Molecules made of only two Helium atoms (Dimers, He2) and three atoms (Trimers, He3) are extremely fragile, floppy and diffuse quantum objects. The Helium dimer has the by far longest and weakest bond ever observed. It spreads over 100 times the atomic radius. For the trimer an excited halo state, a so called Efimov state, is predicted but not yet found experimentally. We study the fascinating quantum nature of the Helium dimer and trimer experimentally: We ionize them with synchrotron radiation, short laser pulses and hit them with protons and relativistic Uranium ions.

Further information about measurements done so far can be found here:


Ultrafast manipulation of the weakly bound helium dimer
Nat. Phys. 17, 174–178 (2021)

Imaging the He2 quantum halo state using a free electron laser
PNAS 113, 51 (2016)

Observation of the Efimov state of the helium trimer
Science 348, 551 (2015)

Imaging the structure of the trimer systems 4He3 and 3He4He2
Nat. Comm. 5, 5765 (2014)

A molecular movie of interatomic Coulombic decay
Phys. Rev. Lett. 111, 093401 (2013)

The breakup of helium dimers investigated in fast ion collisions
Phys. Rev. A 89, 022704 (2014)
Phys. Rev. Lett. 106, 033201 (2011)

Photoionization of the helium dimer – how to ionize two atoms with a single photon
Phys. Rev. Lett. 104, 153401 (2010)
Phys. Rev. Lett. 104, 133401 (2010)