Rotational coherence as an alternative to coincidence techniques at x-ray free electron lasers

We demonstrate an alternative approach to coincidence particle detection, based on impulsive rotational Raman excitation, for molecular frame measurements at x-ray FELs. A train of 8 infrared laser pulses induces the lab-frame observable coherence. At a field-free alignment revival, we register the angle-resolved laboratory frame Auger and photo-electron spectral feature variations with the tumbling molecular body frame. The time and angle dependence of the electron emission patterns that constrain theory are amenable to large numbers of interactions per pulse and, more importantly, has no axial recoil requirement for kinematic reconstruction. We see this as a method to bypass experimental challenges at XFELs by accepting