K-shell double core-hole spectroscopy in molecules
1 Laboratoire de Chimie Physique, Matière et Rayonnement, Université Pierre et Marie Curie, 11 rue Pierre et Marie Curie, 75231 Paris Cedex 05, France
2 Permanent address: Department of Physics and Astronomy, Uppsala University, PO Box 516, 751 20 Uppsala, Sweden
Received: 8 June 2013
Revised: 9 August 2013
Published online: 23 October 2013
A great deal of attention has been devoted in the last few years to photoionization processes in isolated molecules leading to the formation of double core-hole (DCH) states. There are two main experimental avenues to induce such processes, namely single-photon absorption followed by the simultaneous ejection of two core electrons, and x-ray-induced multiphoton processes leading to the production of DCH states via the sequential absorption of two soft x- ray photons on a time scale on the order of the molecular Auger lifetime (4–8 femtoseconds for light elements). The formation of molecular two-site (ts) DCH states, in particular, shows great potential as a powerful tool for chemical analysis. A compelling motivation for the study of ts-DCH states is their ability to probe the local chemical environment more sensitively than either single core-hole (SCH) or single-site (ss) DCH states. The enhanced sensitivity originates from the fact that the double ionization potential (DIP) of ts-DCH states is directly coupled to induced changes in the valence charge distribution at the two different atomic sites. Here a review of the recent literature is presented on both types of experiments, and on the related theoretical work.
© EDP Sciences, Springer-Verlag, 2013