Multi-wavelength anomalous diffraction at high x-ray intensity

TL;DR

This paper extends the multi-wavelength anomalous diffraction (MAD) method to high-intensity x-ray regimes, accounting for electronic damage, and demonstrates its potential for rapid, ab initio nanocrystal structure determination using x-ray free-electron lasers.

Contribution

It introduces a generalized MAD approach suitable for high x-ray intensities, including a new theoretical framework and damage dynamics analysis.

Findings

Existence of a high-intensity MAD Karle--Hendrickson equation

Electronic damage can enhance phasing effectiveness

Potential for femtosecond nanocrystallography

Abstract

The multi-wavelength anomalous diffraction (MAD) method is used to determine phase information in x-ray crystallography by employing dispersion corrections from heavy atoms on coherent x-ray scattering. X-ray free-electron lasers (FELs) show promise for revealing the structure of single molecules or nanocrystals within femtoseconds, but the phase problem remains largely unsolved. Due to the ultrabrightness of x-ray FEL, samples experience severe electronic radiation damage, especially to heavy atoms, which hinders direct implementation of the MAD method with x-ray FELs. We propose a generalized version of the MAD phasing method at high x-ray intensity. We demonstrate the existence of a Karle--Hendrickson-type equation for the MAD method in the high-intensity regime and calculate relevant coefficients with detailed electronic damage dynamics of heavy atoms. Our results show that the bleaching effect on the scattering strength of the heavy atoms can be advantageous to the phasing method. The present method offers a potential for \textit{ab initio} structural determination in femtosecond x-ray nanocrystallography.