2013, Kornilov, O., Eckstein, M., Rosenblatt, M., Schulz, C.P., Motomura, K., Rouzée, A., Klei, J., Foucar, L., Siano, M., Lübcke, A., Schapper, F., Johnsson, P., Holland, D.M.P., Schlathölter, T., Marchenko, T., Düsterer, S., Ueda, K., Vrakking, M.J.J., Frasinski, L.J.

Single-shot time-of-flight spectra for Coulomb explosion of N2 and I2 molecules have been recorded at the Free Electron LASer in Hamburg (FLASH) and have been analysed using a partial covariance mapping technique. The partial covariance analysis unravels a detailed picture of all significant Coulomb explosion pathways, extending up to the N 4+-N5+ channel for nitrogen and up to the I 8+-I9+ channel for iodine. The observation of the latter channel is unexpected if only sequential ionization processes from the ground state ions are considered. The maximum kinetic energy release extracted from the covariance maps for each dissociation channel shows that Coulomb explosion of nitrogen molecules proceeds much faster than that of the iodine. The N 2 ionization dynamics is modelled using classical trajectory simulations in good agreement with the outcome of the experiments. The results suggest that covariance mapping of the Coulomb explosion can be used to measure the intensity and pulse duration of free-electron lasers.

2017, Feifel, R., Eland, J.H.D., Carniato, S., Selles, P., Püttner, R., Koulentianos, D., Marchenko, T., Journel, L., Guillemin, R., Goldsztejn, G., Travnikova, O., Ismail, I., Miranda, B. Cunha de, Lago, A.F., Céolin, D., Lablanquie, P., Penent, F., Piancastelli, M.N., Simon, M.

Recent advances in X-ray instrumentation have made it possible to measure the spectra of an essentially unexplored class of electronic states associated with double inner-shell vacancies. Using the technique of single electron spectroscopy, spectra of states in CS2 and SF6 with a double hole in the K-shell and one electron exited to a normally unoccupied orbital have been obtained. The spectra are interpreted with the aid of a high-level theoretical model giving excellent agreement with the experiment. The results shed new light on the important distinction between direct and conjugate shake-up in a molecular context. In particular, systematic similarities and differences between pre-edge states near single core holes investigated in X-ray absorption spectra and the corresponding states near double core holes studied here are brought out.