Molecules seen rebounding before they hit a surface: "Although the helium moved quickly, it was sent towards the target at a glancing angle – just 0.02� – meaning it would impact with very little energy. The team found that the dimers and trimers rebounded when they were still tens of nanometres away from the target's surface.
They also stayed intact afterwards, without breaking up into individual helium atoms. 'When we saw the dimer reflection we were surprised, because it is very fragile,' Zhao says. The helium atoms in a dimer are bound together with 100 million times less energy than two bound hydrogen atoms, a connection so tenuous it has been dubbed 'the weakest bond'."