Computational studies of the x-ray scattering properties of laser aligned stilbene

Towards high-resolution X-ray scattering as a probe of electron correlation

We demonstrate that X-ray scattering can be used as a probe of electron–electron correlation.

Ab Initio Calculation of Total X-ray Scattering from Molecules

We present a method to calculate total X-ray scattering cross sections directly from ab initio electronic wave functions in atoms and molecules. The approach can be used in conjunction with multiconfigurational wave functions and exploits analytical integrals of Gaussian-type functions over the scattering operator, which leads to accurate and efficient calculations. The results are validated by comparison to experimental results and previous theory for the molecules H₂ and CO₂. Importantly, we find that the inelastic component of the total scattering varies strongly with molecular geometry. The method is appropriate for use in conjunction with quantum molecular dynamics simulations for the analysis of new ultrafast X-ray scattering experiments and to interpret accurate gas-phase scattering experiments.

Imaging rotations and vibrations in polyatomic molecules with X-ray scattering

An approach for calculating elastic X-ray scattering from polyatomic molecules in specific electronic, vibrational, and rotational states is presented, and is used to consider the characterization of specific states in polyatomic molecules using elastic X-ray scattering.

Elastic X-ray scattering from state-selected molecules

The characterization of electronic, vibrational, and rotational states using elastic (coherent) X-ray scattering is considered. The scattering is calculated directly from complete active space self-consistent field level ab initio wavefunctions for H₂ molecules in the ground-state X¹Σ_g⁺ and first-excited EF¹Σ_g⁺ electronic states. The calculated scattering is compared to recent experimental measurements [Y.-W. Liu et al., Phys. Rev. A 89, 014502 (2014)], and the influence of vibrational and rotational states on the observed signal is examined. The scaling of the scattering calculations with basis set is quantified, and it is found that energy convergence of the ab initio calculations is a good indicator of the quality of the scattering calculations.

Ab Initio Calculation of Molecular Diffraction

We discuss the application of ab initio X-ray diffraction (AIXRD) to the interpretation of time-resolved and static X-ray diffraction. In our approach, elastic X-ray scattering is calculated directly from the ab initio multiconfigurational wave function via a Fourier transform of the electron density, using the first Born approximation for elastic scattering. Significant gains in efficiency can be obtained by performing the required Fourier transforms analytically, making it possible to combine the calculation of ab initio X-ray diffraction with expensive quantum dynamics simulations. We show that time-resolved X-ray diffraction can detect not only changes in molecular geometry but also changes in the electronic state of a molecule. Calculations for cis-, trans-, and cyclo-butadiene, as well as benzene and 1,3-cyclohexadiene are included.