Investigating two-photon double ionization of D2 by XUV-pump-XUV-probe experiments

We used a split-mirror setup attached to a reaction microscope at the free-electron laser in Hamburg (FLASH) to perform an XUV-pump-XUV-probe experiment by tracing the ultrafast nuclear wave-packet motion in the D-2(+)(1s sigma(g)) with 10 fs time resolution. Comparison with time-dependent calculations shows excellent agreement with the measured vibrational period of 22 +/- 4 fs in D-2(+), points to the importance of accurately knowing the internuclear distance-dependent ionization probability, and paves the way to control sequential and nonsequential two-photon double-ionization contributions.