Orienting single-molecule diffraction patterns from XFELs using heavy-metal explosion fragments

Single-molecule imaging is one of the main target areas of X-ray free-electron lasers. It relies on the possibility of orienting the large number of low-counting-statistics 2D diffraction patterns taken at random orientations of identical replicas of the sample. This is a difficult process and the low statistics limits the usability of orientation methods and ultimately it could prevent single-molecule imaging. We suggest a new approach, which avoids the orientation process from the diffraction patterns. We propose to determine sample orientation through identifying the direction of ejection fragments. The orientation of the sample is measured together with the diffraction pattern by detecting some fragments of the Coulomb explosion. We show by molecular-dynamics simulations that from the angular distribution of the fragments one can obtain the orientation of the samples