Multiple photoionisation in the rare gases from threshold to 280 eV

A time-of-flight spectrometer has been coupled with a source of synchrotron radiation to measure the photoionisation cross sections for multiple ionisation of the rare gases He to Xe in the photon energy range 50-280 eV. Comparison is made with theoretical calculations both in the case of double ionisation of He, Ne and Ar and in the case of single ionisation of Kr and Xe, where electron correlation effects are supposed to enhance the various cross sections. The importance of an accurate knowledge of monochromator scattered light in such experiments is emphasised.