Outrunning damage: Electrons vs X-rays-timescales and mechanisms

Area of Science:

• Structural biology
• Biophysics
• Materials science

Background:

• Ahmed Zewail's late-career interest in fast electron spectroscopy and imaging aimed to achieve radiation-damage-free molecular movies.
• Diffract-and-destroy experiments are crucial for imaging biological samples at the molecular level.

Purpose of the Study:

• To compare the atomistic mechanisms of sample destruction in diffract-and-destroy experiments using high-energy electron beams versus X-ray laser pulses.
• To evaluate the feasibility of using electron beams for molecular imaging with reduced radiation damage.

Main Methods:

• Comparative analysis of damage mechanisms and timescales for electron beam and X-ray laser irradiation.
• Calculation and comparison of elastic, inelastic, and photoelectron cross sections.
• Assessment of inelastic mean-free paths for low-energy electrons in insulators relative to bioparticle size.

Main Results:

• Electron beam irradiation exhibits significantly lower dose and structural damage rates compared to X-ray laser pulses.
• Electron scattering provides a unique method for tracking nuclear motion during sample explosion.
• Reduced damage and larger elastic scattering cross sections in electron diffraction are advantageous, despite challenges with Coulomb interactions.

Conclusions:

• Electron beams offer a promising alternative to X-rays for single-particle diffraction, with reduced radiation damage.
• Further development in reducing emittance growth due to Coulomb interactions is necessary for intense, sub-micron electron beams for molecular imaging.