• On the surface the ammonia molecule is bound via the nitrogen atom to the surface, the hydrogen atoms are pointing away from the surface.
• Initially the ammonia molecules vibrates with respect to the surface, and the hydrogen atoms in the molecule vibrate with respect to the nitrogen atom.
• The laser excitation initiates that the hydrogen atoms move towards the surface, since the molecule starts to adopt a planar geometry.
• After the excitation has decayed the hydrogen atoms continue their motion until the hydrogen atoms are closer to the surface than the nitrogen atom
• The repulsion between the hydrogen atoms and the surface atoms pushes the whole molecule away from the surface.
• The molecule leaves the surface with the hydrogen atoms pointing towards the surface. The extend of vibration in the molecule has increased, i.e. it has been vibrationally excited.

The movie has been prepared using the graphics software IGOR from WaveMetrics.