facilities, should not yet be ruled out. The theory we present opens up new experimental avenues to measure the impact of damage on single particle diffraction, which is needed to test damage models and to identify optimal imaging conditions.'
author:
- 'Andrew V. Martin'
- 'Justine K. Corso'
- Carl Caleman
- Nicusor Timneanu
- 'Harry M. Quiney'
bibliography:
- 'damage\_effects.bib'
title: ' Single molecule imaging with longer x-ray laser pulses '
---

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Introduction
============

X-ray free-electron laser (XFEL) pulses are envisioned to probe the structures of radiation-sensitive samples, like biological molecules, by outrunning radiation damage processes[@Neutze2000]. Current facilities, however, produce their brightest pulses with durations of the order of tens of femtoseconds[@LCLS; @Ishikawa2012], which is sufficient time for ionization to become widespread and for ions to move several [Å]{}ngstr[ö]{}ms[@Caleman2009; @Caleman2011]. In spite of this, the first applications of XFELs to serial crystallography have been highly successful[@Chapman2011; @Boutet2012]. It turns out that even for longer pulses ($\sim$ 50–100 fs), Bragg diffraction probes the undamaged structure in the first few femtoseconds of the pulse-sample interaction, turning off at later times when radiation damage distributes the diffraction signal as a diffuse background[@Barty2012]. In this way, XFEL Bragg diffraction is effectively 