4 December 2023
Henry Chapman, DESY
Serial crystallography and diffraction with XFEL pulses
One of the motivating ideas behind the development of X-ray free-electron lasers is to obtain atomic structures of biological macromolecules without having to crystallise them or cool them to cryogenic temperatures. These facilities produce pulses of X-rays that are over a billion times brighter than available at synchrotron sources, with around 10^12 photons in a pulse of tens of femtoseconds. When focused to small dimensions such pulses are destructive and completely ionise and vaporise any sample, but the short duration of the pulse can outrun these processes to give pristine images at doses many thousands of times greater than usually can be tolerated. The first demonstration of this “diffraction before destruction” was made at the FLASH soft X-ray FEL, and then later tested at atomic resolution at the LCLS using protein crystals, opening up the field of serial femtosecond crystallography. Reducing the size of samples down to single molecules has proved more challenging due to competing background noise and the consequent need to record millions of diffraction patterns. Recent progress at the European XFEL shows that these issues can be addressed, with the demonstration of millions of single-particle diffraction patterns recorded from nanoparticles.
