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 spectrome ter 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 disp lacement, oil entrainment pumps, are summarised. The problems of handling a nd studying corrosive stable and unstable reactive intermediates, of intere st because of their involvement in atmospheric and combustion chemistry, ar e 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 a dditional constraints on spectrometer design, to enable studies with synchr otron radiation to be performed, are outlined. These involve the need to pr ovide protection for the storage ring optical components from potentially c ontaminating species in a windowless environment, and the need to modify th e pumping philosophy whilst incorporating a facility for angular distributi on 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 attribu ted to the design of the vacuum system which incorporated sample containmen t and differential pumping. (C) 1999 Elsevier Science Ltd. All rights reser ved.