Electron dynamics in charge-transfer-to-solvent states of aqueous chloride revealed by Cl- 2p resonant Auger-electron spectroscopy

Charge-transfer-to-solvent (CTTS) excited states of aqueous chloride are studied by a novel experimental approach based on resonant inner-shell photoexcitation, Cl(-)aq 2p --> e(i), i = 1-4, which denotes a series of excitations to lowest and higher CTTS states. These states are clearly identified through the occurrence of characteristic spectator Auger decays to double Cl 3p valence-hole states, where the CTTS states can be more stabilized as compared to single Cl(-)aq 2p core excitations and optical valence excitations. Furthermore, we have found for the first time that the CTTS electron e(i) bound by a single Cl 2p hole not only behaves as a spectator e(i) --> e'(i), bound by a double valence-hole state before relaxation of the excited electron (i) itself, but also shows electron dynamics to the relaxed lowest state, e(i) --> e'(1*). This interpretation is supported by ab initio calculations. The key to performing photoelectron and Auger-electron spectroscopy studies from aqueous solutions is the use of a liquid microjet in ultrahigh vacuum in conjunction with synchrotron radiation.