High-gain free-electron lasers (FELs) operating at X-ray wavelengths have the potential to gather incredibly detailed information on how matter interacts and arranges itself at atomic and molecular scales. Output from a FEL can be a factor of around 108 brighter than current synchrotron sources (providing 108 times as many useful photons), and X-ray FELs should yield detailed structural information about molecules, atoms and their electronic states much more efficiently than current synchrotron X-ray sources. If high-brightness X-ray pulses of sufficiently short duration (around 10-15-10-17 s) can be generated, it may also be possible to capture ephemeral events, such as molecular bond formation, without temporal blurring. In essence, we would be able to make 'molecular movies'. Of course, the ability to observe phenomena at these scales also offers the enticing prospect of being able to control them. Recent progress towards these dreams has been made on a prototype of a Japanese X-ray FEL (XFEL) - the SPring-8 Compact SASE Source (SCSS) - and is reported on page 555 of this issue1. © 2008 Macmillan Publishers Limited.
- high-gain free-electron lasers (FELs)
- X-ray wavelengths
- atomic and molecular scales