Resolving Multiphoton Processes with High-Order Anisotropy Ultrafast X-ray Scattering

Abstract: We present first results on ultrafast X-ray scattering of strongly driven molecular Iodine and analysis of high-order anisotropic components of the scattering signal, up to four-photon absorption. We discuss the technical details of retrieving high fidelity high-order anisotropy components, and outline a method to analyze the scattering signal using Legendre decomposition. We use simulated anisotropic scattering signals and Fourier analysis to map how anisotropic dissociation motions can be extracted from the various Legendre orders. We observe multitude dissociation and vibration motions simultaneously arising from various multiphoton transitions. We use the anisotropy information of the scattering signal to disentangle the different processes and assign their dissociation velocities on the Angstrom and femtosecond scales de-novo.