Gas phase photoionisation studies provide a diverse wealth a phenomena which need to be investigated to further our understanding of ionisation mechanisms, many of which are important in atmospheric photo-reactions and in plasmas. In our case we employ synchrotron radiation, which produces vacuum ultra-violet (VUV) light in the 15-150eV range, and we measure the energy and angular distributions of photoelectrons emitted from photoionisation of rare gas atoms and small molecules. In particular, a photoelectron-photoelectron coincidence spectrometer has been developed to investigate photodouble ionisation (PDI) as single energetic photons can multiply ionise atoms and molecules. The spectrometer can also operate in a variety of other modes that investigate single ionisation processes. They include:

• Threshold Photoelectron Spectroscopy - where one detects 'zero' energy electrons.
• 2D Photoelectron spectroscopy - where one obtains a broad perspective on resonance decay routes to various possible ionic states.
• Angle-resolved Photoelectron Spectroscopy - where the angular distributions are measured simultaneously using the merits of toroidal analysers.