elationship between the non linear dynamic behaviour of an cillating tip–microlever system and the contrast at the atomic scale

this paper, the dynamic behaviour of an oscillating tip–microlever system at the proximity of a surface is discussed. ttractive tip–surface interaction is simply described with a Van der Waals dispersive term and a sphere–plane try. We show that the non linear behaviour of the oscillator is able to explain the observed shifts of the resonance ncy as a function of the tip–surface distance without the need of introducing a particular short range force. q