Charge Dependence of Solvent-Mediated Intermolecular Coster-Kronig Decay Dynamics of Aqueous Ions

The 2s and 2p photoelectron spectra have been measured for Na(+), Mg(2+), and Al(3+) ions in aqueous solution. In all cases, the 2s lines are significantly broader than the 2p features, which is attributed to a shorter lifetime of the respective 2s hole. Since intraionic Coster-Kronig decay channels from the (2s)(-1) state are closed for free Na(+), Mg(2+), and Al(3+) ions, this is evidence for an intermolecular Coster-Kronig-like process, reminiscent of intermolecular Coulombic decay (ICD), involving neighboring water solvent molecules. The observed 2s Lorentzian line widths correspond to lifetimes of the (2s)(-1) state of 3.1, 1.5, and 0.98 fs for the solvated Na, Mg, and Al ions, respectively.