Interatomic Coulombic decay in helium nanodroplets

Interatomic Coulombic decay (ICD) is induced in helium nanodroplets by photoexciting the n = 2 excited state of He+ using XUV synchrotron radiation. By recording multiple-coincidence electron and ion images we find that ICD occurs in various locations at the droplet surface, inside the surface region, or in the droplet interior. ICD at the surface gives rise to energetic He+ ions as previously observed for free He dimers. ICD deeper inside leads to the ejection of slow He+ ions due to Coulomb explosion delayed by elastic collisions with neighboring He atoms, and to the formation of He-k(+) complexes.