21 research outputs found
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
Towards high-resolution X-ray scattering as a probe of electron correlation
X-ray scattering cross sections are calculated using a range of increasingly correlated methods: Hartree–Fock (HF), complete active space self-consistent field (CASSCF), Monte Carlo configuration interaction (MCCI), and full configuration interaction (FCI). Even for the seemingly straightforward case of ground state Ne, the accuracy of the total scattering is significantly better with a more correlated wavefunction. Scanning the bond distance in ground state CO shows that the total scattering signal tracks the multireference character. We examine the convergence of the elastic, inelastic, and total scattering of O3. Overall, the inelastic and total components are found to be the most sensitive to the strength of correlation. Our results suggest that highly accurate measurement of X-ray scattering could provide a sensitive probe of pair-wise correlation between electrons.</p