Measuring energy-dependent photoelectron escape in microcrystals

Area of Science:

• Crystallography
• Materials Science
• Physics

Background:

• Intense microbeams and microcrystals at synchrotron X-ray sources exacerbate radiation damage.
• Theoretical models predict that photoelectrons, the primary cause of damage, can escape microcrystals.

Purpose of the Study:

• To experimentally validate the theoretical prediction of photoelectron escape from microcrystals.
• To quantify the impact of crystal size and X-ray energy on radiation damage and crystal lifetime.

Main Methods:

• Collected X-ray diffraction data from cryocooled lysozyme microcrystals (5 × 3 × 3 and 20 × 8 × 8 µm) at 13.5 and 20.1 keV.
• Measured absorbed doses using scanning electron microscopy and characterized the X-ray microbeam.
• Quantified crystal lifetime using the D1/2 metric.

Main Results:

• Observed longer crystal lifetimes for smaller crystals.
• Found that crystal lifetime increased at higher X-ray energies.
• Results support theoretical predictions of photoelectron escape, mitigating radiation damage.

Conclusions:

• Photoelectron escape is a significant factor in reducing radiation damage in microcrystals.
• Optimizing detector technology for higher energies (above 20 keV) can exploit this effect.
• Findings guide future synchrotron beamline design for improved data collection.