2011 February

The gentle impact of quantum mechanics: Non-destructive reflection of fragile helium molecules

Friday, 18th February 2011Publication highlights

Artist’s view of quantum reflection of a diatomic helium molecule in front of a solid surface. The attractive force between the surface and the helium dimer (van-der-Waals force) forms a deep canyon in front of the hard wall. The helium dimer survives this impact, because the dimer actually never comes into this canyon but bounces off the edge of the cliff.

Researchers at the Fritz Haber Institute in Berlin report on the observation of a text-book quantum effect that nicely reveals how counter-intuitive the laws of quantum physics can be. Considering only classical mechanics, a particle moving towards a cliff would, inevitably, fall over (and down) the cliff wall, simply because the force is acting in this direction. In stark contrast, the wave-particle-duality of quantum physics allows for a particle (e.g., an atom or molecule) to bounce back from the edge of the cliff unscathed. This is known as quantum reflection and is responsible for the observation of non-destructive reflection of the weakest bound molecule known, the helium dimer, from a reflection grating. The findings have been published in the journal Science. (more)
(Science, doi: 10.1126/science.1200911)