Determination of excited state molecular structures from time-resolved gas-phase X-ray scattering

Abstract

We present a comprehensive investigation of a recently introduced method to determine transient structures of molecules in excited electronic states with sub-Ångstrom resolution from time-resolved gas-phase scattering signals. The method,...

Observing the photo-induced structural dynamics of proton transfer in o-nitrophenol by Ultrafast Electron Diffraction

“…In fact, discrepancies between observables highlighted by our independent analyses of experimental and theoretical results would typically be suppressed by tting theoretical predictions to the experimental signal. The use of GSFA has enabled the retrieval of the structural information from the experimental data directly and independently without theoretical input or the tting of experimental data to a large pool of structures generated during molecular dynamics (MD) simulations, 37 and it overcomes the challenge of reconstructing three-dimensional structural information from one-dimensional scattering data. 23-25, 38,39 Crucially, results from the GSFA allow for a unbiased comparison between experiment and simulation, the identi cation of inconsistencies and, therefore, a better benchmark of both investigative modalities.…”

Ultrafast X-ray scattering offers a structural view of excited-state charge transfer

“…These errors are then plotted against each structural parameter such as the interatomic distances and the bond angles. In general, the least-squares error varies as a function of any given structural parameter in a normal-like distribution (25,47). The peak centers of these distributions were thus taken to represent the best-fitting structural parameters.…”

“…The peak centers of these distributions were thus taken to represent the best-fitting structural parameters. This procedure works for any pool of structures that is sufficiently expansive and dense to contain structures in the vicinity of the correct structure (47), and the choice of the Wigner distribution is a matter of convenience.…”

“…An ensemble of one million geometries is sampled from a quantum Wigner distribution at 1,000 K using SHARC software (56) based on the calculated vibrational normal modes of DMP-L + to represent a large range of charge-localized structural space that could potentially be accessed by the molecule in the 3sL state. We use a relatively large scaling temperature (1,000 K) to make sure the displaced geometries are expansive enough to include the target structures (47). Similarly, another ensemble of one million geometries was sampled for the 3sD state.…”

“…The absolute differences between the interatomic distances calculated from the representative structures and corresponding best-fit structural parameters are given as uncertainties in SI Appendix, Table S1, reflecting the uncertainty due to the discrete sampling of the structural space. A comprehensive investigation of various uncertainties when using the structural analysis method was reported in a previous publication (47).…”