Evidence of sequential interatomic decay in argon trimers obtained by electron-triple-ion coincidence spectroscopy

Sequential interatomic decay, where the first step is an Auger decay with interatomic character and the second step is a pure interatomic Coulombic decay (ICD), is identified in Ar trimers Ar-3. The 2p hole state in Ar3 decays via the L2,3M1M2,3 Auger to the one- site two- hole states Ar++( 3s(-1)3p(-1))-Ar-Ar that couples to the two- site satellite states Ar+(3p(-2)nl)-Ar+(3p(-1))-Ar. These states are subject to ICD to the states Ar+(3p(-1))-Ar+(3p(-1))-Ar+(3p(-1)), in which the nl electron fills the 3p hole in the same Ar site and one of the 3p electrons in the third Ar site is emitted as a slow ICD electron. This ICD process is identified unambiguously by electron-ion-ion-ion coincidence spectroscopy in which the kinetic energy of the slow ICD electron and the kinetic energy release among the three Ar+ ions are measured in coincidence.