Abstract
On the example of the giant helium dimer, we present an efficient electronic decay process for excited atoms or molecules embedded in a chemical environment, called Interatomic (intermolecular) Coulombic decay (ICD). After simultaneous ionization and excitation of a helium atom within a helium dimer, the excited ion relaxes by ICD to He+(1s) and the neighbor neutral helium is ionized to He+(1s) as well and emits a secondary electron.
A short review on ab initio methods developed during the last 10 years to accurately describe ICD is reported. Finally, the main striking results on the helium dimer obtained experimentally and theoretically are summarized.