Vacuum ultraviolet beamline at the Swiss Light Source for chemical dynamics studies

A bend-magnet vacuum ultraviolet (VUV) beamline, intended for chemical dynamics studies, was constructed and brought into operation at the Swiss Light Source (SLS) of the Paul Scherrer Institut. The beamline delivers synchrotron radiation in the 5–30 eV photon energy range with a photon flux of 1011 photons/s at 10 eV and 1012 photons/s at 20 eV with a resolving power of 2500. The resolving power increases to 104 at the cost of photon flux. An in-house designed rare gas filter is used to suppress higher harmonic radiation by a factor of >104, yielding purely monochromatic light in the energy range of 5–21.6 eV. The filter is compact, easy to align, requires a total pumping power of less than 645 l/s and consumes only 3 normal l/h of filter gas. It is located at the end of the beamline, right in front of the experimental endstation. It is usually operated at a higher pressure than the endstation, which offers the additional benefit of protecting the beamline vacuum from sample contamination.