Inner-shell multiple ionization of polyatomic molecules with an intense x-ray free-electron laser studied by coincident ion momentum imaging

The ionization and fragmentation of two selenium containing hydrocarbon molecules, methylselenol (CH3SeH) and ethylselenol (C2H5SeH), by intense (>10(17) W cm(-2)) 5 fs x-ray pulses with photon energies of 1.7 and 2 keV has been studied by means of coincident ion momentum spectroscopy. Measuring charge states and ion kinetic energies, we find signatures of charge redistribution within the molecular environment. Furthermore, by analyzing fragment ion angular correlations, we can determine the laboratory-frame orientation of individual molecules and thus investigate the fragmentation dynamics in the molecular frame. This allows distinguishing protons originating from different molecular sites along with identifying the reaction channels that lead to their emission.