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.

2015, Klinker, M., Trabattoni, A., González-Vázquez, J., Liu, C., Sansone, G., Linguerri, R., Hochlaf, M.., Klei, J., Vrakking, M.J.J., Martin, F., Nisoli, M., Calegari, F.

We wish to understand the processes underlying the ionization dynamics of N2 as experimentally induced and studied by recording the kinetic energy release (KER) in a XUV-pump/IR-probe setup. To this end a theoretical model was developed describing the ionization process using Dyson Orbitals and, subsequently, the dissociation process using a large set of diabatic potential energy surfaces (PES) on which to propagate. From said set of PES, a small subset is extracted allowing for the identification of one and two photon processes chiefly responsible for the experimentally observed features.