22 research outputs found
Ultrafast x-ray scattering and electronic coherence at avoided crossings: complete isotropic signals
Nonadiabatic transitions at conical intersections and avoided crossings play a pivotal role in shaping the outcomes of photochemical reactions. Using the photodissociation of LiF as a model, this theoretical study explores the application of gas phase nonresonant ultrafast x-ray scattering to map nonadiabatic transitions at an avoided crossing, utilizing the part of the scattering signal that probes electronic coherence directly. The presented scattering signals are rotationally averaged and calculated from two- rather than one-electron (transition) densities, which inherently accounts for all possible electronic transitions driven by the x-ray photon. This approach provides quantitative predictions of the experimental signals, thereby facilitating future experimental endeavors to observe nonadiabatic effects and coherent electron dynamics with ultrafast x-ray scattering
Time-resolved X-ray scattering by electronic wave packets: analytic solutions to the hydrogen atom
This paper demonstrates how the time-dependent scattering signal of electronic wave packets in the hydrogen atom can be expressed analytically.</p
Excited Electronic States in Total Isotropic Scattering from Molecules
Ultrafast x-ray scattering experiments are routinely analyzed in terms of the
isotropic scattering component. Here we present an analytical method for
calculating total isotropic scattering directly from ab initio two-electron
densities of ground and excited electronic states. The method is generalized to
compute isotropic elastic, inelastic, and coherent mixed scattering. The
computational results focus on the potential for differentiating between
electronic states and on the composition of the total scattering in terms of
elastic and inelastic scattering. By studying the umbrella motion in the first
excited state of ammonia, we show that the associated electron density
redistribution leaves a comparably constant fingerprint in the total signal
that is similar in magnitude to the contribution from the changes in molecular
geometry