Safe handling of corrosive chemicals in a vacuum environment: A case study - photoelectron spectroscopy of reactive intermediates

The development of the vacuum system of a gas-phase photoelectron spectrometer is described, which enables prolonged studies of reactive intermediates to be performed. The sample handling and vacuum requirements for gas-phase photoelectron spectroscopy studies of stable molecules using positive displacement, oil entrainment pumps, are summarised. The problems of handling and studying corrosive stable and unstable reactive intermediates, of interest because of their involvement in atmospheric and combustion chemistry, are then highlighted. Methods of generation, transportation and localization of reactive species within a spectrometer, with emphasis on minimising the contamination of the electron optics of the instrument are discussed. The additional constraints on spectrometer design, to enable studies with synchrotron radiation to be performed, are outlined. These involve the need to provide protection for the storage ring optical components from potentially contaminating species in a windowless environment, and the need to modify the pumping philosophy whilst incorporating a facility for angular distribution studies. A prototype spectrometer design is described and some examples of continuous studies of reactive intermediates with this spectrometer are presented. The extended operational lifetime of the spectrometer is attributed to the design of the vacuum system which incorporated sample containment and differential pumping. (C) 1999 Elsevier Science Ltd. All rights reserved.