i-TOF spectra for 800 (blue) and 1000 eV (red) x-ray beams

<p><strong>Figure 3.</strong> i-TOF spectra for 800 (blue) and 1000 eV (red) x-ray beams. The rightmost part of the spectrum is shown on a logarithmic scale to amplify the molecular ion states. Double-sided arrows indicate the TOF distribution width of the fluorine charge states due to their significant KE (see table <a href="http://iopscience.iop.org/0953-4075/46/16/164032/article#jpb469783t1" target="_blank">1</a>).</p> <p><strong>Abstract</strong></p> <p>We investigate the multiphoton ionization and the subsequent fragmentation of SF₆ molecules with intense x-ray-free electron laser pulses at different photon energies. We observe highly charged molecular and atomic ions which were absent in previous experiments with conventional x-ray sources. The observation of fully stripped fluorine ions suggests sequential multiphoton ionization processes with intermediate 1s electron excitation. We measure the average momentum and kinetic energy of each fragment, the comparison of which implies many-body fragmentation pathways of the molecular ions. The observed non-monotonic dependence of the kinetic energy on the charge states of fluorine indicates the multiphoton ionization of 'isolated' atomic neutral fluorine or fluorine ions resultant from bond cleavages and also implies the fragmentation of highly charged molecular ions that are produced at a later time during a single pulse.