Imaging electron-density fluctuations by multidimensional X-ray photon-coincidence diffraction.
The ultrafast spontaneous electron-density fluctuation dynamics in molecules is studied theoretically by off-resonant multiple X-ray diffraction events. The time- and wavevector-resolved photon-coincidence signals give an image of electron-density fluctuations expressed through the four-point correlation function of the charge density in momentum space. A Fourier transform of the signal provides a real-space image of the multipoint charge-density correlation functions, which reveal snapshots of the evolving electron density in between the diffraction events. The proposed technique is illustrated by ab initio simulations of the momentum- and real-space inelastic scattering signals from a linear cyanotetracetylene molecule.
['Ye|Lyuzhou|L|', 'Rouxel|Jérémy R|JR|', 'Cho|Daeheum|D|', 'Mukamel|Shaul|S|0000-0002-6015-3135']
photon-coincidence X-ray diffraction multidimensional spectroscopy