection 

In the remainder of this section, we will therefore focus on the interaction of mass-selected cluster beams with solid surfaces. 

A further less commonly employed but very classical method for mass-selection is the Wien-filter which combines an electrostatic and a magnetic field for mass-selective cluster deflection. This device is applied in particular with the purpose to obtain large cluster currents for cluster-surface interaction and deposition experiments at moderate resolution [75, 76]. Another approach for size-selection in combination with a sputter source ]47] or a laser vaporization source [61,77,78] has been chosen recently. In both cases, a magnetic dipole field has achieved the size-selection. Subsequent deceleration of the size-selected clusters to less than 1 eV per atom enables soft-landing under UHV conditions [47]. Monodispersed chromium cluster beam densities range from 0.1 to 5nA mm, depending on the cluster size ]47]. 

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