Fig. 1: Schematic diagram of resonant ICD processes in solvated calcium.
From: The solvation shell probed by resonant intermolecular Coulombic decay
a Regular photoelectron spectroscopy probes electrons emitted from any molecule in the solution. The purple wave arrow represents an incoming photon and the orange arrow represents an outgoing electron. b In resonant ICD, electrons are emitted specifically from the solvation shell of the excited Ca2+ ion. The first step is the resonant excitation of Ca 2p electrons to empty 3d orbitals. In the second step, ICD relaxation occurs by energy transfer and ionization of a neighbouring water molecule (or counter-ion X−). One can distinguish between the participator case (the excited electron fills the 2p hole) and the spectator case (another calcium valence electron fills the 2p hole). The emitted ICD electron has a different kinetic energy for the two processes.
