Resonant elastic x-ray imaging with high intensity ultrafast pulses

Attosecond and femtosecond x-ray free-electron laser pulses have motivated new experimental efforts to enhance scattering efficiency and improve spatial resolution in single-particle imaging experiments by controlling Rabi dynamics of inner-shell electrons and exploiting excited state properties. Motivated by these experimental efforts, we developed a theoretical formalism to model resonant elastic x-ray scattering from an intense ultrafast pulse. In our formalism, the total scattering signal for a single atom response is calculated using a coherent treatment of both resonant fluorescence (A.P)² and elastic scattering (A²) channels. The competing processes of Auger decay and photoionization are also accounted for. The effect of Rabi oscillations on the differential cross section, cross section, and total photon yield is studied on Ne+ system. The total photon yield is found to strongly depend on the pulse area. The choice of pulse area and pulse duration are found to play a role in the amount of structural information that can be obtained from the total scattered signal from a single atom response. The total scattered signals under resonant conditions are found to be an order of magnitude larger than in the case of non-resonant X-ray scattering from pulses of comparable intensities, suggesting that Rabi oscillation can be used to enhance scattering efficiency.