A method for exciting free torsional vibrations a spring cantilever, which is clamped in on one side and has a longitudinal extension, of an atomic force microscope (AFM) is disclosed. The invention provides by the one-sidedly clamped-in spring cantilever being placed at a distance over a surface between which and the spring cantilever there is an acoustic coupling medium, by the surface being set into oscillations which are oriented laterally to the surface and are polarized linearly along an oscillation direction, and by the polarization axis given by the oscillation direction being oriented perpendicular to the longitudinal extension of the spring cantilever.