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Abstract
The recent implementation of attosecond and few-femtosecond X-ray pump/X-ray probe schemes in large-scale free-electron laser facilities has opened the way to visualize fast nucleardynamics in molecules with unprecedented temporal and spatialresolution. Here, we present the results of theoretical calculationsshowing how polarization-averaged molecular-frame photoelectronangular distributions (PA-MFPADs) can be used to visualize thedynamics of hydrogen migration in methanol, ethanol, propanol,and isopropyl alcohol dications generated by X-ray irradiation ofthe corresponding neutral species. We show that changes in thePA-MFPADs with the pump−probe delay as a result ofintramolecular photoelectron diffraction carry information on the dynamics of hydrogen migration in real space. Althoughvisualization of this dynamics is more straightforward in the smaller systems, methanol and ethanol, one can still recognize thesignature of that motion in propanol and isopropyl alcohol and assign a tentative path to it. A possible pathway for a correspondingexperiment requires an angularly resolved detection of photoelectrons in coincidence with molecular fragment ions used to define amolecular frame of reference. Such studies have become, in principle, possible since the first XFELs with sufficiently high repetitionrates have emerged. To further support our findings, we provide experimental evidence of H migration in ethanol−OD from ion−ion coincidence measurements performed with synchrotron radiation.