Retrieval of missing small-angle scattering data in gas-phase diffraction experiments

TL;DR

This paper introduces an iterative phase retrieval algorithm to accurately recover missing low-momentum transfer data in gas-phase ultrafast diffraction experiments, enabling better real-space structural information.

Contribution

The authors develop a novel iterative algorithm that uses real-space constraints and approximate internuclear distances to recover missing diffraction data, improving data completeness.

Findings

Successfully retrieved missing data in simulated and experimental signals.

Enhanced real-space structural information from incomplete diffraction data.

Applicable to ultrafast gas-phase diffraction measurements.

Abstract

We report an iterative algorithm to retrieve accurate real space information from gas phase ultrafast diffraction measurements with missing data at low momentum transfer. The algorithm operates in a manner similar to phase retrieval algorithms which transform signals back and forth between the signal domain and the Fourier transform domain and apply constraints to retrieve the missing phase. Our algorithm retrieves missing data that is not accessible experimentally by applying a real-space constraint that requires only an approximate a-priori knowledge of the shortest and longest internuclear distances in the molecule. We demonstrate successful retrieval of the missing data in simulated data and in experimentally measured electron diffraction signals of photo-dissociated iodobenzene molecules.