(Bio)Chemical science at XFELs – Implications from thinking through a science case

We have been using X-ray radiation from synchrotron and X-ray free-electron laser sources a lot for probing molecules in the gas phase and in solution. And the question is: Why? I will try here to give one possible answer to this question by presenting a case where we think that X-ray measurements, spectroscopy in this case, could make a difference. This may help others to find out why they should be using X-rays in future projects.